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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. Existing 30A fused disconnect

  • The HVAC installer has asked for 240VAC 40A and 20A circuits. Each with a fused disconnect. Does that make sense due to the 80% rule? I don’t follow why a fused disconnect is required if the circuit has an HACR breaker at the panel. – Stanwood Jul 15 at 15:41
  • Can you post a photo of the existing compressor's nameplate please? – ThreePhaseEel Jul 15 at 15:42
  • I can. But I’m replacing the compressor. – Stanwood Jul 15 at 15:43
  • Can you provide us with make/model info for the new compressors then? – ThreePhaseEel Jul 15 at 15:44
  • @ThreePhaseEel just added these in. – Stanwood Jul 16 at 3:18
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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.

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    The min amperage quoted is 25A + 13.4A (not 15+15). Does this change your answer? Why is a nearby 120V recep required? – Stanwood Jul 15 at 15:38
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    From 2017 NEC: 210.63 Heating, Air-Conditioning, and Refrigeration Equipment Outlet. A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet shall be installed at an accessible location for the servicing of heating, air-conditioning, and refrigeration equipment. The receptacle shall be located on the same level and within 7.5 m (25 ft) of the heating, air-conditioning, and refrigeration equipment. The receptacle outlet shall not be connected to the load side of the equipment disconnecting means. – PhilippNagel Jul 15 at 15:40
  • @Stanwood Oh for some reason I thought you were describing the old unit and replacing with two of the mini-splits. – Harper - Reinstate Monica Jul 15 at 15:46
  • Thanks @PhilippNagel , this is so an HVAC tech can plug in equipment when servicing the compressor? – Stanwood Jul 15 at 23:51
  • Exactly, and probably so they can do so without using excessive lengths of extension cords. That's why it can't be connected to the load side, so there's power to it when the compressor is disconnected. They do have disconnects with Gfci receptacles built in by the way. – PhilippNagel Jul 16 at 0:01
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Keeping what you have You will need 2 home runs because the smaller unit has 20 a max.

I might do it with a single home run and install a nema 3r load center, this is one of the cases where small is ok, I think a 6 position 75 amp panel will do what you need. Including a 120v receptacle I don’t see one in the photo.

I don’t know if you will get away with the exposed UF outside that should have been in conduit as it was exposed. Below 8’

Run the small load center and pay the 12$ for the lockout devices and that can be your disconnecting means (I did this at my home) and this load center will have enough room to feed the 120v outlet. Look for spa load centers this is the style I have used for this same type of job.

Note the lockout devices must be permanently mounted and you need GFCI breakers make sure you get one that the breakers are not as much as the panel.

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  • The UF cables jumped out at me too. I've had many calls to correct stuff like that, mostly landscape lighting and sprinkler pumps put in by DIY'ers before this site existed.+1 – JACK Jul 14 at 22:27
  • The exposed UF is definitely getting fixed. I lean all manner of metal tools against the wall here and it has worried me for some time. – Stanwood Jul 15 at 11:21
  • GFCI breakers in my CH service panel are crazy expensive. I will hunt around for a spa panel and lockouts. Not sure it will be cheaper than another home run. – Stanwood Jul 16 at 3:49
  • You need a second disconnect and a 120v receptacle “within sight” these additional items usually make a small sub worth it. – Ed Beal Jul 16 at 13:29

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