Room thermostat problem/replacement

[littonlad]

Hi, wondered if I could get some advice.

I've changed an old Proscon mechanical room stat as it was on the blink (needed the dial wiggling round to make the rads get hot) for a Drayton RTS8 a la Screwfix.

It's a Baxi back boiler and the wiring to the stat is a flat twin and earth with 240V across the live and neutral and a separate red wire which I think is the demand wire from the boiler.

Connecting it up in 3-wire configuration as per the instructions doesn't work. Everything looks ok but the boiler comes on then goes off again.

So I'm back to wiggling the Proscon dial......

Any suggestions most welcome.

 

[MANDATE]

I assume your four wires are:
(a)A 'live' from programmer. going into terminal 'L'
(b)A 'switched live' that goes to the boiler/pump, this going into terminal 3
(c)A neutral wire normally 'blue' going into terminal 'N'
(d)A earth wire normally green/yellow. This not required but if any existing earths need to be joined terminal is provided.

I think its a matter of proving which wire is which. a meter from earth to the other wires will only show voltage from the 'Live'

 

[littonlad]

Thanks for that Mandate, using a multimeter I've proven that the new stat is faulty.