I use Nest for heat only (hot water radiators) distributed over 3 separate zones. I already have Nest thermostats in 2 of 3 zones, working perfectly.
I am trying to install a new Nest on the 3rd zone. The existing thermostat (LuxPro) is functional. The old unit is connected with 2 cables (Rh and W - there is a jumper wire between Rh and Rc). This suggests (to me) that the existing wiring (while dated) provides power to the thermostat. HOWEVER, when I connect the Nest, I am getting a wiring error (no power to the RH terminal) and the thermostat shuts down. Of interest, when I connect the unit to the back plat, a signal is sent to my heating system and zone turns on (before I am able to complete the installation of the new thermostat.... Strange.
1 - Why does the old unit get power but Nest generates a wiring error?
2 - Do I need more than 2 wires to have the Nest function properly? Replacing the thermostat wire is basically impossible in this location...
3 - Is there a fix for this?
Thanks
