300 Litre direct unvented cylinder
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.
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:
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 230 volts (27 amps per heater) or three phases (9 amps per 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 – 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:
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:
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.
Dual Immersion Cylinder Range
/in Products /by flexiheatDual immersion cylinder range
A dual immersion cylinder or twin immersion direct cylinder are simply a hot water cylinder with two immersion heaters fitted to the cylinder.
They are often called an economy seven water heater, because the use economy seven off peak electricity to do most of the hot water heating, through the night time period.
Thus these direct hot water cylinders are not powered by a boiler, but with heating elements powered by a suitable electricity source.
Electricty is 100% energy-efficient, unlike an oil or natural gas boiler for example.
Hot water cylinders powered by twin immersions
A twin immersion hot water direct cylinder offers several practical and energy efficient benefits, particularly in UK homes, by using two separate electric heating elements (immersion heaters) positioned at different heights within the cylinder. Here’s a breakdown of the key advantages:
Flexible & efficient heating with a hot water cylinder with two immersion heaters
Ideal for economy 7 or time-of-use cheap electric tariffs
Better Control Over Hot Water Usage
Compatibility with Renewable Energy
Twin immersion cylinder range
Our stainless steel tank twin immersion unvented cylinder range consists of units from 100 Litres to 500 Litres in volume as detailed below.
Hot water cylinders with twin immersion heaters from flexiheat UK
The above chart shows specification details of the below cylinder.
Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models
Brocure is here for download
Download the Hot water cylinders direct and indirect unvented brochure from Flexiheat UK
Full installation manual is here for download
Flexiheat manual for direct & indirect hot water cylinders
Special specification tanks are also available in many sizes.
Note: Customised products are non-returnable.
Unvented cylinder
Most modern twin immersion cylinders are unvented, providing consistent, high-pressure hot water from the mains supply.
Unvented cylinders are sealed and filled directly from the mains water supply, designed to provide hot water at high pressure.
Dual element immersion heater sizing
As a rough guideline, the typical consumption rates (hot water requirements per person per day) are as follows:
Patented unvented hot water expansion system
The innovative internal hot water expansion mechanism, which employs a venturi valve to keep an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel and is space saving.
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.
Our direct unvented hot water cylinders have an internal air gap and venturi valve technology that requires no expansion vessel and little maintenance.
Without moving parts, this unvented system provides a long product life and minimal operating and lifetime costs.
Internal air gap system for our direct unvented hot water cylinders: no external expansion vessel is needed because this self-sustaining air gap requires little to no maintenance and ensures mains pressure hot water flow throughout the property with our double immersion cylinder range.
Immersion heater
The immersion heating elements are screwed into the female tappings installed on the cylinder.
The 100 to 500 litre electric water heater / unvented cylinders are twin immersion cylinders with two 3 kW incoloy immersion heaters for rapid heat recovery as standard.
Additionally, we offer three 3 kW incoloy immersion heaters that may be installed on our 215 litre to 500 litre direct unvented cylinder versions or three 6 kW dual phase immersion heaters that can be wired either single or three phase, for a total power input of 18 kW.
Incoloy immersion elements
Our immersion heaters are high-quality units manufactured of Incoloy 825 stainless steel and equipped with a temperature control thermostat and an energy cutout thermostat.
Power Requirement for immersion heaters
These immersion heaters can be powered by single or three-phase supplies.
For the 3kW heating elements – these are 240 Volt / 1Phase powered and require 13 Amps of power per element.
If you upgrade to the 6kW heating elements – these can be either 1 phase / 240 volt or 3 phase / 415 Volt wired – if on 1 phase these require a supply of 26 Amps per heater, on three phase they require 9 Amps per phase for each element.
