200 Litre Direct Unvented Cylinder Water Heater

200 Litre direct unvented cylinder – Electric water heater

200 Litre direct unvented cylinder in highly corrosion resistant duplex stainless steel with 2 x 3kW immersion heaters as standard or the option of 3 x3kW immersion heaters for mains pressure hot water from Flexiheat UK

Looking for a 200 litre direct unvented cylinder or 210 litre direct unvented cylinder in duplex stainless steel ? then we have you covered as we supply a 215 litre direct unvented cylinder which covers these direct models hot water capacity.

Manufactured in the UK, with quality manufacturing processes,our 200 litre direct unvented cylinder full conforms to the “G3” unvented cylinder building regulations , having WRAS, NSF WRC, CE and KIWA independent approvals.

This 200L direct unvented cylinder is a twin immersion cylinder, with 2 x 3kW immersion heaters fitted as standard to this direct unvented hot water cylinder.

Our 200 Litre unvented direct cylinder offers mains pressure hot water powered by electricity directly, rather than using a gas boiler or oil boiler to power the unit like in an indirect unvented cylinder type.

These 200 litre direct unvented cylinders come with a 25 year warranty for the corrosion-resistant duplex stainless cylinder when used in domestic hot water heating applications.

Our 200L unvented direct cylinder will provide a plentiful supply of hot water for your bathroom or showers at mains water pressure.No additional pump is normally required for the hot water system with a direct unvented cylinder.

This competitively priced cylinder is made with quality manufacturing processes in the UK and has high flow rates for cold water mains pressure water heating.

These 215 Litre direct unvented cylinders (which cover 200 or 210 Litres models) are generally suitable for a 3 Bedroom property with 2 Baths/Showers.

No external expansion vessel is required

This 200 litre direct unvented cylinder has a patented internal hot water expansion system which eliminates the need for an external expansion vessel by using a venturi valve to maintain an air pocket within the direct unvented stainless steel cylinder.

This unvented system ensures a long product life and performance for the direct unvented cylinder because it has no moving parts, which reduces installation, running and lifetime costs for this 200 litre direct cylinder made with quality manufacturing standards and processes.

Internal air gap system for our direct unvented hot water cylinders- no external expansion vessel is required as this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance ensuring mains pressure hot water flow throughout the property whatever the heat source feeding the unvented hot water cylinder.

Our internal air gap and venturi valve system used on our direct unvented hot water cylinders- no external expansion vessel is required and little to no maintenance is required for this competitively priced cylinder / unvented hot water system.

Stainless steel direct unvented cylinder – 200 Litre

Our 200 litres direct unvented cylinder is manufactured in stainless steel, duplex stainless steel to be exact. This duplex stainless steel is known for its excellent strength, exceptional resistance to stress corrosion, cracking and pitting, making it suitable for demanding water heating conditions.

Stainless steel tanks or cylinders are also suitable for installing in soft water areas as well as hard water areas. Glass lined mild steel tanks should not be used in naturally soft water areas, as this type of unvented cylinder can experience significant and rapid corrosion to the product.

Technicnal specification – 200 litre direct hot water cylinder (210 &215 Litres as well)

Our 200 litre direct unvented hot water cylinder has the following dimensions (yes our unit is 215 Litres of storage – so also covers the 210 litre direct unvented cylinder requirements)

Dimensions drawing of our direct unvented cylinders in duplex stainless steel - 80 litre to 500 Litre - Flexiheat UK

Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models

 

Our 200 litre hot water cylinder dimensions are as follows 

 

210 litre direct unvented cylinder in stainless steel dimensions, which is a direct pressurised hot water cylinder and a dual or triple 3kW or 6kW immersion cylinder from Flexiheat UK

200 Litre direct unvented cylinder – it’s actual 215 Litres of volume – so covers the 210 direct unvented cylinder requirement as well.

Hot water heat-up time and recovery rates for our direct unvented cylinder, 215 litres in capacity

As standard, our 215 litre direct-pressurised hot water cylinders in high-grade stainless steel are fitted with 2 x 3kW immersion heaters with proven technology and quality.Following are the hot water heat up times.

200 Litre direct unvented cylinder in duplex stainless steel water heating and recovery times from Flexiheat UK

Water heating and recovery times in minutes for our 200 litre unvented direct cylinder with the standard 2 x 3kW immersion heaters.

 

We also do the unit with 3 immersion heaters (3 x 3kW) or can upgrade the power output of these immersions to 6kW each – giving a total kW output possible of 18kW for this size hot water cylinder. This affects the above times accordingly.

The full brochure and installation manuals are here – 

Download the Hot water cylinders direct and indirect unvented brochure from Flexiheat UK

Download the installation & technical manual for our direct and indirect hot water cylinders

Should you require a different volume direct unvented hot water heater, we have a full range from 80 Litres to 500 litres in capacity, which are detailed on this webpage – 80 to 500 Litre direct unvented cylinders.

200 Litre direct cylinder standard components

Our 200 litre direct unvented cylinder models come complete with the following supplied accessories to suit the product –

2 x 3kW Incoloy immersion heaters including control and cut out thermostats as standard with our dual immersion cylinder.

Option of 3 x 3kW immersion heaters – making this 215L direct cylinder a triple immersion heater cylinder – we can actual fit 3 x 6kW immersion heaters to this unit if so required.

22mm Cold water inlet pressure reducing valve /expansion relief in a combination valve for high flow rates

22mm Hot water outlet, again for high flow rates

Our 200L unvented direct cylinders are fitted with a secondary DHW return connection as standard.

Dual thermostat (control thermostat and energy cut out thermostat)

Tundish

Pressure and temperature relief valve mounted to the direct unvented cylinder.

200 litre direct unvented cylinder installation

All direct unvented cylinders must be fitted by a plumber or heating engineer with “G3” unvented qualifications; this certification ensures the necessary knowledge and skills to install and maintain unvented hot water storage systems. In the UK, building control will not issue a building regs certificate unless a qualified person has fitted the unit.

To locate a G3 qualified heating engineer close to you, please consider using this website – gas safe register

Contact Flexiheat UK

For further information or more details, check stock availability, lead time, delivery, prices or to purchase our 200 litre direct unvented cylinder, as we sell direct our competitively priced cylinder, which is made in the United Kingdom from duplex stainless steel with quality manufacturing methods and a manufacturer 25 year warranty (for domestic use). Please contact our sales team on 01202 822221 or use our site email contact form.

300 Litre Direct Unvented Cylinder Water Heater

300 Litre direct unvented cylinder

300 litre direct unvented cylinder in stainless steel, using 100% energy efficient immersion heaters to heat these hot water cylinders to provide water heating for bathroom and showers with a 25 year warranty for domestic use from Flexiheat UK

Our 300 litre direct unvented cylinder is engineered in corrosion-resistant duplex stainless steel and is a competitively priced cylinder. We designed it to achieve high flow rates and a long product life using proven technology and a quality manufacturing process for this unvented hot water cylinder for mains pressure hot water.

When gas is unavailable or when people prefer to use carbon-free electricity sources for water heating, they frequently use electric water heating.

Patented unvented hot water expansion system

The patented internal hot water expansion system, which uses a venturi valve to maintain an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel.

This unvented system has a long product life because it has no moving parts, which reduces running and lifetime costs.

Internal air gap system for our direct unvented hot water cylinders- no external expansion vessel is required as this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance ensuring mains pressure hot water flow throughout the property whatever the heat source feeding the unvented hot water cylinder.

Our internal air gap and venturi valve system used on our direct unvented hot water cylinders- no external expansion vessel is required and little to no maintenance is required for the unvented hot water system.

 

As a result, our 300 Ltr direct unvented cylinder need less space, pipework and plumbing fittings, making the installation simpler and lowering both costs and time required for installation.

What is a 300L direct unvented cylinder suitable for?

A rough guide is that 300 litre direct unvented hot water cylinders are suitable for larger homes, typically a 4-bedroom house with 2 bathrooms/showers or larger, or for properties with a high demand for hot water.

However, people’s hot water usage patterns can vary from household to household. We prefer to give you the hot water usage data, and you decide if it suits your hot water needs.

In the United Kingdom, we are required to keep DHW at 60°C since it eliminates the possibility of Legionella disease and is the minimum recommended storage water temperature for the UK.

If the stored water temperature is 60°C, the amount of required water is in red, to be blended down to 43°C (the maximum bathing temperature before scalding can occur).

Please use 10°C for England and Wales as the lowest cold-water wintertime temperature and use 5°C for Scotland and Northern Ireland.

If the incoming cold-water temperature                                is 10°C                                is 5°C

A bath uses around 135 litres of water at 43°C                    89 litres                               94 litres

A standard 8-litre shower head x 5 minutes                         30 litres                               31 litres

And yes, 5 minutes is the average showering time—say all the time and motion studies report.

A kitchen sink holds up to 20 litres of water                        16 litres                                 16.5 litres

To ensure the removal of grease from dishes and cooking utensils, the standard temperature for washing up water is 50°C.

Toilet sink taps—standard type—are around 4 litres per minute; “spray” type taps are 2 litres per minute and tend to be on for a brief period.

Please see the recovery time data below for our 300 Litre direct unvented cylinder to establish if this the correct 300 litre electric water heater for your circumstances and demands.

This 300 Litre volume direct unvented cylinder is a popular seller in this range, however, should you wish a larger volume cylinder, then please see the following webpage – direct unvented cylinder range

Hot water heat-up time and recovery rates for our direct unvented cylinder, 300 litres in capacity

As standard, our 300 litre direct-pressurised hot water cylinders in high-grade stainless steel are fitted with 2 x 3kW immersion heaters with proven technology and quality.

