Does the earth need to go anywhere? Does it matter than the heat link is downstairs and the boiler upstairs? The manual recommends it's placed near the junction box. I could trace the wires back to the junction box I guess.
All,
I have recently purchased the Nest Thermostat with Heat Link and looking to replace my existing Honeywell T6360B. This thermostat is on the ground floor (lounge) and the boiler upstairs in the bedroom (combi boiler)
My Honeywell T6360B is wired as follows...