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I have a strict 240V wiring situation (i.e., two hots + ground, no neutral) with a hot tub as the only load on the circuit. Now, I think it’s very prudent (and generally mandated) to have a local disconnect with a GFCI breaker...which gets tricky with no neutral.

The scenario is pretty well illustrated by this image (i.e., "Configuration 2" from this previous post)

enter image description here

The other post concluded that using the neutral is the way to go - and I would have posed this question over there, however:

  • the topic appears to be closed for comment, and
  • there's a key distinction here - there is NO feasible, code-compliant way (and trust me I’d like to) to run a neutral line from the main panel to the disconnect via any available/feasible conduit paths...there's just not

So it got me to thinking, what exactly is wrong with “Confugration 2”??

And before there are a ton of knee-jerk "it's not code" or "you can't do it that way" responses (as in similar posts), please bear with and hear me out to help consider the best, safety-minded solution for this unique situation (i.e., the 'spirit' of the code vs. pedantry about the strict letter of the code)

  • For starters, I realize that the EGC (i.e., green 'ground wire') is never intended as a substitute or equivalent for the neutral wire and that the two should never be tied together anywhere but the main panel - not disputing that, not proposing that
  • I also get that since a GFCI breaker ‘monitors’ the current traveling through the valid conductors to infer a 'ground fault', all those conductors must be connected to/pass through the GFCI
  • And lastly, while many 240V appliances do in fact also have 120V circuitry (e.g., the clock on a stove) where the neutral is a key component and a valid conductor, in my case there is NO NEUTRAL anywhere and therefore the neutral never could/would/will be one of the valid conductors

And some validation tests show that:

  • No surprise, the GFCI won't work if the pigtail is not connected (to something) so my contention is that the GFCI must have the neutral (or something) as a proxy/reference to ground to properly function
  • And lo and behold, the normal, expected functionality is there when the pigtail is connected (gasp!) directly to the ground as depicted in the image

So the outstanding questions are:

  • Is the GFCI breaker purely passive/electromechanical and only 'activates' and trips (e.g., electromagnetically) when enough current flows throught an unintended path?
  • OR is there also an active/electronic component in there that's continuously consuming (probably minuscule amounts of) power and sending (probably minuscule amounts of) current along the ground line in this setup?
  • Even if the latter, it's reasonable to think that the amount of current going along the ground line must be so small as to be below the threshold of the GFCI line and therefore relatively "safe", correct? (until it isn't, like when you hit the 'TEST' button or a legit ground fault)

Sooooo...given all that, would you agree or disagree that - in a situation where there is/can be no neutral - it's at least better to have a GFCI there connected like this than to have no GFCI at all?

(and bearing in mind that I agree nobody should opt to do it this way if they can avoid it)

Thanks and curious to hear the discussion...

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  • It's closed for comments from new contributors. You'll need 15 reputation and you only have 11 but I'll make it 21 right now. Make sure you take the tour and know when to comment. Apr 2, 2022 at 4:40

4 Answers 4

13

Put the GFCI breaker at the supply panel. Done & dusted!

Now, I think it’s very prudent (and generally mandated) to have a local disconnect with a GFCI breaker...

Not quite right. There is no safety benefit whatsoever to having the GFCI be local, right at the hot tub. In fact, it presents several problems.

  • If it's near the tub, it might get wet. Current could possibly use the water to bypass the GFCI and zap you anyway.
  • For that and other reasons, the GFCI must be a minimum distance away from the hot tub.
  • Pool/tub chemicals (chlorine etc.) are very damaging to wire and electrical components, as such, most cable types are banned near pool equipment and hot tubs.
  • That, plus generally being outdoors, makes it a sub-optimal place for a GFCI. Would you store an iPhone there?

The better place to put it is back at the main panel which supplies the hot tub subpanel.

So congratulations - you dodged a bullet! You can simply put a 2-pole GFCI breaker legal for your panel at the other end of the /2+ground feeder cable to the hot tub.

Note that 1"/2" wide breakers are not interchangeable between brands, even though they seem to fit. Don't waste $90 on the wrong brand of GFCI.