Our 300 Litre unvented indirect cylinder has the following hot water heat-up time and recovery rates with standard 2 x 3kW immersions fitted:

300 Litre direct unvented cylinder water heating and recovery times Flexiheat UK

Water heating and recovery times in minutes for our 300 litre unvented direct cylinder.

Should you require another size direct unvented hot water cylinder, then we do a full range from 80 to 500 Litres, which are detailed on this webpage – Unvented Direct Cylinder in stainless steel range.

Upgraded immersion heater options 

We have the option of upgrading the immersion heaters to larger outputs for quicker heat recovery on both the 2 and 3 immersion model options.

This 300 litre direct unvented cylinder can also be supplied with 3 x 3 kW immersion electric heaters – giving a total kW output of 9 kW, with a recovery time from 10°C to 65°C of 130 minutes (or 2.17 hours).

We can provide this 300 Ltr direct unvented cylinder with 3 x 6 kW immersion heaters if requested. These heaters can be connected to either a single phase at 240 volts (which needs 32 amps for each heater) or three phases (which needs 10.66 amps for each phase), resulting in a total power of 18 kW. This setup allows the water to heat from cold (10°C) to 65°C in 66 minutes for the 305 litres of water stored.

We also must upgrade the standard temperature and pressure relief valve to a larger output model, as the standard temperature and pressure relief valve is rated to 10kW of output.

All of our unvented hot water cylinders have a pressure test at the factory, and all are tested to 10 bar pressure and have a maximum working pressure of 5.5 bar.

Should you wish to have a larger output of up to 36 kW for a 300 Litre direct water heater, then please see this webpage – Commercial electric water heater range

Unvented Direct Cylinder 300 Litres: Features and Benefits

  • Enhanced Venturi valve technology, which automatically replenishes the internal air gap within the unvented cylinder.
  • Dual immersion cylinder: 2 x 3 kW immersion heaters as standard, with the option of 3 × 3 kW immersion heaters or 3 × 6 kW immersion heaters like so.
Our direct unvented hot water cylinders - having an inbuilt expansion system require no external expansion vessels to be fitted

Our direct unvented hot water cylinders – having an inbuilt expansion system require no external expansion vessels to be fitted – making installation in tight spaces easy

  • 3 bars of water pressure at the outlet (subject to incoming pressure)
  • Direct delivery of hot water under mains pressure allows for high flow rates.
  • No expansion vessel or moving parts, ensuring low maintenance.
  • ErP “C” heat loss rating for reduced energy heat loss and consumption.
  • Benefits from an evolved design and quality manufacturing for improved performance at low flow rates.
  • Our 300 litre direct unvented cylinder comes with a DHW secondary return connection.
  • As standard, it comes with 22mm connections (which will produce 40 Litre per minute), but it is also available with a 28mm-diameter stainless steel inlet and outlet for high flow rates ( 56 Litres per minute).
  • This unvented hot water cylinder has 60mm fire retardant insulation for reduced heat loss.

300 litre unvented direct cylinder dimensions

Our 300 litre stainless steel direct unvented cylinder has the following dimensions:

Dimensions drawing of our direct unvented cylinders in duplex stainless steel - 80 litre to 500 Litre - Flexiheat UK

Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models

The highly corrosion-resistant duplex stainless steel 300 Ltr capacity direct unvented cylinder has the following dimensions in mm:

Direct unvented 300 Litre cylinder in stainless steel dimensions, which is a direct pressurised hot water cylinder and a dual or triple immersion cylinder from Flexiheat UK

The full brochure and installation manuals are here – 

Download the Hot water cylinders direct and indirect unvented brochure from Flexiheat UK

Download the installation & technical manual for our direct and indirect hot water cylinders

Unvented direct cylinder 300 ltr approvals

The 300 ltr direct unvented cylinder we sell has been certified by CE, BBA, and WRAS, which are independent organisations that ensure hot water heating products are safe and meet regulations, and it also has ISO, KIWA, and WRC certifications, showing that our stainless steel cylinders are made with high-quality standards.

Warranty of the 300 Litre hot water cylinder

We’re so sure of the quality of our 300 litre unvented direct cylinder that they come with a 25-year warranty for use in residential locations like homes, apartments, and so on. The warranty covers the stainless steel hot water cylinder for 25 years, while the other parts, like the immersion heaters, control thermostats, and so on, are covered for one year from the date of purchase, subject to conditions.

Contact Flexiheat UK

Please contact us at 01202 822221 to answer any questions or use the company site contact email form to get further information or details, the current stock situation, delivery options, or a cost on the best 300 litre direct unvented cylinder/300Ltr unvented direct cylinder models on the UK market. We manufacture these models from high-grade duplex stainless steel, which comes with a 25-year warranty for domestic use (5 year warranty for commercial use) , a low heat loss rating and WRAS independent approvals.We sell direct to both end users and trade customers.

210 Litre Indirect Unvented Cylinder

210 Litre indirect unvented cylinder

210 Litre indirect unvented cylinder in stainless steel for the delivery of mains pressure hot water heating with no expansion vessel required and reduce heat loss insulation for low water heating losses and with WRAS independent approvals from Flexiheat UK.

Our 210 litre indirect unvented cylinder is the best and most competitively priced cylinder on the UK market, manufactured in stainless steel with proven technology and quality manufacturing for maximum life with the capacity to supply mains pressure hot water for your bathroom, shower, wet rooms, and kitchen tap hot water demands in domestic properties via a domestic hot water sealed system.

Conventional boiler powered

This indirect unvented cylinder is “indirect,” meaning that the cylinder has a coil within the inner cylinder, which needs to be connected and fed by a conventional boiler or traditional boiler, be it an electric boiler, gas or oil boilers.

Being an unvented water storage cylinder, you cannot use solid fuel boilers as the heat source. You must use a vented cylinder for solid fuel boilers, that has a vent pipe to account for the DHW expansion.

Unvented hot water storage tank

Our 210 Litre indirect unvented hot water cylinder does not require an external expansion vessel, as it uses a patented self-sustaining internal air gap within the cylinder to account for the hot water expansion pressure that requires minimum to no maintenance.

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders - Flexiheat UK

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders – Flexiheat UK

What is an unvented indirect cylinder?

A 210 ltr unvented indirect cylinder receives its supply directly from the mains water supply directly, allowing it to produce hot water at a significantly higher pressure than a traditional vented cylinder due to its pressurisation.

An indirect unvented cylinder is a type of hot water cylinder that uses a primary coil to heat water indirectly, providing a safe and efficient hot water supply.

Indirect unvented cylinders are designed to work with a boiler as a heat source, providing a reliable and efficient domestic hot water supply.

What hot water demand is a 210L indirect hot water cylinder suitable for?

The overall amount of hot water used is also greatly influenced by individual behaviours. The amount of hot water used by two houses of the same size might range greatly, with one household needing twice as much as the other.

Understanding peak demands and making sure you have the ideal ratio of cylinder capacity to reheat times are the most important factors.

As a general guideline, use the following average consumption values for hot water requirements per person per day:

• Low Consumption: 20–30 litres

• Average consumption: 30–50 litres.

• High consumption: 50–70 litres

source – hotwater.org.uk

Generally, a 3-bedroom property with multiple bathrooms i.e. 1 or 2 baths or showers should utilise a 210L unvented indirect cylinder.

Although if the household is a high-water user, then you should look at the next volume size up cylinder, our 250 Litre unvented indirect cylinder, which is detailed on this webpage – 250 Litre indirect unvented cylinder.

The product offers key specifications, features, and benefits

  • Made from highly corrosion-resistant duplex stainless steel, these 210L unvented indirect models ensure a long product life and minimal maintenance.
  • Note: no sacrificial anode is required for a stainless-steel unvented cylinder.
  • We manufacture and certify our units in accordance with the BBA, CE, KIWA, ISO, NSF WRC, and WRAS independent approvals.
  • The full benefit of quality manufacturing and proven technologies at a competitive price.
  • We use a stainless-steel indirect heating coil (a heat exchanger) to speed up heat transfer, minimise heat loss, and enable high flow rates. This corrugated coil heat exchanger provides faster reheat times compared to standard plain tube coils.
  • We use 60 mm thermal insulation to reduce heat loss – we use reduced heat loss manufactured factory-injected polyurethane foam insulation bonded onto our highly corrosion-resistant duplex stainless steel tank on our 210-litre cylinder to minimise heat loss and running costs. This high-grade insulation is HCFC/CFC free (ODP=0, GWP=1).
  • Minimal heat loss: Because these units have an ErP rating, they lose less heat, which is better for the environment.
  • It comes standard with a 3 kW immersion heater. This immersion heater is made from Incoloy for long durability that can be used for additional off-peak immersion heating, top-up or emergency water heating should the gas or oil conventional boiler fail.
  • The factory set pressure relief valve ensures a safe and efficient operation of these stainless steel indirect water heaters.
  • Features a secondary return for a DHW recirculation system if required
  • It offers high flow rates for showers and baths in both residential and commercial settings at a maximum inlet pressure of 3.5 bar, eliminating the requirement for a booster pump.

Our 210 litre indirect unvented hot water cylinders are manufactured from duplex stainless steel and thus don’t require a sacrificial anode, which results in less maintenance time and costs for our 210 litre indirect unvented cylinders.

Our indirect unvented cylinder range allows for installation in smaller spaces because it doesn’t require an external expansion vessel. On the left is our indirect unvented cylinder with no expansion vessel installed, and on the right is an indirect cylinder with an external expansion vessel system, which requires a lot more space for the associated pipe work and connections.

