An AC-only machine cools a storage facility: no heat. The 30 year old thermostat is to be replaced with a wifi thermostat, which requires a C-wire to power the electronics.
There are 4 wires:
- Red (28V)
- White (?)
- Green (fan)
- Yellow (Cooling)
Convention indicates white is to for calling heat: that being said there is no heater.
- Why is it connected to the thermostat, if the machine is AC only?
The potential difference between the white and the red is 28V:
- Can said potential difference power the wifi thermostat (can WHITE serve as the C-Wire)?
I traced the thermostat wiring back to the machine and snapped a photo:
A second identical wire connects the indoor unit with the outdoor unit. It seems that both blue wires are connected to the machine's blue leads. Now I am wondering if I can rely on the convention of blue to serve as the C-wire.