Central Heating Gas Boilers

10 Mar 2008
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United Kingdom
We have a worcester bosch 24 sbi system boiler about 8 years old.Looking to replace it with a worcester bosch greenstar 30cdi system as it doesn`t
seem to give enough heat in our 5 bedroom house with 13 radiators.
We also have a megaflow cylinder with no tank in loft.
Are there better boilers and what would be a good price to make our house warm and comfortable.
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There are plenty of other reasons why your rads might not be getting up to temperature.

Has your current boiler ever succeeded in getting all your radiators piping hot ? If it's performance has deteriated, then it could point to other problems - sludge in the pipework and radiators, faulty TRVs, lockshield valves and/or room thermostat, adequate gas supply etc

As for getting a comfortable temperature in your house, do you have double glazing ? Cavity wall insulation ? Plenty of loft insulation ?

These can all make a big difference to how warm a house feels and also how well it retains the heat that you put into it.
For reference, I live in a 4-bedroom detached house with 15 radiators and my WB 37CDi combi puts out 9.8 - 30kW to the CH.

I can't remember the exact figure, but the total required to heat all the radiators was somewhere around the 20kW region.

The total figure for your house will obviously vary depending on the size of your radiators but if you have large rooms and therefore large radiators, then I guess there's a chance that, at 24kW, you could be pushing the upper limit of what your boiler will be capable of.

If your radiators are fairly standard sizes and styles, then it should be possible to work out the kW ratings with a comparable Stelrad/Myson design (see their website brochures for the figures).

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