Indirect unvented hot water cylinders with internal expansion system for space saving installation Flexiheat UK

On the left – our patented internal air gap system indirect hot water cylinder – on the right – competitor units require an external expansion vessel which requires more space and installation time and copper tube and fittings.

 

Hot water cylinder detail for our 210 Litre unvented indirect cylinder

First we have the dimensions of our indirect unvented cylinder, 210 litres in capacity.

Dimension diagram of our Indirect hot water cylinders in stainless steel with internal expansion system from 80 Litres to 500 Litres from Flexiheat UK

Our indirect hot water heater dimensions diagram

 

Dimension data in “mm” for the above specification diagram

Dimension data table of our 210L unvented indirect cylinders in stainless steel from Flexiheat UK

All dimesions in mm

 

The below heat exchanger coil output (kW) is based on a flow temperature of 85°C. If you require higher outputs, then please see our indirect high recovery cylinder range.

210 Litre unvented indirect hot water cylinder technical data with heat exchanger output and hot water heating recovery rates from Flexiheat UK

 

Download the Indirect and direct hot water cylinders in stainless steel brochure from Flexiheat UK

Download the  Installation and maintenance manual for Flexiheat UK indirect and direct hot water cylinders

 

Standard supplied indirect hot water cylinder unvented components

  • Temperature/Pressure Safety Relief Valve: set at 90°C and 7 bar pressure (factory fitted to the indirect unvented cylinder)
  • The combination (control) valve consists of a line strainer, a non-return (check) valve, a pressure reducing valve, and an expansion relief valve. Supplied loose to be fitted to the incoming cold water mains pipework to reduce the maximum inlet pressure.
  • 3 kW Incoloy (a better material than stainless steel) immersion heater, which is single-phase 240-volt powered, incorporating a control thermostat and resettable safety cut-out with WRAS independent approvals. For backup hot water heating or a cheap tariff electric power.
  • We have the option to upgrade the immersion heater to a 6kW version on this indirect unvented cylinder, which can be powered by either 1 phase or a 3-phase electric power supply.
  • The energy cutout thermostat is set to operate at 82°C (+/-5°C).
  • A motorised valve is designed to cut the heat source plumbing to the cylinders in the event of a high-temperature cutout activation.

Warranty of our indirect unvented cylinder

Because this 210L indirect unvented hot water cylinder is manufactured in duplex high-quality stainless steel, which is highly corrosion resistant.

The hot water cylinder comes with a 25-year guarantee when used in a domestic water heating application (standard household use). Warranties vary if used in a commercial water heating application, then the warranty is reduced to 5 years.

G3 unvented indirect cylinder installation regulations

For England and Wales, our indirect unvented cylinder range is covered by Section G3 of the Building Regulations. For Scotland, it is covered by Technical Standard P3, and for Northern Ireland, it is covered by Building Regulation P5. Compliance can be achieved through a Competent Person Self-Certification Scheme, where a heating engineer with the Unvented G3 Certificate possesses the necessary knowledge and skills to install and maintain unvented hot water storage systems, or by notifying the local authority building control department.

Do not try to install or service an unvented cylinder unless you have the necessary certificate or qualifications. An unvented hot water cylinder can explode if not correctly fitted with all of the safety systems that they require.

Installation and maintenance considerations

Ensure the cylinder is installed by a qualified professional and follow the manufacturer installation requirements, with the tundish positioned for occupant visibility and away from electrical devices.

Regularly check and service the pressure relief valve in line with the manufacturer standards and servicing instructions.

To prevent hot water limescale buildup within the cylinder, especially in hard water areas, consider adding a scale defender.

 

Water hardness map of the UK and Ireland

Water hardness map of the UK and Ireland – a lot of the country is Hard to Very hard in terms of calcium levels, which effects scale potential.

Contact us

For more details, check stock availability, lead time, delivery, price or to purchase our 210 litre indirect unvented cylinder, as we sell direct our competitively priced cylinder, which is made in the United Kingdom from duplex stainless steel with quality manufacturing methods and a manufacturer 25 year warranty (for domestic use). Please contact our sales team on 01202 822221 or use our site email contact form.

400 Litre indirect unvented cylinder

400 Litre indirect unvented cylinder

 

400 Litre indirect unvented cylinder or 400 litre unvented hot water cylinder in stainless steel for the delivery of mains pressure hot water heating with reduce heat loss manufactured insulation for low water heating losses from Flexiheat UK

Our 400 litre indirect unvented cylinder, or calorifier, is manufactured in stainless steel with proven technology and quality manufacturing processes and has the capacity to supply your mains pressure hot water demands for your bathrooms, showers, wet rooms, and hot water taps.

Conventional boiler fed

This indirect unvented cylinder is “indirect,” meaning that the cylinder has a coil within the inner cylinder that is a heat exchanger, which needs to be fed by a conventional boiler, be it electric, gas, or oil.

Being an unvented cylinder, you cannot use solid fuel traditional boiler as the heat source. You must use a vented cylinder for a solid fuel conventional boiler.

Unvented cylinder features of our indirect models

Our 400 Litre unvented indirect cylinder does not require an external expansion vessel, as it uses a patented self-sustaining internal air gap within the cylinder to account for the hot water expansion pressure that requires minimum to no maintenance.

Internal air gap system for our unvented hot water cylinders- no external expansion vessel is required as this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance ensuring mains pressure water flow throughout the property whatever the heat source feeding the unvented hot water cylinder.

Our internal air gap and venturi valve system used on our unvented hot water cylinders- no external expansion vessel is required and little to no maintenance is required for the unvented hot water system.

 

 

Hot water heating performance

A 400l indirect unvented cylinder is suitable for larger domestic properties with 2 or 3 showers/2 baths properties or light commercial water heating applications.

As a general guideline, use the following average consumption values for hot water requirements per person per day:

• Low Consumption = 20–30 litres.

• Average consumption = 30–50 litres.

• High consumption = 50–70 litres.

Hot water heating times and recovery rates specification

The below heat exchanger coil output (kW) is based on a flow temperature of 85°C. If you require higher outputs, then please see our indirect high-recovery cylinder range.

The heat-up times, recovery times, and weights of our 400L indirect hot water cylinder—unvented model.

400 Litre unvented indirect hot water cylinder technical data coil size and heating recovery rates Flexiheat UK

 

Download the –Indirect and direct hot water cylinders in stainless steel brochure from Flexiheat UK

Download the –  Installation and maintenance manual for Flexiheat UK indirect and direct hot water cylinders

Key features and benefits

These 400 Litre indirect cylinders are made from highly corrosion-resistant duplex-grade stainless steel, ensuring a long product life and minimal maintenance (25 year warranty for domestic use and 5 year warranty for commercial use).

No sacrificial anode is required for this stainless steel 400 litre indirect unvented cylinder.

We manufacture and certify our indirect cylinders in accordance with the BBA, CE, KIWA, ISO, NSF WRC, and WRAS independent approvals.

400 Litre indirect cylinders with superb manufacturing standards and proven capable technologies at competitive prices.

We use a stainless steel indirect heating coil (heat exchanger) to speed up heat recovery and enable high hot water flow rates.

We use 60 mm insulation to reduce heat loss on our 400 litre indirect cylinders – we use reduced heat loss manufactured factory-injected polyurethane foam insulation bonded onto our highly corrosion-resistant duplex stainless steel tank on our 400 Litre cylinder to minimise heat loss and running costs. This high-grade insulation is HCFC/CFC-free (ODP=0, GWP=1).

This 400 litre unvented hot water cylinder has an ErP “C” rating; they lose less heat, which is better for the environment.

It comes as complete with a 3kW immersion heater as standard. Incoloy construction provides long durability for this immersion heater.

The unvented kit, including a pressure relief valve, ensures a safe and efficient operation of this 400 Litre stainless steel indirect cylinder range.

We offer this 400 litre unvented indirect cylinder with either the standard 22mm pipework connections or larger 28mm for high flow rates for showers and baths in both residential and commercial settings.

Smaller space required and easier installation for our 400 litre unvented cylinder

Our 400 litre unvented indirect cylinder allows for installation in smaller spaces because it doesn’t require an external expansion vessel. On the left is our indirect unvented cylinder with no vessel installed, and on the right is an indirect cylinder with an external expansion vessel system, which requires a lot more space for the associated pipework, components and materials.

Indirect unvented hot water cylinders with internal expansion system for space saving installation Flexiheat UK

On the left – our patented internal air gap system indirect hot water cylinder – on the right – competitor units require an external expansion vessel which requires more space and installation time and tube and fittings.

400 litre unvented cylinder dimensions 

Dimensions of our indirect unvented cylinder 400 Litres in capacity.

 

Dimension diagram of our Indirect hot water cylinders in stainless steel with internal expansion system from 80 Litres to 500 Litres from Flexiheat UK

Our indirect hot water heater dimensions diagram

Dimension data in mm for the above specification diagram.

 

Dimension data table of our 400L unvented indirect cylinders in stainless steel from Flexiheat UK

 

Immersion heater for top-up or backup DHW heating

Should the electric, gas, or oil conventional boiler fail, this 400 litre unvented cylinder has an immersion heater fitted to these indirect cylinders that allows for backup or additional hot water heating via electric power, just like direct models. Direct water heating models just use immersion heaters for the water heating of the unit.

Heat pump use?