Domestic hot water heat up times
Please double these times if using only one of the 3kW immersion heaters i.e. using off peak electricity to heat overnight.
or half these times if using the upgraded 6kW immersion heaters
If you wish to contact us with a question or to find out further information
Should you require further assistance,information,questions on the product or to purchase / order one of our Dual or Twin immersion cylinder range,which are guaranteed for 25 year domestic use against faulty materials of the stainless steel tank ( 5 years guaranteed for commercial use) then please contact our customer sales team on 01202 822221 or click here for our email contact form to send an email
500 Litre Direct Unvented Cylinder
/in Products /by flexiheat500 Litre Direct Unvented Cylinder
Our 500 Litre direct unvented cylinder is built with corrosion-resistant duplex stainless steel and is at an affordable price. This unvented hot water cylinder for mains pressure hot water uses proven technology and quality production to provide high flow rates and a long product life.
Flexiheat UK warranties this 500 Litre stainless steel unvented direct cylinder for 25 years for household use. Hot water cylinders heated by 100% energy-efficient immersion heaters (100% heat transmission) heat bathrooms and showers.
Direct types are utilised when gas or oil is unavailable, a heat pump is unviable, or people desire carbon-free electricity to heat their water.
This electric powered 500 litre unvented hot water storage cylinder is made from stainless steel making them suitable for hard and soft water areas of the UK.
This water heater can be powered PV solar panels (photovoltaics) which produce solar electricity for off grid or carbon free power. An inverter is required for the immersions – to convert DC to AC to power the immersions correctly.
Patented unvented hot water expansion system
The innovative internal hot water expansion mechanism, which employs a venturi valve to keep an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel.
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.
Our direct unvented hot water cylinders have an internal air gap and venturi valve technology that requires no expansion vessel and little maintenance.
Without moving parts, this unvented system provides a long product life and minimal operating and lifetime costs.
Internal air gap system for our direct unvented hot water cylinders: no external expansion vessel is needed because this self-sustaining air gap requires little to no maintenance and ensures mains pressure hot water flow throughout the property regardless of the heat source.
Our direct unvented hot water cylinders use an internal air gap and venturi valve technology to eliminate the need for an expansion vessel and reduce maintenance.
Our 500-litre electric hot water system requires less space, pipes, and plumbing connections, simplifying installation and saving time and money.
What applications is a 500L direct unvented cylinder appropriate for?
500 litre direct unvented hot water cylinders are suitable for 4-bedroom homes with two bathrooms/showers or more or those with a high hot water demand.
However, hot water usage preferences vary.
See our 500L unvented direct cylinder recovery time data below to decide if this electric water heater is best for you.
This 500 Litre volume direct unvented cylinder is a popular seller in this range; however, if you require a higher volume cylinder, please visit the following webpage: direct unvented cylinder range.
Hot water heating and recovery times for a our direct unvented cylinder 500 Litres from Flexiheat UK
High-quality stainless steel 500 Litre direct-pressurised hot water cylinders include 2 x 3kW immersion heaters.
The typical 2 x 3kW immersion heaters in our 500 Litre unvented electric powered direct cylinder provide the following hot water heat-up and recovery rates:
Water heating and recovery times in minutes for our 500 litre unvented direct cylinder.
Our 80 to 500 litre direct unvented hot water cylinders are listed on this page: Unvented Direct Cylinder in Stainless Steel.
Upgraded immersion heater options.
On both the 2 and 3 immersion models, we can increase immersion heater outputs for faster heat recovery.
Three 3 kW immersion electric heaters can be added to this 500-litre direct unvented cylinder for a total of 9 kW and 214 minutes from 10°C to 65°C.
We can supply this 500 Ltr direct unvented cylinder with 3 x 6 kW immersion heaters. These heaters can output 18 kW from a single phase at 230 volts (27 amps per heater) or three phases (9 amps per phase). This method heats 500 litres of water from 10°C to 65°C in 107 minutes.
Since the standard temperature and pressure relief valve is rated for 10kW, we must upgrade it.
Our manufacture tests all unvented hot water cylinders at 5.5 bar and 10 bar.
If you want a bigger output of up to 36 kW for a 500 Litre direct water heater, please consult this webpage: Commercial electric water heater range.
Unvented Direct Cylinder 500 Litres: Features and Benefits.
Unvented cylinders’ internal air gap is automatically supplied by improved Venturi valve technology.
The standard dual immersion cylinder has 2 x 3 kW immersion heaters, which can be increased to 3 × 3 kW or 3 × 6 kW.
