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tim... tim... is offline
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Default how hot do you run you CH boiler



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On 11/01/2019 21:30, John Rumm wrote:
On 11/01/2019 18:52, tim... wrote:
I had a new Combi fitted today (in the to-be-moved-to house).

Fitters told me that I should run this at 74 degrees.

Which I thought far too high, as


Indeed...

1) it makes the radiators too hot to touch
2) basic thermodynamics suggest that a better temperature profile will
result from having the radiators at the lower temperate for longer
period than a higher temperature for a shorter period


It might be required in particularly cold weather, but most of the time
you will be able to use less.


I tried to explain this but was met with

"The recommended temperature is required for the condenser to have any
effect"


You will most heat recovered from the condenser when the return
temperature is below about 54 degrees (the dew point of the flue gasses).

and the completely bogus "the temperature of the water in the radiators
is set by the TRVs not the boiler temp. I couldn't persuade the guy
that he was taking bollox, he played the "I'm the experience heating
engineer card and I know better than you" card. ****

Anyhow, at my current house it is 55 and works perfectly well

what do you guys/galls do


I have weather compensation on mine, and so it chooses its own
temperature based on the outside temp. Basically that means its runs as
cool as it thinks it can get away with and still be able to reach the
target set point temperature in a reasonable amount of time. (the
relationship is set by choosing a mapping curve that reflects the rate of
heat loss of the building).

Currently the external temp is 6.5 deg C, and the flow temp is running at
54 deg. If it were to go well below 0, then it might push the flow temp
up into the 70s. When its milder it might run flow temps down in the 40s.


I thought the advice was to heat DHW to 60 degrees to avoid the risk of
legionella, and that's not going to happen if the boiler's running at a
lower temp.


the temp for the hot water and CH system are set independently in a combi