This 400 litre unvented indirect cylinder range is designed to work with a conventional boiler, be it oil, electric or gas boilers, and have a heat exchanger suited to the higher hot water temperatures that these boilers can produce. With lower temperatures that heat pumps can produce, they require a larger heating coil to get the maximum heat transfer in indirect models, and is the same for solar thermal systems. We do a specific range for this application, which is listed here: hot water cylinders for heat pump systems

Contact us

For more details, check stock, lead time, delivery, cost, or purchase our 400 litre indirect unvented cylinder, which is one of the best and most competitively priced 400 Litre indirect cylinders on the UK market. They are manufactured in the United Kingdom from duplex stainless steel with quality manufacturing methods and a manufacturer 25 year warranty (for domestic use, 5 years warranty for commercial applications). Please contact our sales team on 01202 822221 or use our site email contact form.

150 Litre Indirect Unvented Cylinder

150 Litre indirect unvented cylinder

150 Litre indirect unvented cylinder in stainless steel for the delivery of mains pressure hot water heating with no expansion vessel required and reduce heat loss manufactured insulation for low water heating losses and with WRAS independent approvals from Flexiheat UK

150 litre unvented indirect cylinder in duplex stainless steel from Flexiheat UK.

Our 150 litre indirect unvented cylinder is the best and competitively priced cylinder on the UK market, manufactured in duplex stainless steel with proven technology and quality manufacturing with the capacity to supply mains pressure hot water for your bathroom, shower, wet rooms, and kitchen tap hot water demands in domestic properties via a domestic hot water sealed system.

This indirect unvented cylinder is “indirect”, meaning that the cylinder has a coil within the inner cylinder, which needs to be connected and fed by electric, gas, or oil boilers. Being an unvented cylinder, you cannot use solid fuel boilers as the heat source. You must use a vented cylinder for solid fuel.

Unvented indirect cylinder 150 litre

Our 150 Litre indirect unvented hot water cylinder does not require an external expansion vessel, as it uses a patented self-sustaining internal air gap within the cylinder to account for the hot water expansion pressure that requires minimum to no maintenance.

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders - Flexiheat UK

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders – Flexiheat UK

What is an unvented indirect cylinder?

An unvented hot water cylinder receives its supply directly from the main water system, allowing it to produce hot water at a significantly higher pressure than a traditional vented cylinder due to its pressurisation.

Mains pressure hot water cylinders available in direct and indirect configurations.

An indirect unvented cylinder is a type of hot water cylinder that uses a primary coil to heat water indirectly, providing a safe and efficient hot water supply.

Indirect unvented cylinders are designed to work with a boiler as a heat source, providing a reliable and efficient domestic hot water supply.

What hot water demands is a 150L indirect hot water cylinder suitable for?

The overall amount of hot water used is also greatly influenced by individual behaviours. The amount of hot water used by two houses of the same size might range greatly, with one household needing twice as much as the other.

Understanding peak demands and making sure you have the ideal ratio of cylinder capacity to reheat times are the most important factors.

As a general guideline, use the following average consumption values for hot water requirements per person per day:

• Low consumption: 20–30 litres

• Average consumption: 30–50 litres.

• High consumption: 50–70 litres

Source- hotwater.org.uk

As a good rule of thumb, a 1 bedroom with 1 bathroom or a 2 bedrooms (with average water consumption) 1 bathroom property should use a 150 litre indirect unvented cylinder.

Although if the household is a high-water user, then you should look at the next size up cylinder, our 175 Litre or even our 215 Litre unvented indirect cylinder, which are detailed on this webpage – indirect unvented cylinders range

Features,specification and key benefits of our 150 litre unvented indirect hot water cylinder

  • These 150L unvented indirect models are made from highly corrosion-resistant duplex stainless, ensuring a long product life and minimal maintenance.
  • Note—No sacrificial anode is required for a stainless steel unvented cylinder.
  • Our 150 litre unvented indirect hot water cylinder is certified in accordance with the following approvals: BBA, CE, KIWA, ISO, NSF WRC, and WRAS independent approvals.
  • Quality manufacturing and proven technologies at a competitive price.
  • We use a stainless-steel indirect heating coil (a heat exchanger) to speed up heat transfer, minimise heat loss, and enabling high flow rates. This corrugated coil heat exchanger provides faster reheat times compared to a standard coil indirect unvented cylinder.
  • We use 60mm thermal insulation to reduce heat loss—we use reduced heat loss factory-injected polyurethane foam insulation bonded onto our highly corrosion-resistant stainless steel tank on our 150 Litre cylinder to minimise heat loss and running costs. This high-grade insulation is HCFC/CFC-free (ODP=0, GWP=1).
  • Minimal heat loss: Because these units have an ErP rating, they lose less heat, which is better for the environment
  • It comes standard with a 3kW immersion heater. This immersion heater is made from Incoloy for long durability that can be used for additional off-peak immersion heating, or top-up, or emergency water heating should the gas or oil conventional boiler fail.We can upgrade the 3kW immersion heater to a 6kW immersion heater if required.
  • The pressure relief valve ensures safe and efficient operation of these stainless steel indirect water heaters.
  • It ensures high flow rates for showers and baths in both residential and commercial settings at a maximum inlet pressure of 3.5 bar, eliminating the requirement for a booster pump.

Our 150 litre indirect unvented hot water cylinders are manufactured from duplex (the best) stainless steel and thus don’t require a sacrificial anode, which results in less maintenance time and costs for our 150 litre indirect unvented cylinders.

Our indirect unvented cylinder range allows for installation in smaller spaces because it doesn’t require an external expansion vessel. On the left is our indirect unvented cylinder, and on the right is an indirect cylinder with an external expansion vessel system, which requires a lot more space for the associated pipework and plumbing connections.

Indirect unvented hot water cylinders with internal expansion system for space saving installation Flexiheat UK

On the left – our patented internal air gap system indirect hot water cylinder – on the right – competitors similar products require an external expansion vessel which requires more space and installation time and tube and fittings.

 

Hot water cylinder detail for our 150 Litre unvented indirect cylinder

First we have the basic dimensions of our indirect unvented cylinder 150 Litres in capacity.

Dimension diagram of our Indirect hot water cylinders in stainless steel with internal expansion system from 80 Litres to 500 Litres from Flexiheat UK

Our indirect hot water heater dimensions diagram

 

Dimensions of our indirect unvented cylinder: 150 liters in capacity.

Dimension data of our 150 Litre unvented indirect cylinder in stainless steel from Flexiheat UK

Heat up times, recovery times, and weights of our 150 Litre indirect hot water cylinder—unvented model.

150 Litre unvented indirect hot water cylinder technical data coil size and heating time and recovery rates from Flexiheat UK

The above heat exchanger coil output (kW) is based on a flow temperature of 85°C. If you require higher outputs, then please see our indirect high recovery cylinder range.

Download theIndirect and direct hot water cylinders in stainless steel brochure from Flexiheat UK

Download the –  Installation and maintenance manual for Flexiheat UK indirect and direct hot water cylinders

Standard indirect hot water cylinder unvented components

  • Temperature/Pressure Safety Relief Valve: set at 90°C and 7 bar pressure (factory fitted to the indirect unvented cylinder)
  • The combination (control) valve consists of a line strainer, a non-return (check) valve, a pressure reducing valve, and an expansion relief valve. Supplied loose to be fitted to the incoming cold water mains pipework to reduce the maximum inlet pressure to 3.5 bar.
  • 3kW immersion heater in Incoloy (a better material than stainless steel) , which is single-phase 240 Volt powered, incorporating a control thermostat and re-settable safety cut-out. For back up hot water heating or a cheap economy electric power system.
  • We have the option to upgrade the immersion heater to a 6kW version on this indirect unvented cylinder, which can be powered by either 1 phase or a 3-phase electric power supply.
  • The energy cut out thermostat is set to operate at 82°C (+/-5°C).
  • Motorised valve to cut the heat source plumbing to the cylinders in the event of a high temperature cut out activation of the control thermostat.

Warranty of our indirect unvented cylinder

Because this 150L indirect unvented hot water cylinder is made from high-quality duplex stainless steel, which is highly corrosion resistant.

The hot water cylinder comes with a 25-year guarantee when used in a domestic water heating application (standard household use). If used in a commercial water heating application, then the warranty is reduced to 5 years.

G3 unvented indirect cylinder install regulations

For England and Wales, our indirect unvented cylinder range is covered by Section G3 of the Building Regulations. For Scotland, it is covered by Technical Standard P3, and for Northern Ireland, it is covered by Building Regulation P5. Compliance can be achieved through a Competent Person Self-Certification Scheme, where a heating engineer with the Unvented G3 Certificate possesses the necessary knowledge and skills to install and maintain unvented hot water storage systems, or by notifying the local authority building control department.

Do not try to install or service an unvented cylinder unless you have the necessary certificate or qualifications. An unvented hot water cylinder can explode if not correctly fitted with all of the safety systems that they require.

Installation and maintenance considerations

Ensure the 150 litre indirect unvented cylinder is installed by a qualified professional and follow the manufacturer requirements, with the tundish positioned for occupant visibility and away from electrical devices.

Regularly check the pressure relief valve in line with the servicing instructions.

To prevent hot limescale buildup within the cylinder, especially in hard water areas, consider adding a scale defender to the cold water mains delivery pipe.

Water hardness map of the UK and Ireland

Water hardness map of the UK and Ireland – a lot of the country is Hard to Very hard in terms of calcium levels, which effects scale potential.

 

 

Contact us

For more details, check stock, lead time, delivery, price, or to purchase our 150 litre indirect unvented cylinder, as we sell direct our competitively priced cylinder, which is made in the United Kingdom from duplex stainless steel with a manufacturer 25 year warranty (for domestic use). Please contact our sales team at 01202 822221 or use our site email contact form.

Pressurised Hot Water Cylinders

Pressurised hot water cylinders – what are they?