Our straight unvented hot water cylinders with inbuilt expansion require no external expansion vessels.
Our integrated expansion mechanism straight unvented hot water cylinders don’t need extra expansion vessels, making installation in tight spaces easier.
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
Dimensions for a 500-litre unvented direct cylinder
Our 500-litre stainless steel direct unvented cylinder has the following dimensions:
Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models
The dimensions in millimetres for the corrosion-resistant duplex stainless steel 500 Ltr capacity direct unvented cylinder are as follows:
500L direct cylinder with internal expansion dimensions
The full brochure and installation manuals are here (Which cover both the direct models and indirect models ) :
Download the Hot Water cylinders direct and indirect unvented brochure from Flexiheat UK
Download the installation and technical manual for our direct and indirect hot water cylinders.
Unvented Cylinder Certifications for our 500 litre unvented indirect cylinders
Our 500 Ltr direct unvented cylinder has been certified by CE, BBA, and WRAS, independent organisations that ensure hot water heating products are safe and compliant, in addition to ISO, KIWA, and WRC certifications.
Warranty for the 500 Litre Hot Water Cylinder
For domestic use in homes and apartments, our 500 Litre unvented direct cylinders have a 25-year warranty because we trust them. Immersion heaters and control thermostats are insured for one year after purchase, however the stainless steel hot water cylinder is guaranteed for 25 years.
Contact Flexiheat UK
Please contact us at 01202 822221 if you have any queries or use site contact email form for more information or specifics, the current stock situation, or a price on the best 500 litre direct unvented cylinder/500Ltr unvented direct cylinder model on the UK market. We manufacturer these models from high-grade duplex stainless steel, which has a 25-year warranty for residential customers (5 years for commercial use), a low heat loss rating, and WRAS independent approvals.
400 Litre Direct Unvented Cylinder
/in Products /by flexiheat400 Litre Direct Unvented Cylinder
400 litre unvented direct cylinder in stainless steel
Our 400 Litre direct unvented cylinder is built with corrosion-resistant duplex stainless steel and is reasonably priced. This unvented hot water cylinder for mains pressure hot water was created with high flow rates and a long product life in mind, utilising proven technology and a quality manufacturing method.
Flexiheat UK offers a 25-year warranty for household usage on this 400 Litre unvented direct cylinder in stainless steel. These hot water cylinders are heated by 100% energy-efficient immersion heaters (100% heat transfer) and provide water heating for bathrooms and showers.
When gas or oil is unavailable, or a heat pump is unviable or individuals prefer to heat their water with carbon-free electricity, electric water heating is commonly used thus the term direct models.
Patented unvented hot water expansion system
The innovative internal hot water expansion mechanism, which employs a venturi valve to keep an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel.
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.
This unvented system has a long product life because it has no moving parts, lowering operating and lifetime expenses.
Internal air gap system for our direct unvented hot water cylinders: no external expansion vessel is required because this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance and ensures mains pressure hot water flow throughout the property regardless of the heat source feeding the unvented hot water cylinder.
Our direct unvented hot water cylinders use an internal air gap and venturi valve technology, which eliminates the need for an external expansion vessel and requires minimal maintenance.
As a result, our 400 litre electric hot water system requires less space, pipes, and plumbing connections, simplifying the installation process and saving installation costs and time.
What applications is a 400L direct unvented cylinder appropriate for?
A basic guideline is that 400 litre direct unvented hot water cylinders are appropriate for larger residences, such as a 4-bedroom house with two bathrooms/showers or more, or for properties with a high need for hot water.
People’s hot water consumption habits, however, can differ from one another.
Please see the recovery time data for our 400L unvented direct cylinder below to determine whether this is the right electric water heater for your requirements.
This 400 Litre volume direct unvented cylinder is a popular seller in this range; however, if you require a higher volume cylinder, please visit the following webpage: direct unvented cylinder range.
Hot water heating and recovery times for a our direct unvented cylinder 400 Litres from Flexiheat UK
Our 400 Litre direct-pressurised hot water cylinders in high-grade stainless steel come standard with 2 x 3kW immersion heaters.
