Hello,
We are trying to install two Nest Gen4 thermostats in a two zone system. The prior thermostats only used 4 wires (Red, White, Green, Yellow) but there is a 5th blue wire available in the line up to the control board. The control board itself has terminal locations for only the four wires on each zone (Red, White, Green, Yellow).
Is there somewhere else on the board I could connect the Blue (Common) wire to? I have found the line in terminals (24R and 24C) on the board and can read 28v between them. When I connected the common to the 24C terminal on the board the light on the Nest Connection plate came on, but the setup app still said that a C Wire needed to be connected.
Connecting to the 24R terminal doesn't seem right, but I wanted to ask here before proceeding further.