Pressurised hot water cylinders, also known as unvented cylinders, are storage tanks that supply pressurised hot water to homes without relying on gravity. These systems are connected directly to the mains water supply; thus, they are a pressurised system, which allows them to provide hot water at high pressure for all taps, sinks, showers, and bath outlets in the house. A steady supply of mains pressure hot water for your property with a hot water storage cylinder.

They are the most popular hot water cylinders on the UK market, with stainless steel unvented hot water cylinders being the most prevalent due to the higher pressures that they can take over copper-manufactured cylinders.

Key Features of Unvented Hot Water Cylinders

  1. Direct Mains Connection: Unlike traditional gravity-fed systems, pressurised cylinders are fed directly from the cold mains water supply.
  2. High Pressure: By storing the water at a high pressure, typically between two and three bar, it enables strong water flow even to outlets at higher elevations.
  3. Heating Methods: These cylinders can be heated either directly using electricity (immersion heaters) or indirectly using an external heat source like a central heating system boiler, heat pumps, or solar system.
  4. Space-Saving: They eliminate the need for a separate cold water storage tank, reducing pipework and freeing up space in the home.

Advantages of an unvented cylinder

  • Delivers high-pressure hot water throughout the home.
  • Can be placed at lower levels in the water supply system.
  • Reduces overall pipework.
  • A pressurised unvented cylinder is ideal for properties with limited space.

How do unvented cylinders differ from traditional gravity-fed hot water cylinders?

Unvented cylinders, also known as pressurised hot water cylinders, differ significantly from traditional gravity-fed tanks in several key aspects:

Water Supply: Unvented cylinders are fed directly from the cold mains water supply, eliminating the need for a separate cold water storage tank in the loft. This direct connection allows for higher pressure and better flow rates throughout the home.

Pressure: Unlike gravity-fed systems, unvented cylinders operate at mains pressure, typically between two to three bar. This results in stronger water flow, especially to outlets at higher elevations.

Space Efficiency: By removing the need for a cold water tank in the loft, unvented hot water storage cylinders save space and reduce overall pipework in the home.

Installation Flexibility: Unvented cylinders don’t rely on gravity to deliver hot water, so they can be installed almost anywhere in the property, not just below the cold water tank.

Water Quality: The sealed nature of unvented systems reduces the risk of water contamination compared to open-vented hot water cylinders.

Expansion Management: Instead of using a vent pipe to handle water expansion during heating, unvented cylinders employ either an expansion vessel or an internal air gap within the hot water cylinders.

Performance: Unvented systems generally provide more consistent pressure and flow rates, especially beneficial in homes with multiple bathrooms or when several outlets are used simultaneously.

Noise: Unvented systems tend to operate more quietly as there’s no need for a cold water tank to refill after use of the hot water heater.

These differences make unvented cylinders a popular choice for modern homes, especially when space is limited or high-pressure/main- pressure hot water is desired throughout the property.

There are two main types of unvented hot water cylinders available:

There are two main types of unvented hot water cylinders available:

Indirect Unvented Cylinders:

These cylinders are designed to work with external heat sources, such as gas or oil boilers (which are a system boiler) or heat pumps. They contain an internal coil through which hot water from the boiler or heat pumps circulates, indirectly heating the water stored in the cylinder. Indirect cylinders usually also include an immersion heater as a backup.

We go into full depth of this range here- indirect unvented cylinders

These indirect duplex stainless steel unvented hot water storage cylinders come with a 25-year warranty for domestic property use.

Direct Unvented Cylinders:

These direct cylinders have built-in electric immersion heaters that heat the water directly within the tank. They are suitable for homes without a boiler or as a standalone hot water solution. Direct cylinders typically have dual electric immersions for efficient heating.

We go into the full depth of this range here- direct unvented cylinders

Again these direct duplex stainless steel unvented hot water storage cylinders come with a 25-year warranty for domestic property use.

When choosing between direct and indirect unvented cylinders, the primary consideration is the existing heating system in the home. Homes with central heating systems with gas or oil boilers, heat pumps or solar thermal heat sources typically use indirect cylinders, while those relying solely on electricity for water heating would opt for direct cylinders.

What safety features are essential for unvented hot water cylinders?

Unvented cylinders, also known as pressurised hot water tanks, require several essential safety features to ensure their safe operation:

  1. Temperature and pressure relief valve: This valve releases excess pressure if it builds up beyond safe levels or releases hot water if the temperature exceeds safe limits, preventing potential explosions.
  2. Expansion Vessel: This component absorbs excess pressure within the system, helping to maintain safe operating conditions.
  3. Thermostat: Controls the water temperature and prevents overheating.
  4. Cut-out Switch: Acts as a safety feature to prevent overheating by shutting off the heating element if temperatures become too high.
  5. Tundish: A visible device that allows for safe discharge of water from the relief valve into the environments, providing a clear indication of valve operation.

These safety devices work together to manage pressure, temperature, and expansion within the unvented cylinder system. It’s crucial to note that these safety features must be installed by a G3-qualified heating engineer and require annual inspection and maintenance to ensure they function correctly. Regular servicing is not only important for safety but also validates the manufacturer’s warranty and ensures compliance with “G3” UK building regulations.

What are the disadvantages of an unvented hot water system?

While unvented cylinders offer many advantages, they also come with several potential drawbacks:

Higher Installation Costs: Unvented systems are typically more expensive to install due to their complex nature and the need for additional safety features.

Specialised Installation: Only G3-qualified heating engineers can install a pressurised hot water tank system. 

Regular Maintenance: Unvented cylinders require annual maintenance checks to ensure safety and compliance with regulations, adding to long-term costs.

Mains Dependency: You won’t have hot water if there’s a mains water supply interruption.

Compatibility Concerns: Some unvented systems may not be compatible with certain types of showers or mixer taps.

Space Requirements: While unvented hot water cylinders eliminate the need for a cold water tank, some unvented cylinders still require space for an expansion vessel, but units with internal expansion systems don’t.

Potential for System Failure: If safety features like pressure relief valves or expansion vessels malfunction, it could lead to more serious issues.

These drawbacks highlight the importance of careful consideration and professional advice when choosing between vented and unvented hot water systems for your property.

Pressurised domestic hot water systems

Pressurised hot water cylinders or unvented hot water cylinders are popular due to the energy-efficient benefits and exploitation of mains pressure water. They can be indirect or direct models to suit the customers’ requirements.

Industrial gas water heaters

Industrial gas water heaters

Industrial gas water heaters in natural gas or LPG propane from Flexiheat UK

150kW or 200kW gas fired industrial water heaters – up to 400kW in cascade from Flexiheat UK

Our industrial gas water heaters are condensing water heaters for maximum energy efficiency and lower hot water heating bills. This industrial gas fired water heater can be used in an industrial instant hot water heater configuration but also can be linked up to a hot water storage tank for water heating applications that require a storage water heater to cover peak or intermittent high demand volumes of hot water.

These gas water heaters are available in either natural gas or LPG/propane-fired hot water systems.

Many applications rely on them for a continuous supply of hot water, thus the term continuous flow water heaters or can be used in stored hot water systems. They possess hot water temperature control capabilities and aim to reduce heat loss for optimal efficiency. Industrial gas fired water heaters are ideal for any office buildings, healthcare facilities, manufacturing processes or settings, and more that require energy efficient industrial water heating solutions.

Industrial gas condensing water heaters

All of our industrial gas fired water heaters are condensing water heaters, with patented advanced burner technologies that ensure reduced energy consumption when producing domestic hot water.

Whether it be to provide hot water for commercial and industrial applications, our ErP-compliant condensing gas water heaters can be used in an instant hot water mode or can be used with a stored hot water tank (storage tank) to ensure that peak water heating demands can be covered.

Either way, we have a full range of water heating solutions for any industrial water heating system requirements you may have.

Industrial tankless gas water heaters

Our industrial tankless water heaters are available in either natural gas fired water heaters or LPG propane gas fired water heaters and are designated the “SFKG” range.

Being condensing water heaters, our industrial instant hot water heaters are a cost effective option when compared to a storage water heater, as they only produce hot water on demand.

Water heater product range and features

A picture of our Industrial tankless hot water heater, gas fired, showing the multiply heat exchangers for redundancy and to ensure reliable domestic hot water heating from Flexiheat UK

SFKG – our Industrial on demand hot water heater range in 150kW or 200kW single units – 400kW in casacde.

 

This full range of industrial gas condensing water heaters has the following benefits:

  • Currently, there are 150 kW or 200 kW industrial condensing water heaters models available, which can cascade up to two units, resulting in a total output of 400 kW. Larger capacity outputs are in the pipeline.
  • The casing houses either three (150 kW model) or four (200 kW model) load-balanced 50 kW stainless steel heat exchangers, ensuring even wear and standard integrated redundancy.
  • A high-efficiency pre-mix gas burner provides a large modulation range; the 150 kW model has a 30:1 modulation range, and the 200 kW model has a 40:1 modulation range for better load matching of the hot water systems demand.
  • Low NOₓ emissions resulting in lower greenhouse gas emissions.
  • The heat exchangers are independent of each other, which guarantees the running of the gas water heater even in case of a single exchanger’s failure. The large 28 mm diameter of the stainless steel exchangers ensures maximum heat transfer and high efficiency (up to 112%) with optimal performance with low water pressure drops.
  • Electronic ignition.
  • Operating temperatures up to 85°C.
  • Easy installation with a compact design, which is basically “plug and play”.
  • Flueing options for single or cascaded units, i.e the exhaust gas flue system.

