In message
, NT
writes
On Oct 23, 1:07*pm, fred wrote:
In article
, NT
writes

On Oct 22, 6:50*pm, fred wrote:
In article , chris French
writes

In message
,
NT

100% at 12p/unit versus gas with maybe 85% efficient at 3-4p/unit.

I doubt a gas boiler keeping one rad warm gets anywhere near that.

Agreed, assuming a 1kW rad in a small room even a modulating boiler will
be short cycling its arse off every few minutes, warming up the boiler
and pipes with all that doing to waste.

It could work nicely with a thermal store system but not everyone has
one of those and fewer still have the circuits separated enough to
permit this kind of operation.

Even if 50% of the heat is lost in the pipework to the rest of the
house, most of that heat is saved come evening time. So efficiency is
still fairly high.

The whole object is to avoid heating the rest of the house.

I think the object is to pick the cheapest to run system

Why would
this waste heat hang around until the evening? I expect the energy will
have dispersed to the ether long before then.

If you heat a house to 20 in the morning, and leave the system off
till 6pm, a good 80% of that heat is still retained indoors by then.

Either way I don't see that as the main issue, I view it as bad practice
to design a system that will repeatedly short cycle a boiler. I designed
my system for a long slow burn to avoid the thermal stresses that
repeated cycling inevitably brings and I hope to reap the benefits of
this in a longer system life.

Is thermal cycling a major failure mode in boilers? I didnt think it
was.

Only really as far as relay contacts switching inductive loads and that
sort of thing is concerned.

Otherwise natural built in obsolescence will take its toll before other
factors



--
geoff