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?
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.