In an earlier contribution to this discussion,
Tom wrote:

But if the pipeology is cold to start with how will the pump ever
get to know when to start?


I described a method of doing it in a post a couple of days ago. The
pipe stat needs to have change-over contacts. The one which connects
when the pipe is cold is connected to the boiler's switched live.
The one which connects when the pipe is hot is connected to
permanent live. Common is connected to the pump. So:
* Cold Pipe: the pump runs whenever the boiler receives a heat demand
* Hot Pipe: the pump runs until the pipe cools down

Simple, eh?
--
Cheers,
Set Square

I see, hmm, that's very elegant, I like it.
The pipe stat would have to be very reliable,
any recommendations?
There would be a very tiny (millisecond?) break in the power to the
pump as it changed over (break before make), but I don't suppose it
would affect the pump as it's an inductive load and the back emf
would take care of that or am I talking cobblers here as I dredge the
depths of my school boy memories [50 yrs ago, :-(. ]
Many Thanks
Tom

Well, it's no different from the way in which the pump over-run stat works
in my Baxi boiler - and the pump doesn't mind that!
--
Cheers,
Set Square
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