Our 400 Litre unvented electric powered direct cylinder has the following hot water heat-up time and recovery rates with the standard 2 x 3kW immersion heaters installed:
water heating and recovery times in minutes for our 400 litre unvented direct cylinder flexiheat uk
If you need a different size direct unvented hot water cylinder, we have a whole variety from 80 to 500 Litres, which are detailed on this page: Unvented Direct Cylinder in Stainless Steel variety.
Upgraded immersion heater options.
We can upgrade the immersion heaters to higher outputs for faster heat recovery on both the 2 and 3 immersion model options.
This 400-litre direct unvented cylinder can also be equipped with 3 x 3 kW immersion electric heaters, for a total kW output of 9 kW and a recovery time of 180 minutes from 10°C to 65°C (or 3 hours).
If desired, we can deliver this 400 Ltr direct unvented cylinder with 3 x 6 kW immersion heaters. These heaters can be connected to either a single phase at 230 volts (27 amps per heater) or three phases (9 amps per phase), for a total power output of 18 kW. This system heats the water from cold (10°C) to 65°C in 86 minutes for the 400 litres of volume.
We must also change the basic temperature and pressure relief valve to a higher output model, as the normal valve is rated for 10kW of power.
All our unvented hot water cylinders are pressure tested at the factory, with a maximum working pressure of 5.5 bar and a test pressure of 10 bar.
If you want a bigger output of up to 36 kW for a 400 Litre direct water heater, please consult this webpage: Commercial electric water heater range.
Unvented Direct Cylinder 400 Litres: Features and Benefits.
Improved Venturi valve technology automatically supplies the internal air gap of the direct unvented cylinder.
The dual immersion cylinder comes standard with 2 x 3 kW immersion heaters but may be upgraded to 3 × 3 kW or 3 × 6 kW.
Our direct unvented hot water cylinders with an inbuilt expansion system do not require any external expansion vessels to be installed.
Our direct unvented hot water cylinders, which have an integrated expansion mechanism, do not require external expansion vessels to be fitted, making installation in compact places easier.
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
Dimensions for a 400-litre unvented straight cylinder
Our 400-litre stainless steel unvented cylinder has the following dimensions:
Unvented direct hot water cylinders in duplex stainless steel – Dimensions drawing for 80 Litre to 500 Litre models from Flexiheat UK
The dimensions in millimetres for the extremely corrosion-resistant duplex stainless steel 400 Ltr capacity direct unvented cylinder are as follows:
400L direct cylinder with internal expansion dimensions
The full brochure and installation manuals are here (Which cover both the direct models and indirect cylinders/ indirect models ,which have a coil and are powered by a conventional boiler):
Download the Hot Water cylinders direct and indirect unvented brochure from Flexiheat UK
Download the intallation and technical manual for our direct and indirect hot water cylinders.
Approvals for unvented direct cylinders of 400 Litre in capacity
The 400 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 comply with regulations, as well as ISO, KIWA, and WRC certifications, demonstrating that our stainless steel direct cylinders are manufactured to high standards.
Warranty for the 400 Litre Hot Water Cylinder
We are so confident in the quality of our 400 Litre unvented direct cylinders that they come with a 25-year warranty for use in residential applications such as homes and apartments. The guarantee covers the stainless steel hot water cylinder for 25 years, while other parts, such as immersion heaters and control thermostats, are covered for one year from the date of purchase.
Contact Flexiheat UK
Please contact us at 01202 822221 if you have any queries or use site contact email form for more information or specifics, the current stock situation, or a price on the best 400 litre direct unvented cylinder/400Ltr unvented direct cylinder models on the UK market. We manufacturer these models from high-grade duplex stainless steel, which has a 25-year warranty for residential customers and trade customers (5 years for commercial use), a low heat loss rating, and WRAS independent approvals.
Renewable LPG – the present and future for Caravan heating & hot water production
/in News /by flexiheatRenewable LPG – the present and future for Caravan heating & hot water production
LPG Gas and why it’s so popular for caravan and park home heating and hot water
Liquified petroleum gas (LPG) is currently the preferred fuel for heating and hot water generation in the caravan and park home sectors due to its accessibility, clean combustion, and immediate heat generation. However, as we strive for a net-zero society, there is concern about the future prospects of this widely used off-grid gas.