You say in a comment you're dealing with a Bolt-On panel. Seriously? Then buy a $18 2-space panel such as a BR24L70SP (or -RP outdoors), mount it inline along the conduit near the panel, and stick the appropriate GFCI breaker there.

You may need a neutral wire, though.

And here's a hitch that may oblige you: NEC 680.42 which invokes NEC 680.22(A)(1). This requires a 120V receptacle between 6 and 20 feet from the tub.

If there is already a socket in the area, or if you can extend a 120V circuit here, definitely do that instead and forget this section.

But if your only option is to pull it from this panel, then you may need to re-run the feeder so you can install a 15A/20A circuit for the receptacle.

Now if you follow my "GFCI back at the main panel" plan, you don't need any more GFCIs. You can use plain breakers in a plain 4-space panel (or even 2-space with a quadplex) to serve the 240V hot tub and a plain WR 120V receptacle. And they just inherit the GFCI protection provided back at the main.

there is NO feasible, code-compliant way (and trust me I’d like to) to run a neutral line from the main panel to the disconnect via any available/feasible conduit paths...there's just not...

That sounds like defeatist language. In comments you say it is 3/4" EMT conduit and you have #4 in there for 60A. Let's have a look at 310.15(B)(16).

enter image description here

Since we're not using NM or UF, stay out of the 60C column.

There is no 60A wire, but #6 Cu is 65A (when it's not UF or NM). #4 Al is also 65A, but 3 of those won't fit in 3/4" conduit.

Three #6 Cu will fit inside 3/4" conduit with room for a bare #10 ground (if you even need that; it is EMT after all).

What's wrong with bootlegging?

So it got me to thinking, what exactly is wrong with “Confugration 2”?

The problem with your question is confirmation bias. It is to your disadvantage to find the reasons. But...

When you misuse ground for neutral, it's not ground anymore - it's neutral. And now you have the same problem as 3-wire dryers and ranges. When the neutral wire breaks on those, it guarantees the chassis of equipment (in your case all grounded things locally) are energized.

Now maybe your local ground rods do their job. But then you're creating a *voltage gradient" across the earth. Metal things like fence lines can let people get shocked anyway, and the GFCI can't help here (unless it's back at the main panel).

You think the small GFCI load limits the damage? Nope. Joe Innocent comes along, aiming to add that Code-required 120V receptacle. Assumes your installation was correct and "does as the Romans do", attaching their neutral next to yours. Now you're in it!

Look, you probably need proper neutral for the 120V circuit anyway. But even if you don't, just follow ThreePhaseEel's solution -- that's tried and tested; afew years ago we had someone from the Philippines using USA equipment exactly this way. Don't even splice the neutrals to the neutral bar, you don't want someone tempted to hang a 15A socket on it. Just nut straight from transformer to GFCI pigtail.

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  • "You could replace the entire cable back to the panel. You just don't want to :)" Does that include replacing the concrete on top of it? If the conduit's routed under concrete I'm going to agree with him that adding the neutral wire is unfeasible.
    – Joshua
    Apr 3, 2022 at 21:10
  • @Joshua the last guy was able to get power out there, and there's always a way. It just boils down to $ or DIY will/skill. Apr 4, 2022 at 2:35
  • @Joshua Whoever dug the trench, knowing that there would be concrete on top of it, should have elected to install a properly-sized conduit which would allow a neutral to be later pulled through it. Apr 4, 2022 at 4:39
  • @JonathonReinhart: No doubt. But what's the recourse when the city inspector did not do his job properly in the original inspection for work done by a prior owner.
    – Joshua
    Apr 4, 2022 at 17:00
  • Thanks for all the input and a few responses to the above:
    – DIYnot
    Apr 4, 2022 at 22:25
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Yes, GFCIs are electronic devices that consume (a tiny amount of) power.

Here are a couple GFCI ICs:

https://www.ti.com/lit/ds/symlink/afe3010.pdf

https://www.onsemi.com/pdf/datasheet/ncs37010-d.pdf

In theory somebody could make a GFCI breaker for pure 240V applications that's powered by the two hots only, but demand for such a thing is probably very low. Manufacturers simplify their production by using one power design for both single- and double-pole breakers, and getting 120V by using hot/neutral in the two-pole models.

If the instructions that are supplied with your GFCI says it must be connected to neutral (no ground) you must follow that.

