In message l.net, at
13:12:54 on Fri, 9 Oct 2020, Dave Liquorice
remarked:
On Fri, 9 Oct 2020 06:39:27 +0100, Roland Perry wrote:

Wouldn't put the stat in a room with a heat source it's not
controlling. Wood burner makes living room nice and warm, stat
is
satisfied and rest of house doesn't get any heat.

But I'm not in any of the rest of the house, Dear Liza.

*Any* heat, even if it's blowing a gale and -10 C outside...

Remember with your current short cycling, if a room cools bit that
radiators thermostatic valve opens a bit and warms the room. With
the
room stat satisfied this won't happen as the boiler is forced off.

It's a small enough house that heat percolates around it even when room
rads are off.

Fairy Nuff.

... however if the room stat simply switches off the boiler like a timer
would, does the circulating pump stop, ...

The pump more or less goes off with the bolier. It'll probably have
built in overun to remove residual heat from the heat exchanger to
stop it overheating.

... and does in effect turning the boiler on and off several times an
hour have any undesirable other side effects.

er, the short cycling is almost ceratinly fireing up and shutting
down the boiler far more often than it will once a room stat has
control.

I'm not sure I could find a separate connection to make to the boiler to
switch it by a thermostat rather than the timer. The timer just has one
2-core connection to the boiler, plus its mains power.

Not experienced with modern boilers but the KISS principle applies,
plumbers are not electricians... So I'd expect at a minimum a
terminal block with positions for permenant L,N,E (from a SFCU) and
L,N,E,Sw L for connection to external time switch/thermostas etc. If
there is a built in time switch I'd expect a "SW L out" (from time
switch) and "SW L in" from external controls. By default the L and SW
L would be jumpered togther, like wise the "Sw L out" and "Sw L in".

I'll post a diagram of the status quo shortly.
--
Roland Perry