heatmiser PRT/HW

[Andy Burns]

I'm thinking of using a Heatmiser PRT/HW programmable stat

either in addition to (or as a full replacement of) my existing programmable controller (it's LCD display having died)

All their wiring diagrams show the use of a motorised valve to control h/w and c/h, but my system is gravity h/w and pumped c/h, I phoned them and they were less than convincing that the PRT/HW could entirely replace the existing controller, I wonder if I can do it using an external SPST/CO relay to negate the c/h pump supply when h/w output is switched on? I'll probably email their tech dept to see if that elicits a better response, but anyone here already done it or think/know if it can work with or without a relay? Can I still incorporate a h/w tank stat too?

TIA ...

[Andy Burns]

Thinking about it, I don't want to negate anything, just drive the c/h pump direct from the stat's c/h contacts, and the boiler via a relay from the c/h contacts OR'ed with the pump circuit, is that sensible?