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Post by 25 quid on Sept 13, 2022 10:14:26 GMT
There's been lots of talk about this recently, e.g. energyguide.org.uk/boiler-flow-temperature/But definitely a big win if your radiators are big enough and your house insulated enough to not mean it takes hours to warm the place. So, turn down the flow temperature so your return temperature is chilly enough to cool the hot combustion gases enough to extract all that lovely extra heat of vaporisation... |
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Post by gerryhatrick on Sept 14, 2022 8:28:16 GMT
Most boiler installers (I understand over 95%) never configure the boiler properly after installation as they don’t know how nor the reasons therefor. They leave them on the default settings which are often wrong and won’t enable the boiler to achieve the 90% efficiency it is meant to have. A flow temperature of 70 C is more than adequate and it means a return temperature of 50 C or less and thus the boiler condenses as it should. At high temperatures it does not condense. Efficiency drops. I have my flow temperature set to 65 C which is fine. I have tried it at 60 C but it takes longer to warm a room up.
Not only the flow temperature needs properly setting but also the power rating of the boiler. Many are left at or above 20 kW which is too high. Reduce it to the minimum. Mine is 6.8kW and works fine at that level.
At these settings, when my boiler was serviced some months ago it showed 99% efficiency.
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Post by 25 quid on Sept 17, 2022 8:29:11 GMT
How does the kW rating setting work? Does it just limit the maximum output? I'd have thought that as the boiler nears its set-point the modulated valve would turn it down anyway.
Might perhaps increasing the maximum power but further reducing the flow temperature be more efficient — and warm you up faster? i.e. efficiently dump loads of heat into a cold system, but then limit the max flow temp to maximise condensing efficiency?
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Post by gerryhatrick on Sept 17, 2022 8:49:36 GMT
I thought the same as you. If it is up to temperature it cuts out. But I understand if set to high it will burn at that rate regardless which is an excess burn. Reducing it the job is done just as well but with less gas consumption. I think it’s Veissmann have a boiler that goes down to around 3 kW.
I have noticed little difference reducing the flow temperature to 65 from 70. Rooms still warm up quickly. But dropping it to 60c it is slower. Not that much slower though. I might just discreetly drop it to 60 and not tell anybody! Some only feel the cold once you tell them the setting or that the heating is off. If you don’t tell them they don’t complain. A cheap way of saving cost!
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Post by Duppy on Sept 17, 2022 10:48:15 GMT
I think it was gwyndy that suggested reducing the power output of the boiler. After research I managed to reduce mine, it was set at the maximum 28kw, I reduced it to 10, it didn't make any difference in temperature but my bills did reduce somewhat I've got a notebook somewhere where I recorded the readings, and I noted the date I made the change. Unfortunately since moving I can't find it. |
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