"Tony Bryer" wrote in message
...
In article , Rory wrote:
Thanks for your ideas - I'm slightly baffled as to how the
pipe stat would be wired to the pump. I can see how it would
stop the pump as the flow temp dropped below (say) 65C, but
how do I get the pump to start when the system is cold and the
stat contacts would be open?

The pipe stat will have n/o and n/c contacts. Common goes to pump,
n/c to boiler call, n/o to permanent live. Boiler switches on and
pump runs. When the set temp is reached the stat switches over and
the pump keeps running until the system cools down.

This will momentarily de-energise the pump as the stat switches over from a
switched live to a permanent live. This is what he doesn't want as it
effects the pump operation.

It is best to have the switched live energise the pump as per normal. Then
a permanent live through the stat to the pump. When cold the switched live
switches on the pump. The flow gets over 65C and the stat switches in the
permanent live to the pump too. It doesn't matter as the pump is already
energised. The switched live de-energises, but the stat is still above 65C
so the permanent live keeps the pump energised and running until the flow is
cooled. Simple.