Condensing boilers, a brief look at the benefits you can gain when you install a new condensing boiler.
If your whole boiler has to be replaced then you will have very little choice other than to install a condensing boiler, the gas boiler regulations currently stipulate this in 99% of cases. Being forced to install a condensing boiler is not a major problem has they are very energy efficient and should help to lower your heating bills over their active life time.
A condensing boiler is and efficient, innovative boiler design that contains an additional heat exchanger in order that the hot exhaust gases transfer most of their energy to pre warm the water in the boiler system. When operating at high efficiency, the water vapour developed in the burning action distils back into a liquid releasing the heat that was in the water vapour into the heat exchanger. More on what happens to that heat later.
A subsequent requirement will be that this water, named condensate will need to be piped outside to a waste pipe or water drain. There are no stringent requirements for this, merely that the water can flow away rather than accumulating with the boiler. If for some reason the pipe becomes blocked or frozen the accumulation of water within the boiler will trigger a sensor with it and stop it working until the blockage is cleared.
The boiler should be mounted to a wall and the exhaust gases will travel through the flue. Your boiler installer needs to take care with the positioning of this flue to ensure that nearby properties or passers-by are not impacted by the exhaust plume.
Hot water is initially served by a modest water holding tank to enable quick hot water availability.
The large heat exchanger which has absorbed the heat from the waste gases is then used to pre-warm cold water entering the boiler reducing the amount of energy required to bring it up to the correct operating temperature.
Can someone advise on the right boiler size?
Getting the right size boiler is important in achieving the efficiency levels as designed in the condensing boiler. It was a past practice to install oversized boilers. Although this ensured that there was little chance of the boiler falling short on its requirements, without any concern for icy weather, it also meant that they were principally working at a reduced capacity, and so working under their designed optimum efficiency. If you have fitted additional loft or cavity wall insulating material since the current boiler was fitted in your house, it is highly likely that you will be able to fit a lower capacity boiler than before.
Before you get a new boiler we advocate you get advice from a CORGI registered installer.
If I fit a condensing boiler should I fit large radiators?
The main efficiency benefit from a condensing boiler is that it has an oversized heat exchanger. Bigger radiators would allow lower return temperatures, and so result in even better energy performance, but the additional saving is not shown to be cost effective, keeping in mind that the system is running at very low capacity for the majority of the heating season. Whilst this assertion is correct householders would plausibly accept this in smaller properties.
The process we have discussed was incorporated in the terms of reference for the SEDBUK project, and had a look at the recommendations for condensing boilers. The determination was that they need not, and the test results for both types share the same SEDBUK computation.
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