I recently decided to take the plunge, sell a pint of blood, and purchase a Nest Learning Thermostat.
My system is set up as follows...
- AC controlled by Unico system in attic (Rc-Y-G)
- Heat controlled by Taco ZVC404-4 in basement (Rh-W)
The issue is the Nest seems to struggling to pull power from my Taco. (Error on my Nest reads = N72 : No power to the Rh wire). When the heat zone is not active, the orange T-Stat call light flickers and is not solid. When the zone is active, is stays solid and eventually the valve opens.
I did not orignally have a c-wire installed, so I ran one from my Unico unit in the attic to the Nest, thinking that this would solve my problem, but the flickering orange light on my Taco persists.
Does the c-wire need to be wired to the Taco panel instead of the Unico? Or is this an issue with my Rh wire?
Pictures of both of my valve panels are attached.
Any words of wisdom would be much appreciated!