DIY Doctor

condensation after having a new boiler fitted

Postby mc010e2303 » Tue Dec 01, 2009 9:20 pm

i had a new combi boiler fitted earlier this year ,now having a lot of condensation .how do i stop this ?never had this problem with my old boiler which was 20years old could anyone tell me if there is a connection and advise me how tofix it ?Ialso have double glazing :( :(
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Simply Build It

Postby acsimpson » Wed Dec 02, 2009 10:52 am

I'm no expert but a new boiler should vent all it's fumes outside, and I think bring it's own fresh air in. Is the problem only in this room or does it affect other rooms? Could it be caused by the house being warmer and so holding more moisture which then condenses on the windows?
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Postby Perry525 » Mon Dec 07, 2009 8:27 pm

It is unlikely that a new balanced flue combi will have anything to do with condensation.
Condensation is due entirely to a drop in temperature.
Warm air holds up to 30 grams of water vapour per cubic metre.
Cold air holds none.
When warm saturated air meets a cold surface, its temperature drops and the water held in suspension condenses onto the nearest cold surface.
The solution is simple keep the temperature steady and the water vapour remains in the air.
Except when it is cold outside and the temperatures of your windows drops- then if there is a lack of circulation in the room, ie; you close the curtains trapping cold air in the recess then the water vapour will condense as the air temperature drops.
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Postby slapdash » Thu Jan 07, 2010 10:51 am

I noted this problem too - our utility room used to be the warmest room in the house thanks to the dodgy old boiler. it was so inefficient that the amount of heat radiated from it - rather than pumped into the hot water system - kept the utility room toasty. now however with the shiny new class a combi boiler all the heat goes into the hot water / radiator system, the utility room is freezing (!!) and we get condensation that wasn't there before.
The wife hates it! i just tell her to put her coat on when she's doing the ironing (and shut that door!).

So your condensation could just be a result of lower temperatures in that room. I guess we'll have to put a radiator now into the utility room. :roll:
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Postby Perry525 » Fri Jan 08, 2010 3:43 pm

Interesting that, you buy a new boiler to save money on the gas used then, have to spend more money fitting a new radiator to heat the room. Nice!
I would be interested to hear is a few months time how it works out for you, if indeed you do save money on gas used.
The so called efficiency you pay for is basically not having a pilot light and recirculating the heat from the burnt gas to preheat the circulating returned hot water.
However, this only works while the system is heating up, once all the pipes and rads are warm the returning hot water has little to gain from the burnt gas and the advantage is zero.
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