On 11/01/2019 22:42, wrote:
On Friday, 11 January 2019 18:54:03 UTC, 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

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

I tried to explain this but was met with

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

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

tim

The only realistic answer is to run it as hot as is necessary to
provide enough heating. Cooler means more boiler efficiency, hotter
means more rad output. The required target temp varies from one house
& install to another, and varies with the weather.

yup, spot on.

It leaves three options:

set and forget - chose a high flow temp that meets the worst case, and
accept that you will be running with less efficiency / comfort for most
of the year.

manual - adjust the flow temperature yourself in response to
particularly cold days - probably works quite well for users who are
clued up enough to understand the requirement.

automatic - use weather compensation to "close the loop".


--
Cheers,

John.

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