LPG, available in portable cylinders or bulk tanks, serves as an on-site, on-demand fuel source for heating applications in static park homes and communal buildings.
The future of LPG gas
With the UK Government’s goal to reduce carbon emissions in all industries and the decreasing trend in oil and natural gas extraction, the LPG manufacturers must identify environmentally friendly alternatives to LPG for the caravan heating and hot water generation sector.
The LPG gas sector is already making significant progress in transitioning to sustainable, low-carbon alternatives.
Revolutionising caravan heating by utilising renewable liquid gases (RLGs)
The LPG sector is dedicated to shifting entirely to renewable sources and has a well-defined plan to do this by 2040.
As the industry focuses on creating low-carbon heating alternatives in accordance with this goal, two types of renewable liquid gases (RLGs) stand out as promising solutions for the caravan heating sector: BioLPG, also known as Biopropane and Renewable DiMethyl-Ether (rDME).
Both BioLPG and rDME provide ecologically sustainable alternatives to regular LPG without compromising performance. BioLPG is a chemical compound that is exactly the same as LPG, whereas rDME is a chemical compound that is comparable to butane and propane. Furthermore, all alternatives are fully compatible with all your current LPG appliances. This implies a reduction in carbon emissions without the inconvenience or extra expense of acquiring new boilers or water heaters.
In addition, it is possible to mix rDME and BioLPG with conventional LPG, enabling a progressive transition over a period of time. This sets them apart from other biofuel alternatives, since they cannot be mixed with the substances they are replacing and also need the added cost of acquiring new appliances.
BioLPG and rDME are classified as a “drop-in” replacements fuel for standard LPG and are derived from a varied combination of sustainable biological sources and methods, such as agricultural or home waste, energy crops, or recycled carbon.
Renewable liquid gases can reduce carbon emissions by up to 90%. They have similar levels of nitrogen oxides (NOx), sulphur oxides (SOx), and particulate matter as traditional LPG, which helps improve air quality.
Lowering environmental impact
These renewable liquid gases serve as a direct substitute for conventional LPG without the need for any modifications. They can be utilised with existing tanks, heating systems, resulting in cost savings for consumers and a low environmental impact.
Suppliers offer readily accessible BioLPG now, which is marketed under certain brand names. Both bioLPG and rDME may be mixed with traditional LPG, allowing consumers who wish to transition to a more environmentally friendly heating fuel solution and convert to these low-carbon gas fuels.
Boilers for static caravans
The most common boilers for static caravans. glamping pods or park homes are combination boilers that do both the heating and domestich hot water requirements. All of our our lpg combi boilers for caravans can be used with the drop in replacement bio LPG gases without any modification to the burner required.
Direct Pressurised Hot Water Cylinders
/in Guides /by flexiheatDirect Pressurised Hot Water Cylinders for Efficient Domestic Hot Water Heating
Direct pressurised hot water cylinders are the most popular electric powered water heater or electric heating hot water system on the UK market.
Introduction to direct hot water cylinders
Quality manufacturing and proven technologies are essential in the production of direct unvented cylinders, ensuring a high level of performance and reliability.
Direct hot water cylinders are a perfect solution for properties with limited space, as they can be easily installed and maintained, reducing the need for additional plumbing.
Benefits of Direct Unvented Systems
Direct unvented systems offer numerous benefits, including high flow rates, efficient heating, and cost-effective operation, making them a popular choice for homes and businesses.
The use of energy cut out thermostats, temperature and pressure relief valve and control thermostats in direct unvented cylinders helps to reduce heat loss and minimize energy consumption, while also providing a high level of control and safety over the water heating system.
Unvented cylinders are available in a range of capacities, from 80 Litre to 5,000 Litre, making them suitable for properties of all sizes, and can be used to supply hot water to multiple showers and baths.
