Heatmiser PRT Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[MontyWB]

Anyone know how to replace a 25 year old thermostat with a digital one with regard to wiring? I have red, blue and yellow wires to current thermostat and I think I have to connect live to L and A1, neutral to N and yellow to A2 on the PRT. Am I correct?

[plumbbob]

You haven't said what model of new stat you have so it is difficult to be precise. Generally on new thermostats the neutral (usually the blue wire) is unused and must not be connected otherwise there will be a big bang.

See this topic

https://www.diydoctor.org.uk/forums/view ... hp?t=14932

[MontyWB]

Hi Bob

It's a Heatmiser DT / PRT.

I think I have to connect live to L and A1, neutral to N and yellow to A2 on the PRT.

That's how it looks to me from the wiring diagram.

[plumbbob]

Yes, looking at it now, you are right. PRT's need the neutral. I thought it was just a standard thermostat and the new digital ones don't use the neutral.