150 kW industrial tankless water heater, gas-fired—hot water heating performance flow rate data at various Delta T

Water heating performance is directly related to the operating temperatures required, i.e., the temperature rise shown as “Δt,” which is Delta T.

Water Temperature Rise Δt 20 Δt 25 Δt 30 Δt 35 Δt 40 Δt 50 Δt 60 Δt 75 Flow rate
SFKG 150 110.19 88.15 73.46 62.96 55.09 44.08 36.73 29.38 Litres/minute
6,611 5,289 4,408 3,778 3,306 2,645 2,204 1,763 Litres/hour

This 150kW industrial and commercial on-demand gas water heater delivers exceptional instant hot water performance. A standard shower head has a flow rate of 7 litres per minute. In the winter, the temperature of the cold water mains is 10°C for the majority of the UK, while the showering temperature is 40°C, resulting in a temperature rise of 30°C required. This 150 kW industrial instantaneous hot water heater will supply 10 showers with continuous flow hot water if you have the water flow rate and gas supply required.

200 kW industrial tankless water heater, gas-fired—hot water performance flow rate data at various Delta T

Water heating performance is directly related to the operating temperatures required, i.e., the temperature rise shown as “Δt,” which is delta T.

Water Temperature Rise Δt 20 Δt 25 Δt 30 Δt 35 Δt 40 Δt 50 Δt 60 Δt 75 Flow rate
SFKG 200 146.92 117.53 97.94 83.95 73.46 58.77 48.97 39.18 Litres/minute
8,815 7,052 5,877 5,037 4,408 3,526 2,938 2,351 Litres/hour

With a delta T of 30°C, this 200 kW industrial tankless gas water heater will supply 14 showers with continuous flow hot water, as long as you have the water flow rate and gas supply required.

Download the SFKG 150 and 200kW Gas fired industrial and commercial water heaters manual

Gas industrial storage water heater option

Certain industrial water heating solutions necessitate the frequent storage of hot water to meet peak demand.Our water heating solution for this is to couple up our industrial water heaters with a domestic hot water storage tank.

 

Industrial gas fired tankless water heater in conjunction with a domestic hot water storage tank in natural gas or propane LPG gas from Flexiheat UK

Our industrial gas fired tankless water heater range used in conjunction with a DHW storage tank for peak or high domestic hot water demands.

 

Flueing options

These gas fired water heaters for industrial applications, due to the vertical stack modular design, share a common flue pipe, so there’s only one flue required for each water module. As each heat exchanger with the water heater has a flue non-return valve, each heat exchanger within the water heater’s casing can be isolated and serviced while the rest of the heat exchangers continue to work.

No downtime while servicing

This is important, as there will be no downtime for your industrial hot water systems servicing requirements.

Commercial water heaters or industrial water heaters?

Commercial water heaters generally start at 70 kW and above because the gas safe regulations classify gas pipework greater than 35 mm (1 1/4″) in diameter as commercial gas applications. Ultimately, as such, there’s no hard figure in kW for gas fired commercial water heaters, and when they change into industrial gas fired water heaters. Since the 2022 Building Regulations Part L amendments, water heaters used in commercial and industrial applications must comply with condensing gas water heater regulations—for more information, read more here – Condensing Water Heaters Legislation UK

Ensure proper installation by using a suitably qualified commercial gas safe engineer.

Contact us for your industrial gas water heating requirements

For more details, check stock, lead time, delivery, price, or to order our reliable and high-quality industrial gas water heaters, as we sell our high-performance and competitively priced products directly. Please call our sales service team at 01202 822221 or use our site email contact form.

500 Litre indirect unvented cylinder

500 Litre indirect unvented cylinder

500 Litre indirect unvented cylinder in stainless steel for the delivery of mains pressure hot water heating with no expansion vessel required and reduce heat loss insulation for low water heating losses from Flexiheat UK

Our 500 litre indirect unvented cylinder or calorifier options are some of the best and competitively priced cylinders on the UK market, manufactured in stainless steel (or the option of glass lined) with proven technology and quality manufacturing with the capacity to supply mains pressure hot water for your bathroom, shower, wet rooms, and kitchen tap hot water demands.

This indirect unvented cylinder is “indirect,” meaning that the cylinder has a coil within the inner cylinder that is a heat exchanger, which needs to be fed by a traditional boiler, be it electric, gas or oil. Being an unvented cylinder, you cannot use solid fuel boilers as the heat source. You must use a vented cylinder for solid fuel.

Our 500 Litre indirect unvented cylinder does not require an external expansion vessel, as it uses a patented self-sustaining internal air gap within the cylinder to account for the hot water expansion pressure that requires minimum to no maintenance.

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders - Flexiheat UK

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders – Flexiheat UK

 

What is an unvented indirect cylinder?

An unvented hot water cylinder receives its supply directly from the main water system, allowing it to produce domestic hot water at a significantly higher pressure than a traditional vented cylinder due to its pressurisation.

An indirect unvented cylinder is a type of hot water cylinder that uses a primary coil to quickly heat water indirectly, providing a safe and efficient hot water supply.

Indirect unvented cylinders are designed to work with a boiler as a heat source, providing a reliable and efficient domestic hot water supply.

What hot water demand is a 500 litre indirect hot water cylinder suitable for?

The overall amount of hot water used is also greatly influenced by individual behaviours. The amount of hot water used by two houses of the same size might range greatly, with one household needing twice as much as the other.

Understanding peak demands and making sure you have the ideal ratio of cylinder capacity to reheat times are the most important factors.

As a general guideline, use the following average consumption values for hot water requirements per person per day:

• Low Consumption = 20–30 litres

• Average consumption = 30–50 litres.

• High consumption: 50–70 litres

source – hotwater.org.uk

Key features and benefits

  • The cylinder is made from highly corrosion-resistant duplex stainless, ensuring a long product life and minimal maintenance.
  • Note—No sacrificial anode is required for this stainless steel 500 litre indirect unvented cylinder.
  • • We manufacture and certify our units in accordance with the BBA, CE, KIWA, ISO, NSF, WRC, and WRAS independent approvals.
  • Quality manufacturing and proven technologies at a competitive price.• We use a stainless steel indirect heating coil (heat exchanger) to speed up the heat recovery time, minimise heat loss, and enable high flow rates.
  • We use 60mm insulation to reduce heat loss and increase energy efficiency —we use reduced heat loss factory-injected polyurethane foam insulation bonded onto our highly corrosion resistant duplex stainless steel tank on our 500 litre indirect unvented cylinder to minimise heat loss and improve energy efficiency. This high-grade insulation is HCFC/CFC-free (ODP=0, GWP=1).
  • Minimal heat loss: Because these units have an ErP rating, they lose less heat, which is better for the environment.
  • Outer casing – P200 Plastisol
  • It comes standard with a 3kW immersion heater. Our immersion heaters are made from Incoloy for long durability.
  • The pressure relief valve ensures a safe and efficient operation of these stainless steel indirect water heaters.
  • It offers high flow rates for showers and baths in both residential and commercial settings at a maximum inlet pressure of 3.5 to 6 bar, eliminating the requirement for a booster pump.

Our 500 litre indirect unvented hot water cylinders are made from duplex stainless steel and thus don’t require a sacrificial anode, which results in less maintenance time and costs for our 500 litre indirect unvented cylinders.

Our indirect unvented cylinder range allows for installation in smaller spaces because it doesn’t require an external expansion vessel. On the left is our indirect unvented cylinder with no expansion vessel installed, and on the right is an indirect cylinder with an external expansion vessel system, which requires a lot more space for the associated pipework and connections.

Indirect unvented hot water cylinders with internal expansion system for space saving installation Flexiheat UK

On the left – our patented internal air gap system indirect hot water cylinder – on the right – competitor units require an external expansion vessel which requires more space and installation time and tube and fittings.

Hot water cylinder detail for our 500 Litre unvented indirect cylinder

First, we have the basic dimensions of our indirect, unvented cylinder, which has 500 litres of capacity.

Dimension diagram of our Indirect hot water cylinders in stainless steel with internal expansion system from 80 Litres to 500 Litres from Flexiheat UK

Our 500 litre indirect hot water heater dimensions diagram

 

Dimension table and heat exchanger rating detail

Dimension data of our 500 Litre unvented indirect cylinder in stainless steel from Flexiheat UK

Heat-up times, recovery times, and weights of our 500L indirect hot water cylinder—unvented model.

500 Litre unvented indirect hot water cylinder technical data heating coil kW and water heating recovery rates Flexiheat UK

 

Note – Heating coil performance (27kW) is based on a flow temperature of 85C to the coil, water heating performance is reduced with lower flow temperatures to the heat exchanger.

If you require higher outputs, then please see our indirect high-recovery cylinder range.

Download the –

Indirect and direct hot water cylinders in stainless steel brochure from Flexiheat UK

Download the installation manual for full details –

Installation and maintenance manual for Flexiheat UK indirect and direct hot water cylinders

Hi flow rate 500L indirect unvented cylinder option

We can also supply a 500 litre indirect unvented cylinder for higher flow rates for larger domestic and commercial water heating demands; this option benefits from 28mm pipe connections and a 28mm venturi valve rather than the standard 22mm pipe connections and 22mm venturi.