For our 80 to 500 Litre direct pressurised cylinder range which come with a 25-year warranty for domestic use (5 year warranty for commercial use), please see the dedicated webpage –unvented direct cylinders
Direct unvented systems are designed to provide a reliable and consistent supply of hot water, making them ideal for locations with high demand, such as commercial properties, schools, hospitals etc. This webpage details our commercial electric water heaters
The benefits of direct unvented systems also extend to the environment, as they can help to reduce energy consumption and minimize waste, making them a more sustainable option.
Direct pressurised hot water cylinders are environmentally friendly due to the gradual phasing out of gas power sources.
Materials and Construction for Durability – Stainless steel
Stainless steel is a popular material for direct unvented cylinders due to its high level of corrosion resistance and durability, ensuring a long lifespan and minimal maintenance.
Quality manufacturing is essential in the production of direct unvented cylinders, ensuring that they are built to last and can withstand the demands of frequent use, while also providing a high level of performance and reliability.
The use of duplex stainless steel in cylinders, provides additional strength and resistance to corrosion, making them ideal for use in harsh environments.
Direct unvented cylinders are designed to be compact and space-efficient, making them perfect for properties with limited space, while also providing a high level of performance and reliability.
Insulation of the electric pressurised unvented cylinder
The construction of direct unvented cylinders is designed to minimize heat loss and optimize energy efficiency, making them a cost-effective option for homes and businesses.
Direct hot water cylinders should feature 40mm insulation to reduce heat loss. Our units have 60mm insulation for lower heat losses for our 80 to 500 Litre models.
Installation and Maintenance Considerations for direct unvented cylinders
Direct unvented cylinders require careful installation to ensure safe and efficient operation, and it’s essential to follow the manufacturer’s instructions and guidelines.
Regular maintenance is essential to extend the lifespan of the cylinder and prevent issues, such as corrosion and scale buildup, and it’s essential to check the direct pressurised cylinder regularly for signs of wear and tear.
The use of quality materials and construction in direct unvented cylinders helps to minimize the need for maintenance, while also providing a high level of performance and reliability.
The installation process includes components such as combination valves and immersion heaters.
Direct unvented cylinders are designed to be compact and space-efficient, making them easy to install and maintain, even in properties with limited space.
It’s also essential to consider the delivery and installation prices when choosing a direct unvented cylinder, as these can vary depending on the manufacturer and supplier.
Contact Flexiheat UK
For any direct pressurised cylinder requirements, or should you require anymore assistance or information, please contact our sales team on 01202 822221 or click here for our email contact form.
Buffer Vessel Sizing for Hydronic Heating Systems
/in Guides /by flexiheatBuffer Vessel Sizing for Hydronic Heating Systems
Buffer vessels are essential components in hydronic heating systems, providing thermal storage capacity that improves system efficiency, reduces equipment cycling, and enhances overall performance. Proper sizing of these vessels is critical to achieving optimal system operation. This guide covers the principles, calculations, and considerations necessary for correctly sizing buffer vessels in hydronic heating systems and get optimal performance from your thermal storage tanks.
What is a Buffer Vessel?
A buffer vessel (also called a buffer tank or thermal store) is a water storage tank that acts as a thermal energy reservoir or heat sink within a hydronic heating system. It provides hydraulic separation between the heat source and the heating distribution system, storing excess heat for later use and helping to manage system flow rates and temperatures effectively.
Why Buffer Vessels Are Important
Key Factors in Buffer Vessel Sizing
Heat Source Characteristics
The type and operational characteristics of the heat source significantly impact buffer vessel sizing:
Modulation range: Heat sources with limited modulation require larger buffers
Minimum run time: Sources with longer minimum run times need greater storage
Response time: Slower-responding heat sources benefit from larger buffers
Minimum load requirements: Buffer vessels help manage minimum load issues
System Load Profile
Understanding the heating demand profile is crucial for proper sizing of a buffer tank or vessel:
Temperature Differential (ΔT)
The usable temperature range within the buffer vessel directly affects its capacity:
Calculation Methods for Buffer Vessel Sizing
Volume Based on Heat Source Characteristics
For conventional boilers and heat pumps:
Buffer Volume (L) = Minimum Heat Output (kW) × Minimum Runtime (minutes) × 60 / (ΔT × 4.18)Where:
Volume Based on Thermal Mass Requirements
For systems requiring specific thermal storage capacity:
Buffer Volume (L) = Required Energy Storage (kWh) × 860 / ΔTWhere:
Rule-of-Thumb Methods of buffer tank
While detailed calculations are preferred, some common industry rules of thumb include:
Specific Sizing Considerations by Heat Source Type
Heat Pumps
Heat pumps generally require larger buffer vessels due to:
For air-source heat pumps, a minimum of 40-50 litres of water volume per kW of heat pump capacity is recommended.