Your GFCI doesn't have to be at the local disconnect. It can be at the upstream panel, and the local disconnect can be a "dumb" switch.

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  • 1
    Shouldn't you be able to order one from Europe?
    – Joshua
    Apr 3, 2022 at 4:07
  • 1
    @Joshua -- European-style devices made for the US market aren't available in Class A (6mA) sensitivity, only equipment protection (30mA), and are not certified to the UL 943 personnel protection GFCI standard, only the UL1053 standard for generic equipment/fire protective GF relaying gear. Apr 3, 2022 at 14:19
  • @nobody -- Thanks for the schematics...helpful to know and tricky to find! In my own test since the first post, the GFCI circuitry was pulling about 20mA, which hopefully is validation enough to go with the undersized neutral approach.
    – DIYnot
    Apr 4, 2022 at 23:44
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Since all you need to do is power the GFCI itself, a small transformer can fix this

As already mentioned, GFCI breakers require a neutral connection to power their internal electronics. However, since they do not require much power themselves, and your load has no use for a neutral, it's possible to use a transformer to generate a neutral return for the GFCI breaker to use from the two 240V hots.

The simplest way to do this is to use a 120/240V, 50VA buck-boost transformer (often sold as a lighting transformer) and connect the outer primary terminals (H1 and H4) to the two incoming 240V hots via an appropriate breaker, then tie H2 and H3 together to use as the "neutral" return for the GFCI breaker. I'd recommend nutting the neutral pigtail on the GFCI directly to the wire from H2/H3 instead of landing it on the neutral bar in the box to denote that something odd's going on here and hopefully stop someone from overloading the transformer by connecting other loads to it, by the way.

As to the secondary wires, they get capped off individually as we aren't using them for anything in this application. Code-wise, this probably isn't in the scope of 210.9 as we're trying to power the final OCPD on the circuit, instead of something that's downstream of it, although the NEC doesn't really discuss cases where single-phase OCPDs need funny business in order to operate (NEC 450.5(B) is the closest to our situation, but that Code language only applies to three-phase systems).

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  • Certainly this would work, but is it practical? That is, are NRTL-listed devices available, and do inspectors accept it?
    – nobody
    Apr 3, 2022 at 16:53
  • @nobody -- the transformer itself is NRTL-listed (it's a standard dry-type dual-winding buck-boost/lighting transformer), the issue is entirely at inspection time as the NEC doesn't really envision a single phase circuit protection device needing external help just to get an operating power supply Apr 3, 2022 at 21:39
  • @ThreePhaseEel -- this seems like a clever solution even though I'm still wrapping my head around it. Given your moniker and proclivities, I'll come clean and confess that the the main here is actually a 3-Phase Y 208V (didn't want to over complicate the first post) and I already have a buck-boost transformer in place to get the 1-Phase 240V. Any wizardry to mimic a neutral from the available leads there?
    – DIYnot
    Apr 4, 2022 at 23:59
  • @DIYnot are you served with all 3 phases, or do you just get a "2 out of 3" split-phase-ish service with 2 phase hots and a neutral from the 3 phase supply? Apr 5, 2022 at 2:57
  • @ThreePhaseEel -- all 3 phases exist at the main panel, yes. Out where the transformer and disconnect are (which is really the only feasible mounting place for each/both) we are just down to the 2 split-phase-ish situation (although don't even really need it "split" apart from the GFCI). Thanks and let me know if anything else to clarify...
    – DIYnot
    Apr 5, 2022 at 18:46
-2

I’m not an electrician but I do sell and work on hot tubs. Here is the problem that I foresee: if you don’t have a true neutral then your hot tub won’t be able to split the power to 110 to power things like a circulation pump.

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  • 1
    Welcome to Home Improvement. please take the tour to see how things work a bit differently around here. OP claims that he has zero need for a neutral with his particular set up. Of course, this is questionable, considering the need for a 120v "convenience outlet" near the tub. TBH, though, this would be better as a comment, since it doesn't actually answer the question.
    – FreeMan
    Aug 12, 2023 at 12:12
  • @FreeMan Agree. Except that the infinite wisdom of StackExchange, a new user can't comment! Aug 13, 2023 at 2:05

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