How do I correctly wire the thermostat in my 100-year-old restaurant building with unconventional HVAC coding?
Asked by Carter Hayes 
3 months ago
Last Updated: June 15, 2024
Hey, so I have this restaurant in an old building, like over 100 years old. We were trying to update the thermostat yesterday but unfortunately, the air conditioning is still not working. The wires are a bit confusing, not following the usual HVAC coding. There are 2 black wires, 1 red wire, 1 yellow wire, 1 red/white wire, and 1 yellow/white wire. I’m a bit lost on which wires should be connected to what in the wiring harness.
You should contact a heating and air company. They will be able to assist you.
If you didn’t snap a photo before dismantling it, you’ll need to either A) trace the wires to their end points or B) contact an HVAC technician for assistance.
If you forgot to label the wires, I would recommend pausing and getting a professional to help trace them.
Hey, did you remember to turn off the air handler before disconnecting the thermostat?
It’s all sorted out now, the HVAC technician came to take a look. The installer had one of the wires connected incorrectly, and it turns out the new thermostat we purchased was faulty.