500 Litre indirect unvented cylinder

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.

 

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.

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 table and heat exchanger rating detail

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

 

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.

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.