Indirect Sealed System Thermal Store

130 | 150 | 175 | 215 | 255 LITRES

An indirect sealed system thermal store cylinder for use with a conventional boiler with electric back-up

The Plumbing Group are at the forefront of water heating technology. We are changing the way you think about water heating installations.  The ThermaCoil is a mains pressure open vented thermal storage system. It does not require safety valves and has no external discharge requirements.

ThermaCoil thermal storage systems works by reversing the function of the Primary (Heating) and Secondary (Domestic) water. The Primary water is stored in the cylinder and heated by either a boiler (indirect) or immersion heaters (Direct). When heated by a boiler, the water can also be pumped around either a wet central heating system or an under-floor heating system.

The Secondary water comes directly from the mains and passes through a specially designed finned heat exchanger coil which draws heat from the ThermaCoil. This water then passes through a thermostatic mixing valve which blends the water to the correct temperature before it reaches the taps.

Indirect Sealed System Thermal Store

Indirect Sealed System Thermal Store



External expansion vessels are not required and wiring is the same as any traditional Y, S, or W plan system.

ThermaCoil Indirect thermal stores do not require any annual maintenance. This complies with the Hot Water Associations specification for thermal stores.

The ThermaCoil Indirect is supplied without a sealed system kit, it is available to purchase as an optional extra. The standard ThermaCoil indirect is suitable for use as either an open-vented or sealed heating systems thermal store with the appropriate sealed system kit.

BS6700: 1997 states that with unvented cylinders, the “maintenance and periodic easing of temperature relief valves is particularly important.” This is a landlord’s responsibility in tenanted properties and annual checks must be carried out by a CITB trained person or installer, having G3 approval.

As ThermaCoil Indirect is vented and therefore inherently safe, there is no requirement for a safety discharge, and it is not subjected to building control regulations – thus simplifying installation and system maintenance enormously for the landlords or homeowners.

ThermaCoil Indirect is a mains pressure vented hot water thermal store suitable for open vented and sealed heating systems. The unit can be fitted with a conventional ‘S’ plan, ‘Y’ plan, or a control system of your choice and the controls can be plumbed inside the appliance giving a clean finish within the airing cupboard. The header tank can be sited on top of the unit or remotely for
maximum installation flexibility.

Available in five sizes ranging from 150 litres through to 255 litres. Our largest model is capable of satisfying the hot water demands of a property with 6 bedrooms, 2 bathroom and 2 separate shower room.

All models are pressure tested to 10 bar and come complete with two immersion elements and a TMV 2/3 blending valve.

It is not commonly known that uncased foam insulated cylinders can lose up to 40% of their insulation value within weeks of manufacture. These uncased cylinders can also emit dangerous smoke if involved in a fire, therefore, the ThermaCoil Indirect has been designed with an outer metal case. As with all ThermaCoil thermal stores there is no release of o-zone depleting substances
or harmful emissions. Industry leading CFC / HCFC free, (ODP=0, GWP=1) 60mm fire retardant insulation foam is used to provide exceptionally low standing heat loss.

ThermaCoil Indirect models are designed to be fed directly from the mains. They fulfil the requirements of Water Regulations and therefore do not require a check valve to be fitted to the supply pipe. The performance of the ThermaCoil Indirect is directly related to the adequacy of the cold supply to the dwelling. This must be capable of providing for those services which could be required
simultaneously and the maximum demand should be calculated.

ThermaCoil Indirect will operate at dynamic pressures as low as 1.5 bar (at the appliance) which must be available when local demand is at its maximum, but the preferred range is between 2 and 3.5 bar. As a general guideline, although a 15mm external service may be sufficient for the smaller dwelling with one bathroom, a 22mm service is preferred (25mm MDPE) and should be the minimum for larger dwellings.

This appliance is suitable for use with plastic pipework as long as the material is recommended for the purpose by the manufacturer and is installed fully in accordance with their recommendations.

The Domestic Heating Compliance Guide published in May 2006 requires a water treatment device to be fitted where the hardness is greater than 200ppm. Full details are given in the Design and Installation manual supplied with all ThermaCoil Indirect units.

Indirect Sealed System Thermal Store Heat Loss Performance


Features of a ThermaCoil Indirect Sealed System Thermal Store

  • 10-Year cylinder and 3-Year parts warranty
  • No risk of legionella.
  • Sizes 130L to 255L capacity
  • Cylinder manufactured from high grade Duplex stainless steel
  • 60mm fire retardant insulation minimising heat loss
  • 100% CFC/HCFC free
  • Long life with no internal moving parts
  • No external expansion vessel, quicker installation
  • 3 Bar pressure at outlets
  • All sizes WRAS approved
  • Designed & manufactured in the UK

ThermaCoil Indirect Sealed System Thermal Store Schematic

Indirect Sealed System Thermal Store

ThermaCoil Indirect Sealed System Thermal Store Product Construction – Typical

Immersion heater ☞ 3kw, 240V, 1ph, Incoloy 825, with thermostat incl. cut-out
Thermal insulation ☞ CFC/HCFC free, (ODP=0, GWP=1), 60mm fire retardant insulation*
Outer casing ☞ P200 Plastisol
Inner cylinder ☞ Duplex stainless steel
Heating coil ☞ High performance, finned
Indirect thermostat ☞ Twin thermostat with independent reset, 30-70ºC


ThermaCoil Indirect Sealed System Thermal Store Product Specification

Pressure test☞ Tested to 10 bar
Approvals☞ BBA, CE, WRAS, KIWA, ISO, WRC
Guarantee☞ Internal cylinder 10 years* Ancillary components 3 year
Direct thermostat☞ Element thermostat, nominal setting 87ºC
Indirect model ☞ 22mm diameter stainless steel high performance coil & outlet with 1 immersion heater
Direct model ☞ 130L – 255L fitted with 2 immersion heaters
Manufacturing ☞ All UK using state-of-the-art robot technology

To download or print digital copies of ThermaCoil product guides, brochures, installation manuals and user guides simply enter your email address below.

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