Standard indirect hot water cylinder unvented kit components supplied

  • Temperature/Pressure Safety Relief Valve: set at 90°C and 7 bar pressure (factory fitted to the indirect unvented cylinder)
  • The combination (control) valve consists of a line strainer, a non-return (check) valve, a pressure reducing valve, and an expansion relief valve. Supplied loose to be fitted to the incoming cold water mains pipework to reduce the maximum inlet pressure to between 3.5 to 6 bar to the cylinder.
  • 3kW Incoloy (a better material than stainless steel) immersion heater, which is single-phase 240 Volt powered, incorporating a control thermostat and re-settable safety cut-out with WRAS independent approvals. For backup hot water heating or a cheap economy electric power system.
  • We have the option to upgrade the immersion heater to a 6kW version on this indirect unvented cylinder, which can be powered by either 1 phase or a 3-phase electric power supply.
  • The high limit stat (thermostat) is set to operate at 82°C (+/-5°C).
  • Motorised valve to cut the heat source plumbing to the cylinders in the event of a high-temperature cutout activation.

Warranty of our indirect unvented cylinder

Because this 500L indirect unvented hot water cylinder is made of high-quality duplex stainless steel, which is highly corrosion resistant.

This 500 Litre unvented indirect cylinder comes with a 25-year guarantee when used in a domestic water heating application,with 1 year for the ancillary components (standard household use and subject to manufacturers T&Cs). If used in a commercial water heating application, then the warranty is reduced to five years.

Heat pump hot water cylinder option

500 Litre indirect hot water cylinders for heat pump water heating applications, require a larger heat exchanger. We do a dedicated range of heat pump cylinders with a larger coil here – Hot water cylinders for heat pumps

G3 unvented indirect cylinder installation regulations

For England and Wales, our indirect unvented cylinder range is covered by Section G3 of the Building Regulations. For Scotland, it is covered by Technical Standard P3, and for Northern Ireland, it is covered by Building Regulation P5. Compliance can be achieved through a Competent Person Self Certification Scheme, where a heating engineer with the Unvented G3 Certificate possesses the necessary knowledge and skills to install and maintain unvented hot water storage systems, or by notifying the local authority building control department of the installation.

Do not try to install or service an unvented cylinder unless you have the necessary certificate or qualifications. An unvented hot water cylinder can explode if not correctly fitted with all of the safety systems that they require.

Installation and maintenance considerations

Ensure the cylinder is installed by a qualified professional and follow the manufacturer’s installation requirements, with the tundish positioned for occupant visibility and away from electrical devices.

Regularly check and service the pressure relief valve in line with the servicing instructions.

To prevent hot water limescale buildup within the cylinder, especially in a hard water location ( see the following map), consider adding a scale defender.

Water hardness map of the UK and Ireland

Water hardness map of the United Kingdom and Ireland – a lot of the country is Hard to Very hard in terms of calcium levels, which effects scale potential.

Contact us

For further information, check stock availability, standard delivery or express delivery options, delivery charge, price, or purchase our 500 litre indirect unvented cylinder, as we sell direct to trade customers and individuals our competitively priced cylinder, which is designed and made in the United Kingdom from duplex stainless steel with quality manufacturing methods and a manufacturer 25 year warranty (for domestic use). Please contact our sales team at 01202 822221 or use our site email contact form.

120 Litre Direct Unvented Cylinder

120 Litre direct unvented cylinder

120 Litre direct unvented cylinder in highly corrosion resistant duplex stainless steel with 2 x 3kW immersion heaters for mains pressure hot water

120 Litre direct unvented cylinders in corrosion resistant duplex stainless steel from Flexiheat UK

 

Our 120 litre direct unvented cylinder is engineered in corrosion-resistant duplex stainless steel and is a competitively priced cylinder. We designed it to achieve high flow rates and a long product life using proven technology and a quality manufacturing process for this unvented hot water cylinder for mains pressure hot water.

We’re so sure of the quality of our 120 litre unvented direct cylinder that they come with a 25-year warranty for use in residential locations like homes, apartments, and so on. The warranty covers the stainless steel hot water cylinder for 25 years, while the other parts, like the immersion heaters, control thermostats, and so on, are covered for one year from the date of purchase, subject to conditions.

What is a 120L direct unvented cylinder suitable for?

A rough guide is that 120 litre direct unvented hot water cylinders suit flats or smaller homes with one or two bedrooms and a bathroom with one bath and/or shower.

However, people’s hot water usage patterns can vary from household to household. We prefer to give you the hot water usage data, and you, our customer, decide if it suits your hot water needs.

In the United Kingdom, we are required to keep DHW at 60°C since it eliminates the possibility of Legionella disease and is the minimum recommended water temperature.

If the stored water temperature is 60°C, the amount of required water is in red, to be blended down to 43°C (the maximum bathing temperature before scalding can occur).

Please use 10°C for England and Wales as the lowest cold-water wintertime temperature and use 5°C for Scotland and Northern Ireland.

If the incoming cold-water temperature                                            is 10°C                                   is 5°C

A bath uses around 135 litres of water at 43°C                                 89 litres                                 94 litres

A standard 8-litre shower head x 5 minutes                                     30 litres                                 31 litres

And yes, 5 minutes is the average showering time—say all the time and motion studies report.

A kitchen sink holds up to 20 litres of water                                    16 litres                                   16.5 litres

To ensure the removal of grease from dishes and cooking utensils, the standard temperature for washing up water is 50°C.

Toilet sink taps—standard type—are around 4 litres per minute; “spray” type taps are 2 litres per minute and tend to be on for a brief period.

Please see the recovery time data below for our 120L direct cylinder to establish if this is the right 120L electric water heater for your circumstances and demands.

This 120 Litre volume direct unvented cylinder is the second most popular seller in this range, however, should you wish a larger volume cylinder, which is  our most popular direct unvented cylinder that we sell, then please see the following webpage – 150 Litre direct unvented cylinder

Hot water heat-up time and recovery rates for our direct unvented cylinder, 120 litres in capacity

As standard, our 120 litre direct-pressurised hot water cylinders in high grade stainless steel are fitted with 2 x 3 kW immersion heaters with proven technology and quality.

Our 120 Litre unvented indirect cylinder has the following hot water heat-up time and recovery rates with standard 2 x 3 kW immersions fitted:

Hot water heating and recovery times for our 120 Litres direct unvented cylinders -130 Litre actual from Flexiheat UK

Hot water heating and recovery times

Upgraded immersion heater options 

We have the option of upgrading the immersion heaters to larger outputs for rapid heat recovery.

We can supply this 120 Ltr capacity direct unvented cylinder with 2 x 6kW immersion heaters, which can be wired in either 1 phase/240 volts (32 amps per immersion is required) or 3 phases (10.66 amps per phase is required); this will halve the recovery times stated above in the chart. We also must upgrade the standard temperature and pressure relief valve to a larger output model.

Or alternatively, you can have 1 x 6kW and 1 x 3kW immersion heater fitted, for a total kW input of 9kW; the standard 10kW T & P valve will remain if this configuration is used.

All of our unvented cylinders have a pressure test, and all are tested to 10 bar pressure and have a max working pressure of 5.5 bar.

Unvented hot water expansion system

The patented internal hot water expansion system, which uses a venturi valve to maintain an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel. This unvented system has a long product life because it has no moving parts, which reduces running and lifetime costs.

Internal air gap system for our direct unvented hot water cylinders- no external expansion vessel is required as this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance ensuring mains pressure hot water flow throughout the property whatever the heat source feeding the unvented hot water cylinder.

Our internal air gap and venturi valve system used on our direct unvented hot water cylinders- no external expansion vessel is required and little to no maintenance is required for the unvented hot water system.

 

As a result, our direct unvented cylinders need less space, pipework and plumbing fittings, making the installation process simpler and lowering both costs and time required for installation.

Unvented Direct Cylinder 120 Litres: Features and Benefits

  • Enhanced Venturi valve technology, which automatically replenishes the internal air gap within the unvented cylinder.
  • Dual immersion cylinder: 2 x 3kW immersion heaters as standard.
  • 3 bars of water pressure at the outlet (subject to incoming pressure).
  • Mains pressure hot water directly delivered—enabling high flow rates.
  • No expansion vessel or moving parts, ensuring low maintenance.
  • ErP “B” heat loss rating for reduce energy consumption
  • Benefits from an evolved design and quality manufacturing for improved performance at low flow rates.

120 litre unvented direct cylinder dimension

Our 120 litre stainless steel direct unvented cylinder has the following dimensions:

Dimensions drawing of our direct unvented cylinders in duplex stainless steel - 80 litre to 500 Litre - Flexiheat UK

Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models

 

The highly corrosion-resistant duplex stainless steel 120 Ltr capacity direct unvented cylinder has the following engineered dimensions in mm:

 

Direct unvented 120 Litre cylinder in stainless steel dimensions, which is a direct pressurised hot water cylinder and a dual immersion cylinder from Flexiheat UK

130L Direct pressurised hot water cylinder details highlighted in red – yes, we give you 10 more litres of capacity for free, as they can hold / have 130 Litres of capacity.

 

Our duplex stainless steel cylinders are available in both direct and indirect configurations as you can see in the following manual 

Download the installation & technical manual for our direct and indirect hot water cylinders

Unvented direct cylinder 120 ltr approvals

Our 120 ltr direct unvented cylinder we sell has been approved by the CE, BBA, and WRAS independent approvals (Water Regulations Approval Scheme—a certification body for domestic hot water heating products that assists businesses and customers choose safe products that comply with hot water regulations) and benefits from ISO, KIWA, and WRC approvals as well, proving the quality manufacturing process of our stainless steel cylinders.

Components supplied with our stainless steel unvented cylinder: 120L direct unvented cylinder

2 x 3kW immersion heaters manufactured in incoloy (a super austenitic stainless steel—with high resistance to oxidation), with a control thermostat and high-temperature thermal/energy cut-out thermostat.

Front access to the controls on our electric pressurised hot water cylinder.

A temperature and pressure relief valve to comply with the hot water unvented cylinder regulations.

