On 14/01/2016 12:34, Harry Bloomfield wrote:
Has anyone got any thoughts on the correct setting for the temperature
dial on a condensing boiler please?

Its only marked MAX and MIN and has always been left on MAX since it was
installed a few years ago. Our HW stat is on 80C, because that is what I
want. Set the boiler output temperature too low and it will constantly
cycle on and off unable to achieve the demand.

Suggestions and your reasoning please?

Generally the lowest flow temperature that you can get away with, and
still achieve adequate heating and fast enough warm up, is the ideal. It
will result in the lowest return temperature and the greatest condensing
efficiency. As side benefits it also gives less creaks, clanks, and
groans from the metalwork of the radiators and pipes since there is less
temperature swing. Less "danger" from hot rads etc.

However the general problem with this approach is that on cold / high
heat loss days you may not be able to achieve the set temperature in the
house, and it poses a problem if you want to heat a cylinder to a high
temperature as in the case here.

The solution to this problem is via a system that supports split
temperature operation, (i.e. one that understands the difference between
running rads and heating a cylinder and uses a higher flow temp for the
the latter). The posh version being weather compensation, that also
understands when its cold outside and makes further adjustments to the
radiator flow temperature in response.

Not all boilers have the controls to do these things.


--
Cheers,

John.

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