My weather compensated Viessmann system boiler - quite old now - seems
happy enough to heat the water above 60c at all times, but modulates down
when driving the heating to the most economical temperature once the house
is up to the set temperature.

I have heating to get the house to the right temperature as quickly as
possible, rather than to save money.

Would likely be different with underfloor heating left on 24/7.

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*Change is inevitable, except from a vending machine.

Dave Plowman London SW
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