Need help with installing Honeywell voice controlled thermostat, which requires 4 wires my current one has only 3 wires, live, neutral and common Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

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I am planning to replace my room thermostat with HONEYWELL voice controlled wifi thermostat which requires 4 wires, but three are only 3 wires , live, neutral and common coming into the wall box where the current thermostat ( Heatmiser DT ) is the 4th wire that is is needed is to run from Honeywell thermostat to boiler. My question where in the boiler or programmer ( Draytion lifestyle LP 522 ) should I connect it. Any advice will be appreciated.,