A complete pressure-reducing valve combination valve/6-bar expansion relief valve (the maximum inlet pressure to the mains pressure hot water cylinder) for the cold water mains inlet 

A Tundish: A Tundish has a clear window that allows you to see if water is flowing from the pressure relief valve (PRV). This helps you identify potential issues with the unvented hot water system.

Heat loss ErP rating for this direct unvented cylinder

This direct unvented cylinder has an ErP level of “B” for the thermal insulation to reduce heat loss and ensure running costs are kept to a minimum, which is an excellent rating for an unvented direct cylinder.

The injected polyurethane foam thermal insulation, with an ODP=0 and a GWP=1 rating, is free of CFC/HCFC and provides 60mm of fire-retardant protection. Similar competitor products only have 40 mm insulation to reduce heat loss, and thus the ErP insulation ratings are lower than our direct unvented cylinder.

Delivery of the unvented cylinder

We deliver these direct unvented cylinders on a small pallet delivery service that comes on a lorry directly, with your responsibility to offload. We can upgrade the delivery service to have a tail lift at request to get the stainless steel 120L direct unvented cylinder to floor level.

Contact Flexiheat UK

Please contact us at 01202 822221 to answer any questions or use the company site contact email form to get more information or details, the current stock situation, delivery options, or a cost on the best 120 litre direct unvented cylinder/120Ltr unvented direct cylinder models on the UK market. These are manufactured from high-grade duplex stainless steel (a high-grade stainless steel), with a 25-year warranty, with WRAS independent approvals, have a built-in expansion system, and are a competitively priced cylinder.

150 Litre Direct Unvented Cylinder

150 Litre direct unvented cylinder

150 Litre direct unvented cylinder in highly corrosion resistant duplex stainless steel with 2 x 3kW immersion heaters for mains pressure hot water fromFlexiheat UK

150 Litre direct unvented cylinders in corrosion resistant duplex stainless steel for mains pressure hot water from Flexiheat UK

Our 150 Litre direct unvented cylinder is a competitively priced cylinder manufactured for mains pressure hot water and engineered in corrosion-resistant duplex stainless steel for high flow rates and longevity of performance via quality manufacturing processes.

So confident are we in the quality of our 150 litre unvented direct cylinder that for use in domestic locations, such as homes, flats, etc., they have a 25 year guarantee for these direct unvented cylinder models (the stainless steel hot water cylinder has a 25 year warranty; the ancillary components, i.e., the immersion heaters, control thermostat, etc., have a one year warranty.

An unvented water heating system delivers mains pressure hot water, enabling high flow rates for showers and baths without the need for a hot water booster or boost pump.

Patented unvented hot water expansion system

With a patented internal hot water expansion system, via a venturi valve to maintain an air pocket within the cylinder, it ensures an external expansion vessel is not required. This unvented system has a long product life because it has no moving parts, which reduces running and lifetime expenses.

Internal air gap system for our direct unvented hot water cylinders- no external expansion vessel is required as this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance ensuring mains pressure hot water flow throughout the property whatever the heat source feeding the unvented hot water cylinder.

Our internal air gap and venturi valve system used on our direct unvented hot water cylinders- no external expansion vessel is required and little to no maintenance is required for the unvented hot water system.

Due to this, our direct unvented cylinders require less space, pipework, and pipe fittings, which simplifies the installation and reduces install costs and time.

Features and benefits

  • Enhanced Venturi valve technology which automatically replenishes the internal air gap within the unvented cylinder.
  • 3 bars of water pressure at the outlet (subject to incoming pressure)
  • Mains pressure hot water – enabling high flow rates
  • No expansion vessel or moving parts, ensuring low maintenance
  • Energy cut out thermostat for saftey
  • Evolved design for improved performance at low flow rates

Download the installation notes for the internal air gap valve and system for unvented hot water cylinders

A 150L direct unvented cylinder is suitable for?

A rough guide is that 150 litre direct unvented hot water cylinders are suitable for flats or smaller homes with one or two bedrooms with one bath and/or shower.

However, people’s hot water usage patterns can vary from household to household. We prefer to give you the hot water usage data, and you can make the decision, as they say.

In the United Kingdom, we are required to keep DHW at 60°C since it eliminates the possibility of Legionella disease and is the minimum recommended water temperature.

If the stored water temperature is 60°C, the amount of required water is in red, to be blended down to 43°C (the maximum bathing temperature before scalding can occur).

Please use 10°C for England and Wales as the lowest cold-water wintertime temperature and use 5°C for Scotland and Northern Ireland.

If the incoming cold-water temp                                              is 10°C                                   is 5°C

A bath uses around 135 Litres of water at 43°C                    89 litres                                 94 litres

A standard 8 Litre shower head x 5 minutes                         30 litres                                 31 litres

And yes 5 minutes is the average showering time – say all the time and motion studies report.

A kitchen sink holds up to 20 litres of water                          16 litres                                   16.5 litres

N.B Washing up water temperature is normally 50C to ensure that grease is removed from dishes and cooking utensils.

Toilet sink taps—standard type—are around 4 litres per minute; “spray” type taps are 2 litres per minute and tend to be on for a brief period.

Please see the recovery time data below for our 150l direct cylinder to establish if this is the right 150l electric water heater for your circumstances and demands.

This 150 Litre volume direct unvented cylinder is the most popular seller in our range, however, should you wish a smaller volume cylinder, then please see the following webpage – 120 Litre direct unvented cylinder, this is our second most popular direct unvented cylinder that we sell.

150 litre unvented direct cylinder dimension

Our 150 litre stainless steel direct unvented cylinder has the following dimensions:

Dimensions drawing of our direct unvented cylinders in duplex stainless steel - 80 litre to 500 Litre - Flexiheat UK

Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models

 

 

For the 150 Litre capacity direct unvented cylinder manufactured in highly corrosion resistant duplex stainless steel, the dimensions are:

Direct unvented 150 Litre cylinder dimensions for our internal expansion unvented hot water system Flexiheat UK

150L direct highlighted in red

 

Download the installation & technical manual for our direct and indirect hot water cylinders

Being manufactured with high grade stainless steel and using quality manufacturing processes for the cylinder ensures long product life.

Hot water heat-up time and recovery rates for our direct unvented cylinder 150 litre volume

As standard our 150 litre direct pressurised hot water cylinders in high grade stainless steel are fitted with 2 x 3kW immersion heaters 

Our 150 Litre unvented indirect cylinder has the following hot water heat-up time and recovery rates with standard 2 x 3kW immersions:

 

Hot water heating and recovery times for our 150 Litre direct unvented cylinders from Flexiheat UK

Hot water heating and recovery times

Upgraded immersion heater options 

We have the option of upgrading the immersion heaters to larger outputs for rapid heat recovery –

We can supply this with 2 x 6kW immersion heaters which are be wired in either 1 Phase/ 240 volt (32 amps per immersion is required) or 3 Phase (10.66 amps per phase is required), this will half the recovery times stated above in the chart. We also must upgrade the standard Temperature and pressure relief valve to a larger output model

Or alternatively you can have 1 x 6kW and 1 x 3kW immersion heater fitted, for a total kW input of 9kW, the standard 10kW T & P valve will remain if this configuration is used.

All of our unvented cylinders have a pressure test, and all are tested to 10 bar pressure. The maximum working pressure is 5.5 bar.

Our unvented cylinders are available in direct and indirect configurations at a competitive price.

Components supplied with our stainless steel unvented cylinder: 150L direct unvented cylinder

2 x 3kW immersion heaters manufactured in incoloy (a super austenitic stainless steel—with high resistance to oxidation), with a control thermostat and high temperature thermal/energy cut-out thermostat.

Front access to the controls on our electric pressurised hot water cylinder

A temperature and pressure relief valve to comply with the unvented cylinder regulations.

A complete pressure reducing valve combination valve/6-bar expansion relief valve for the cold water mains inlet

A Tundish – A tundish has a clear window that allows you to see if water is flowing from the pressure relief valve (PRV). This helps you identify potential issues with the unvented hot water system.

Heat loss ErP rating for this direct unvented cylinder

This direct unvented cylinder, 150 litres in capacity, has an ErP level of “B” for the thermal insulation / to reduce heat loss and ensure running costs are kept minimum,which is a very good heat loss rating for an unvented direct cylinder.

The thermal insulation, which is a injected polyurethane foam is CFC/HCFC free, with an ODP=0 and a GWP=1 rating, being 60mm fire-retardant insulation. Similar products only have 40mm insulation to reduce heat loss , and thus the ErP insualtion ratings are lower than our direct unvented cylinder.

Unvented direct cylinder 150 litre approvals

Our 150 ltr direct unvented cylinder has the following approvals: CE, BBA, and WRAS independent approvals (Water Regulations Approval Scheme—a certification body for domestic hot water heating products that assists businesses and customers choose safe products that comply with regulations) and benefits from ISO, KIWA, and WRC approvals as well, proving the quality manufacturing process of our stainless steel cylinders.

Unvented cylinder delivery

We deliver these direct unvented cylinders on a small pallet delivery service that comes on a lorry, with your responsibility to offload. We can upgrade the delivery service to have a tail lift at request to get the stainless steel 150L direct unvented cylinder to floor level.

Contact Flexiheat UK

Please call us at 01202 822221 to answer any questions or use the contact form above to get more information, the current stock situation, delivery options, or a cost on the best 150 litre direct unvented cylinder/150Ltr unvented direct cylinder models on the UK market. These are made from high-grade duplex stainless steel (A high grade stainless steel) ,with a 25 year warranty, with WRAS independent approvals, have a built-in expansion system, and are a competitively priced cylinder.