my parents' cape in hamilton is getting a 3-zone mini-split next month and the hvac company said "you'll need an electrician for the power." my dad looked at me because I'm in the electrical program at vo-tech, which, no, I'm a student. but I want to understand what the electrician is actually going to do so I can watch and not be useless. like how do they know what size breaker, what's the box on the wall outside for, and does it need a GFCI? our book says something about outdoor GFCI but my teacher said it's complicated
HVAC contractor, owner · 25 years · Middlesex County, NJ
Mentor
From the HVAC side, also watch the interconnect between the outdoor unit and the heads. Most multi-zone units power the heads from the outdoor unit through that cable, and the manual specifies the wire. Nobody should be using leftover thermostat wire for it.
Electrical inspector (former contractor) · 26 years · Ocean County, NJ
Mentor
Your teacher's right that it's complicated. Here's the outline. Wire and breaker size come from the outdoor unit's nameplate: the minimum circuit ampacity sets the wire, the maximum overcurrent protection sets the largest breaker allowed. The box outside is the disconnect, which the code wants within sight of the unit so a tech can kill it while working on it.
The GFCI part: a recent code edition expanded GFCI requirements for outdoor outlets in a way that caught HVAC equipment, a lot of inverter units nuisance tripped, and there were changes and local amendments afterward. Check which code edition is in effect for your parents' permit. That's a question for the inspector, not the internet.
Watch where the condensate from each head goes too. Not electrical, but my uncle got called to a Cape where a head was draining into the wall cavity lol