A condensing boiler review

A condensing boiler is a high efficiency modern boiler that incorporates an additional heat exchanger in order that the red-hot waste gases transfer much of their heat to pre warm the water in the boiler system. When running at a good efficiency, the water steam produced in the burning process turns revert back into water loosing the latent heat of vaporisation.

A consequence is that this liquid, called condensate, most times acidic, needs to be piped outside to a drain or soak away. The boiler should be fitted against a wall and the output fumes will pass through the flue. Hot water is initialy served by a small recepticle tank to enable convenient and rapid hot water availability.

Can you advise on the right boiler size?

It was a past practice to install outsize boilers. Whilst this ensured that there was no possibility of the boiler being unable to furnish sufficient hot water, even in the coldest winters, it also meant that they were only employing a part of their heat generation capabilities, and so running in an ineffective mode. If you have improved the energy efficiency of your household since the last boiler was fitted, it could well be that you will be commended to install a smaller boiler than before.

We advocate looking for professional advice from a CORGI registered installer before selecting a suitable substitute boiler.

Do I need to set up outsize radiators with condensing boilers??

The underlying reason for this amended efficiency from a condensing boiler is because it comprises a bigger heat exchanger. Bigger radiators would result in cooler return water temperatures, and so result in even better energy performance, but the extra economies suffer from falling returns, as you should count the fact that that the system is running at very low capacity for the majority of the heating season. That in all probability remains true, though the reduced heating requirement for new build may well mean that homeowners would now allow over-sized radiators more willingly.

The SEDBUK project looked at this, during which it was considered whether condensing boilers required to be treated differently from others. The outcome was that no new recommendations were required, and the test results forall the boiler types share the same SEDBUK computation.