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I'm planning a hot tub installation (nothing built yet). The current plan is:

  • 50A 240V 2 pole GFCI breaker indoors (added to existing 100A subpanel)
  • 4-wire from subpanel to exterior disconnect (2 hots, neutral, ground)
  • 4-wire from exterior disconnect to hot tub

I prefer the GFCI indoors to keep it out of the weather. That way the exposed disconnect is relatively inexpensive if it ever needs replacement.

I might not actually need a 4-wire (TBD) but it seems silly not to just have it and future-proof.

Most if not all disconnects I can find (either for "spas" or air conditioners) are 2-pole. So the question is: what to do with the neutral wire at the disconnect?

  • Does it need to be switched also, ie is a 3-pole disconnect required?
  • Even if not required, is there any benefit of switching the neutral anyway?
  • If not, how to connect the two neutral wires within the disconnect enclosure? Wire nuts? Bus bar? (Maybe if THWN is used it could just be continuous.)

Location: USA

I should add that I've looked at some PDFs of a few disconnects (when they are even available) and haven't seen this detail addressed. Maybe printed instructions would cover it but I didn't want to purchase anything before having a full plan.

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  • You will need a neutral at the hot tub, count on it. Also do check the label on your 100A panel to verify that it is UL (or other NRTL) approved to install the GFCI breaker there.
    – NoSparksPlease
    Jul 11, 2020 at 14:49
  • @NoSparksPlease its a GE panel that takes THQL... breakers (types are listed on the label). There are already some 1-pole GFCI's in there, do you mean that a 2-pole GFCI could have different requirements?
    – StayOnTarget
    Jul 11, 2020 at 14:50
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    Some inspectors are real detailed about the labeling. If the list on the panel cover or installation instructions of approved breakers doesn't include the GFCI version of the breaker that may mean there isn't enough wire bending radius or other complication that prevented it from being approved. If a single pole was approved it's likely the 2-pole is, but rely on the list.
    – NoSparksPlease
    Jul 11, 2020 at 14:55
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    @NoSparksPlease That should be taken care of, as long as OP is playing by the other rules, that require you use breakers listed or classified for panel (e.g. GE, or Eaton CL). A great many panels predate the existence of GFCI/AFCI, yet, the breakers are legal in the panel.
    – Harper - Reinstate Monica
    Jul 11, 2020 at 15:02
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    @NoSparksPlease -- I've seen quite a few hot tub setups that are 208/240V only (i.e. they're like air conditioners in that their controls are 208/240V in addition to having 208/240V "guts", so they have no use for a neutral)
    – ThreePhaseEel
    Jul 11, 2020 at 15:11

4 Answers 4

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Neutral should not be switched. Ideally the disconnect box supports a neutral bar, but if not a suitable wire nut or any other code compliant wire connection method for in-box connections is suitable. 50A is not a small amount, though, so I'd shy away from wire nuts, as you should be using a 6 awg wire. Putting two of those into a wire nut requires a special wire nut. At this size you should instead consider a split bolt connector.

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Another option would be polaris connectors, which don't require the effort needed to properly insulate a split bolt.

Wire nuts, split bolts, and polaris connectors are less convenient than a neutral bar. You don't have to worry about whether you've tightened and secured the wire nut enough, insulate the split bolt, or take up as much space as all three options. For split bolts, make sure you understand how to insulate it properly - it often requires several layers of two or more different coverings to do properly.

Also please be aware that ground and neutral should be separate at this point. If you place a neutral bar in there you might be tempted to make it look like the main breaker box, and connect both neutral and ground to the bar. This will interfere with the GFCI operation. If you use a a neutral bar make sure it is insulated from the box and ground. Some neutral bars are not insulated, so even if the ground isn't connected directly to the neutral bar, they might be connected due to the way the neutral bar is attached to the metal (grounded) disconnect box.

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    I did end up using a Polaris connector, for #6 wire. I'd used those before and found them much easier and worth the small cost over a split bolt. There was enough room in the disconnect switch for it to fit pretty easily.
    – StayOnTarget
    Sep 22, 2020 at 21:31
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You never switch the neutral, well, "never" is a strong word, sometimes some special generator installations switch the neutral, but almost never should you switch the neutral, just the 2 hots. I like your idea of putting the GFCI inside to protect it.

To connect the neutral, there is usually a small bussbar you can land those on. If your new hot tub doesn't require a neutral, just cap it off in the disconnect.

Your idea about just passing the neutral thru the disconnect unbroken works too.

You got this!

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    If the small bus bar is not present usually the part number for the "neutral kit" is on the cover.
    – NoSparksPlease
    Jul 11, 2020 at 17:29
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Keeping the GFCI indoors will cut the cost of a GFCI disconnect but be prepared to shell out some bucks for indoor GFCI. It's a great idea to still run the neutral, you never know when you might want to change out that cheap disconnect with a little subpanel (think about it). You would just cap the neutral in your disconnect box with a wire nut and leave it disconnected in the main panel. There is no need to switch it and no advantage.

You ask about connecting two neutrals in the disconnect box. I'm assuming you mean grounds since you've already stated you don't need the neutral. The grounds should be connected to a grounding bar in the disconnect which would also ground the box.

If you meant connecting neutrals in the bos in the event you ran them, wire nuts would be the way. Plain disconnect switches usually don't have a neutral lug. If you used a GFCI disconnect then that would probably have a neutral bar that you would attach to.

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  • I did mean how to connect the neutrals - what I meant was that you have one white wire "In" from the house and another "out" to the hot tub, and what the proper method of connecting those would be. (Assuming I do end up requiring a neutral.)
    – StayOnTarget
    Jul 11, 2020 at 14:52
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    @UuDdLrLrSs I added that to my answer.
    – JACK
    Jul 11, 2020 at 15:04
  • @JACK I agree with you on a small sub-panel rather than a simple disconnect. I was practically assuming that in my answer but should have mentioned it. I have a small sub-panel for my hot tub which I also put in a 120v circuit and gfci protected outlet which was in an ideal location for my outdoor lighting transformer.
    – George Anderson
    Jul 11, 2020 at 15:15
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Cap it off at the disconnect

Hot tubs, by and large, are single-voltage, 208/240V loads, connecting to two hots and a ground. As a result, you'll want to simply cap off (insulate) the neutral at the local disconnect using a wirenut of the correct size. There's no sense in bringing it further, nor do you need to provision a pole for switching it, so a bog-standard two-pole air-conditioner pullout disconnect works.

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