For more detail on our buffer tanks for heat pump range, please click here – Buffer tanks for heat pumps
Ground source heat pump buffer vessel sizing
Buffer vessel or buffer tannk sizing for ground source heat pump systems requires careful consideration of the unique operational characteristics of GSHPs. The lower temperature differentials and limited modulation capabilities of these hvac systems typically necessitate larger storage tank volumes than conventional heating systems.
When properly sized and installed, buffer vessels help GSHPs achieve their full efficiency potential while protecting the significant investment in equipment and ground loops. For optimal results, buffer sizing should be integrated into the overall system design process, taking into account both the ground source heat pumps characteristics and the specific heating (and possibly cooling) demands of the building.
Ground Source Heat Pump Characteristics
GSHPs differ from other heating systems in several key ways that affect buffer vessel sizing:
Why GSHPs Need Buffer Vessels
Special Considerations for GSHP Buffer Sizing
System Minimum Run Time
GSHPs typically require longer minimum run times to maximize efficiency and protect equipment:
The sizing formula becomes particularly important:
Buffer Volume (L) = Minimum Heat Output (kW) × Minimum Runtime (minutes) × 60 / (ΔT × 4.18)Temperature Differential (ΔT)
GSHPs operate most efficiently with specific temperature differentials:
This smaller ΔT necessitates larger buffer vessels compared to high-temperature systems.
Recommended Sizing Guidelines
For ground source heat pump hvac systems , industry standards recommend:
Buffer Configuration for GSHPs
Four-Pipe Configuration
The preferred setup for GSHPs is the four-pipe configuration:
Biomass Boilers
Biomass boiler hydronic systems typically require the largest buffer vessels due to:
For wood pellet or log boilers, 50-100 litres of water volume per kW of boiler capacity is standard for the thermal storage tanks.
Condensing Gas Boilers
Modern condensing boilers generally require smaller buffers due to:
However, buffer vessels are still beneficial for:
Combined Heat Sources
When additional heat sources or multiple heat sources are connected to a single buffer tank:
Installation Considerations
Stratification and Connections
Proper connection placement enhances thermal stratification in the thermal store:
Hydraulic Integration
Chilled water buffer sizing
For a chiller system.We have a dedicated webpage on chilled water buffer tank sizing here – Chilled water buffer tank sizing
Insulation Requirements
Buffer vessels should be well-insulated to minimize standby losses:
Common Sizing Errors
Undersizing
Consequences of insufficient buffer capacity include:
Oversizing a buffer tank
Potential issues with excessively large buffers:
Advanced Considerations
Low-Temperature Systems such as a heat pump system
Underfloor heating and other low-temperature distribution systems:
High-Temperature Systems
Radiator and high-temperature systems:
Renewable Integration
When combining with solar thermal or other renewables:
Conclusion
Proper buffer vessel sizing is essential for hydronic heating system performance. While various calculation methods exist, the optimal size depends on a thorough understanding of heat source characteristics, system load profiles, and operational requirements. When properly sized and installed, buffer vessels improve system efficiency, extend equipment life, and enhance overall comfort.
170 Litre Direct Unvented Cylinder
/in Products /by flexiheat170 Litre direct unvented cylinder – Electric water heater
Looking for a 170 litre direct unvented cylinder in duplex high grade stainless steel? then we have you covered as we supply a 175 litre direct unvented cylinder which covers this direct hot water cylinder capacity.
Manufactured in the UK, with quality manufacturing processes, our 170 litre direct unvented cylinder full conforms to the “G3” unvented cylinder building regulations, having WRAS, NSF WRC, CE and KIWA independent approvals.
