"mike ring" wrote in message
52.50...
"Clive M" wrote in
:

Does anyone have a diagram of how a system with 2 pumps and no valves
is wired together to give interlock? Secondly how does pump overrun
work if 2 pumps are used (i assume you have to dump into the CH
cylinder)

I've considered the Grundfos Pump Plan - seems very advantageously priced
at plumbworld ATM, and came up with this doc

UPP_Pump_Plan_05_03.pdf

but I don't know where from.

It contains a wiring diagram.

I think they also sell a complete control pack, which I would be tempted
to
use if I were installing it.

I really like the idea, but it's a bit bleeding edge for me...., what
happens if one pump fails in a cold snap?

What happens if a zone valve packs up?