


Which one is the C terminal?
I’m installing a smart thermostat for a friends business but the Control wire is not hooked up to the hvac unit. Can someone tell me which terminal to hook it to?
The third picture is a diagram I drew so I could tell what was happening. One of the brown cables goes to power, one goes to the thermostat, the third is just loose in the ceiling and not hooked to anything.
Update: I guess this is the alarm system. I’ll have to come back tomorrow and get on the roof to find the air handler and try to hook up the control wire.