This 170L 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 170 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 170 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 170L 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.
No external expansion vessel is required
This 170 litre direct unvented cylinder has a patented internal hot water expansion system which eliminates the need for a remote 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 170 litre direct cylinder. Also having low maintenance requirements.
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.
Stainless steel direct unvented cylinder – 170 Litre
Our 170 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.
Technical specification – 170 litre direct hot water cylinder
Our 170 litre direct unvented hot water cylinder has the following dimensions (yes our unit is 175 Litres of storage – so covers the 170 litre direct unvented cylinder requirements)
Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models.
Our 170L unvented direct cylinders are fitted with a secondary DHW return connection as standard.
We have a full range of direct unvented cylinders for 80 to 500 Litre – should you require another size cylinder, please see the following webpage – Unvented direct cylinders in stainless steel 80 to 500 Litres
Our 170 litre hot water cylinder dimensions are as follows
170 Litre direct unvented cylinder – it’s actual 175 Litres of volume.
Our next volume down cylinder is our 150 Litre direct unvented cylinder , or should you require the next size up, then please see the – 200 Litre direct unvented cylinder, which actually has a storage volume of 215 Litres.
Hot water heat-up time and recovery rates for our direct unvented hot water cylinder, 170 litres (175 Litres actual) in capacity
As standard, our 170 litre direct-pressurised hot water cylinders in high-grade stainless steel are fitted with 2 x 3kW immersion heaters (option to upgrade to 2 x 6kW immersion heaters) with proven technology and quality. Following are the hot water heat up times for the standard configuration (2 x 3kW)
Water heating and recovery times in minutes for our 170 litre unvented direct cylinder with the standard 2 x 3kW immersion heaters.
The full brochure (covers both direct and indirect configurations) and installation manuals are here for direct download –
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
170 Litre direct cylinder unvented – standard components
Our 170 litre direct unvented cylinder models come complete with the following full unvented kit to suit the product –
2 x 3kW Incoloy immersion heaters including control and energy cut out thermostat for rapid heat recovery and saftey.
60mm fire retardant injected polyurethane foam insulation on the cylinder ensures reduced heat loss and running costs.
22mm Cold water inlet pressure reducing valve /expansion relief in a combination valve
22mm Hot water outlet for high flow rates
Dual thermostat (Control thermostat and Energy cut-out heat thermostat)
Tundish
All controls and connections have front access.
Temperature and pressure relief valve mounted to the direct unvented cylinder.
Pressure relief valve setting 7 bar.
90ºC temperature relief valve setting.
ErP heat loss rating – better than “B” for the heat loss rating, which greater than similar products on the market.
Product lifetime guarantee of 25 years for domestic use – 5 years for commercial use.
170 litre unvented direct 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, maintain and service unvented hot water storage systems. In the UK, building control will not issue a building regs certificate unless a qualified person has fitted the direct unvented hot water cylinder.
To locate a “G3” qualified heating engineer close to you, please consider using this website – gas safe register
Contact Flexiheat UK
For further information, check stock availability, lead time, delivery, prices or to purchase our 170 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.
200 Litre Direct Unvented Cylinder Water Heater
/in Products /by flexiheat200 Litre direct unvented cylinder – Electric water heater
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.
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.
Technical 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)
Unvented direct hot water cylinders – Dimensions drawing for 80 Litre to 500 Litre models
Our 200 litre hot water cylinder dimensions are as follows
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.
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
/in Products /by flexiheat300 Litre direct unvented cylinder
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.
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:
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 230 volts (27 amps per heater) or three phases (9 amps per 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
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
300 litre unvented direct cylinder dimensions
Our 300 litre stainless steel direct unvented cylinder has the following dimensions:
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:
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
/in Products /by flexiheat210 Litre indirect unvented cylinder
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
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.
Or if you require another volume, please see our webpage – Indirect unvented cylinders 80 to 500 Litres which details the full range available.
The product offers key specifications, features, and benefits
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.
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.
Our indirect hot water heater dimensions diagram
Dimension data in “mm” for the above specification diagram
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.
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
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 – 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.