I'm installing the mini split and wiring it to the disconnect they had for a spa which is now long gone.

They wired a 110 gfci off the disconnect which I'm not touching.

Coming in from the main panel is a 3 wire line, black, red and neutral.

The neutral is connected together at the neutral bar in the box, the ground for the GFCI is connected to a screw to the box. My mini split only asks for 2 hot wires and a ground. Should the ground go to the neutral? Picture of the box attached.enter image description here

The yellow on the left is the new wiring, the black on the left is the gfci and the right is the line in.

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    Can you post photos of the labeling on the disconnect box? I can't tell offhand if that's a bonded or a floating neutral block in the box... – ThreePhaseEel Jul 2 '19 at 2:37
  • Also, how important is that GFCI receptacle to you, and how practical would it be to replace the run to this box? – ThreePhaseEel Jul 2 '19 at 2:38
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    Gfci not really. I'd like to keep some power on that side of the house but it's not the end of the world. I cant seem to add another pic but it's a GE tfn60rcp. The diagram on the safety cover shows it as EQUIP GRD. Also they decided to put the disconnect inside the house so I have my wiring running from a new disconnect outside back to this one running 12/3 throughout. – Delecron Jul 2 '19 at 3:30
  • I take it that you've put a 20A breaker in at the panel for this circuit? – ThreePhaseEel Jul 2 '19 at 11:37
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    Sounds like I need a dedicated ground or I need to get rid of the outlet. If something is plugged into the outlet its going to send current into the neutral back into the ac. Sound correct? – Delecron Jul 3 '19 at 2:22

You either need to run a ground or get rid of the outlet

Right now, the GFCI hooked to the disconnect in your picture effectively bootlegs ground off of neutral, and the disconnect box itself is grounded via its neutral as well. This means you either need to run a ground wire (10AWG copper will do) from this disconnect back to the main panel or the grounding electrode conductor system (by any path you can manage), or re-run the feed to this disconnect with a new cable (12/3 W/G will do since this is now a 20A circuit through and through, even).

Of course, you can also remove the GFCI and its feed, and then simply nut off the white in your cable to the mini-split as unused, landing the bare wire on the existing ground lug. This technically abuses a white wire as a ground, but given that it's not also performing the function of a neutral at that point and that it runs directly back to the main panel, it's not going to be a major issue, practically speaking. Of course, if you're going through this work, you could just remove this disconnect altogether given that it seems to be in a rather odd/useless place, replacing it with a simple junction box and a new run of 12/3 from the j-box to the main panel.

  • Thanks, I'm going to kill the gfi and run it's own circuit when I have time next century. Thank you again! – Delecron Jul 3 '19 at 2:39
  • @Delecron "next century"? :P – ThreePhaseEel Jul 3 '19 at 2:56
  • I heard people say things like that in the 90's ... :) – Harper - Reinstate Monica Jul 3 '19 at 16:56

I'm really mystified by this box because it looks modern - note blade disconnect and general shininess of components. However the box is built as if the requirements for separate ground/neutral do not exist, and the "groundless" /3 cable is definitely a relic of a past age. The only thing that makes sense is if the box is intended as a disconnect for air conditioners or water heaters, which do not need neutral but do need ground.

Regardless, you cannot run neutral through that splice block, period, because the splice block is tied to the chassis and you cannot "ground" equipment to neutral. It will become live if neutral is disconnected somewhere between here and the panel.

Of course, you could have neutral pass through on an insulated Polaris connector or other floating splice, and then retrofit a ground wire and use that terminal for actual ground.

There is no Code legal way I can see to re-mark that white wire to make it a ground. I thought I had found something at 250.119(B) but that's not applicable here.

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    This entire house is a Goddamned enigma literally – Delecron Jul 3 '19 at 18:38
  • From the soil in the ground to the electrical – Delecron Jul 3 '19 at 18:38
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    It is indeed an "air conditioner" type of disconnect, hence the bonded through-lug for the grounds + the lack of a neutral lug. – ThreePhaseEel Jul 3 '19 at 22:27

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