I know this is a variation on a well worn theme so apologies in advance. I need to wire in a Honeywell Dt90e thermostat which is a 2 wire thermostat but the sundial wiring centre has 4 connections numbered 1 to 3 and earth so not sure which ones to connect to. The system is C plan gravity HW pumped CH and has a Tempus Seven contoller.
Thanks
Thanks