We are arranging with an HVAC pro to replace our central AC compressor and add a separate mini-split system. We will have two compressors in close proximity on the side of the house where we presently have one. I'm trying to sort out what the outdoor electrical supply should look like.
The new units list the following requirements:
- Central Air: Rheem RA1642AJ1NB calls for 208-1-60 supply, 25.0A min amperage, 40A max protection (HACR breaker or fuse)
- Mini-split: Fujitsu AOU12RLFW1. The docs online are a bit fuzzy. An installation manual for (almost) the same PN calls for 208-1-60 supply, 13.4A min amperage, 15A max protection (HACR breaker or fuse). However, my HVAC pro said to provide 20A fused disconnect)
Presently I have a 30A 240VAC fuseable pullout switch (Eaton DPF221R) fed by a 30A breaker in my service panel. My contractor quoted $250 to replace the outside disconnect. Separately, he requested a 240V 20A supply for the mini-split.
Based on answers so far I’m leaning towards a #6 home run on a 2-pole 50A breaker to the existing interior junction box. From there I would run in conduit to two outdoor disconnects: the existing 30A fused disconnect (with 20A fuses) for the mini split and a new 60A fused disconnect with gfci outlet (and 40A fuses) for the central air.
The existing disconnect is in good order but the exposed UF will need to be corrected.
Best Answer
You must use equipment which is Approved (NEC 110.2). Approved, in practice, means having an independent NRTL (such as UL) approve that the appliance did in fact follow design standards. Part of approving the appliance is approving the instructions, which you must follow. (NEC 110.3(B). If you are installing non-approved equipment, all bets are off.
However, approved instructions override Code generally. So if the instructions call out a 15A maximum overcurrent protection, then this has been reviewed by the manufacturer and by the NRTL both, as correct. That is the bottom line.
It sounds like the big unit needs at least a 35A breaker. They don’t make those, so you’ll have to do with a 40, as per their instructions. The mini-split needs - well, I would’ve said a 20, but the instructions say 15 max, so that’s the last word on the subject.
So (25+13.4) * 125% = 48A you need to provision, so #6 (or #8 THWN in conduit) will suffice, with a 50A breaker in the main.
Normally I hate outdoor subpanels. The reason I like this one is it doubles as the appliance disconnects for the A/C units.
You could also use the subpanel for anything else you please: an RV stand, an extra bedroom circuit, EVSE charger, the mandatory repairman’s outlet which must be within 25’ of the A/C units, etc. It would need to be fed and sized accordingly.
The other way to achieve the disconnect requirement is to run separate branch circuits to each device (8 AWG to the big one, 14 AWG to the small one) and install a listed, non-removable locking device on each of the breakers. This allows the A/C repairman to do lockout/tagout at the panel, in lieu of having a disconnect within line-of-sight.