Gas Heat Recovery System and devices

Also known as Passive Flue Gas Heat Recovery System is a system that captures and re-uses the heat wasted by a boiler. Any heating system that burns a fuel (such as oil, gas and wood) to create heat, wastes as much as 20% of the heat in the process. This wasted heat is dispersed of through a Flue.


A traditional boiler will see the flue gas reach temperatures of as much as 180 degrees Celsius and this is disposed of through a vapour in the flue.

A Flue Gas Heat Recovery System captures this wasted heat and uses it to heat the incoming water supply. By doing so it can reduce Domestic Hot Water requirements by as much as 50% in winter (when the boiler is used more often) and by as much as 20% on an annual basis. Flue gas Heat Recovery systems are also an eligible measure under the Green Deal Initiative and can provide a cashback return. We sell a range of Passive Flue Gas Recovery Systems and Devices either as a standalone energy saving measure or as part of a whole house system. We offer a complete home energy and heating management package. This is where we can install mechanical-ventilation-heat-recovery MVHR, your hot water all of your electrics,underfloor heating and integrate them using inbuilt management systems allowing you to control your house according to your own service requirements and functionality. We can guarantee that we choose the correct renewable technologies designed for your needs that will save you money. We pride ourselves on our strong customer care and have the technical expertise to deal with the most complex of self build andcommercial projects

The following information provides more details on Flue Gas Heat Recovery Systems in particular. If you want to find out more about the types of devices we sell, our energy and heating Package or anything else here Give us a call on 01223 852267, drop us a line via our Ask the Experts tab or contact us.

Before the flue gas can be used to heat the incoming water supply, it must be turned back into a condensate liquid so that it can pass through the heat exchanger. This is done in condensing boilers which use a fan to cool the flue gas and thereby deliberately cause the flue gas vapour to turn into a condensation.

This condensation is then pushed through the heat exchanger to heat the incoming water supply. In the process the flue gas goes from 180 degrees Celsius to approximately 55 degrees Celsius. The condensation that comes out of the heat exchanger is slightly acidic and therefore must be disposed of through a soak-away. This is why you will see soak-away pipes on condensing boilers.


Flue Gas Heat recovery systems can be built into the boiler (as above) or come as separate systems that fit onto the existing boiler. The basic workings of a separate unit are shown below, although these are the same for an in-built integral unit:


This separate unit will fit above or below the existing boiler:


Most modern boilers are now Condensing boilers and these already incorporate Flue Gas Heat recovery Systems:


A traditional boiler is only around 80% efficient and with a Flue Gas Heat Recovery system they can reach efficiency levels of 95%. The paybacks can be as low as 5 to 7 years, with individual units costing around £600 excluding installation.

Estimated Cost £600
Estimated Annual Payback £100
Estimated Payback Period 6 years