Question about wiring minisplits — electrician’s mistake
I consulted with the electrician before he ran the wiring for our new home. I knew that mini splits weren’t something they would see everyday, so I wanted to make sure everyone was on the same page. We noted that the unit needed three wires plus the ground, and everyone knew what that meant because I had to run to Lowes to pick up some extra 12/3 wire since they were running low.
Fast forward a couple weeks, and the drywall is up and the HVAC guys are starting to hook things up. Turns out, the electrician only ran 12/2 to the units. However, the HVAC guy ran some thermostat wire from the outdoor unit to the indoor unit.
Can the thermostat wire serve as the ground connection between the two units? What is the purpose of the extra ground wire?