Martin Angove wrote:
In message . com,
wrote:

than a system with 2 or 3 degrees of hysteresis. All past advice
on
this
group seems to point to the fact that boilers are most efficient
when
they run for long periods, and least efficient when they short
cycle
on
and off.

why is that?

In terms of heat loss thru walls etc, a more costant temp will lose
less heat, so the q remains how the boiler efficiency will affect
it.

The difference in heat loss between (say) 19C +/- 0.25C and 19C +/-
2C
can't be that great, surely? Intuition implies it should be exactly
the
same, though I doubt it is in practice.

Humans set room temps according to whats comfortable. If eg 19C is
comfortable, you can either set it to 19.25 +/- .25 or 20 +/- 1. Hence
bimetals will lose more heat for the same comfort level, as the same
comfort level requires higher ave temp.


My question was about boiler
running times. Received wisdom seems to be that running the boiler
for 5
or 10 minutes repeated every 15 to "top up" the heat is going to be
less
efficient than running it for a solid 30 minutes every hour.

on what basis do you think its less efficient? Im not aware of any
mechanism that would make it so.


NT