I swapped out a 24v Honeywell Thermostat for a NEST Thermostat. I followed the Manufacturer instructions for install. Everything was working for a week or so. I recieved an error(pictured below) regarding the Y1. NEST indicated I must need a "C" Common Wire run from the air handler.
Can I Tap any of the wires, going to the outdoor unit?
Blue/ Brown- Going to TACO sr503 controller
Yellow/Green/ White /Red- Going to NEST
GREY SHEATHED (Not Pictured) – Going to Outdoor Unit
Best Answer
According to that wiring diagram, C is not available on the terminal block for the thermostat and outdoor unit. You'll have to find it by locating the 24V transformer. According to the wiring diagram, the yellow wire on the transformer would be C. You can verify that it is the correct wire because it should be connected to a couple of relays, and the other wire coming off the transformer should be red and connected to the terminal block for the thermostat.