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I trying to run a 50A circuit to an outbuilding (sauna) from an existing outbuilding (detached garage). I know there are multiple approaches, but my current plan is to add a 50A GFCI breaker to the garage panel to feed the sauna.

The panel in the garage is a GE TM20DC. I spent an hour looking for a GE 50A, double-pole, GFCI breaker with no luck. HD lists one, but it is out of stock. The best I could come up with was a used one (THQL2150GFT) on Amazon for $200.

I can't understand why this is so hard to find; I would think that there are a million GE panels out there and anyone putting in a hot tub needs one of these breakers. I'm very new to this so maybe I'm missing something obvious. I started looking for a compatible breaker from a different company, but that's not a short putt either.

Any help would be appreciated.

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  • The number of people who do need 50 amp GFCIs is low. Most circuits that big can be hard wired if local regulations require plug ins(stoves, heaters, welders, EVs) to have protection. They make a few and it is first come and the others wait.
    – crip659
    Dec 27, 2023 at 15:27
  • Related: diy.stackexchange.com/q/238800/55930
    – Machavity
    Dec 27, 2023 at 16:07
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    Do you need a single 50 amp breaker to run a single circuit or need a 50 amp breaker for a feeder, running a few smaller circuits?
    – crip659
    Dec 27, 2023 at 16:46

3 Answers 3

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240V GFCI is a relatively new thing. 240V GFCI for large circuits is an even newer thing. This commonly comes up with EV charging, and there the solution is to hardwire the EVSE (the "charger") to avoid the GFCI breaker requirement because EVSE includes built-in GFCI.

In your situation, the solution is to not use a GFCI breaker as the feed breaker. Instead, install GFCI breakers for each branch circuit in the sauna panel. A typical setup is that most circuits in that subpanel will be much smaller (15A, 20A, occasionally larger) and therefore GFCI breakers will be much more readily available.

While it is not likely an issue for a typical sauna subpanel, keep in mind that due to the low US GFCI threshold current (6 ma), cumulative leakage current from multiple circuits can trip a large GFCI. That is different from many other places where a whole-house RCD is used with a threshold typically around 30 ma. If you put an entire house on a US 6 ma GFCI it would likely result in too many nuisance trips. 50A subpanel with 3 or 4 circuits would probably be OK - if you could find the 50A GFCI breaker.

A few quick notes that apply to any new outbuilding subpanel:

  • Ground rods required (normally 2, if it is a new building and you can put an ufer ground then that's better)
  • 4-wire connection - hot/hot/neutral/ground
  • Local disconnect required. That can be a separate disconnect (like an air conditioner disconnect) but you can also use a "main breaker" in a subpanel (true main breaker or backfed, locked down, main breaker used as a main breaker).
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  • I believe there's a path to putting a spa and lights in an outbuilding without a subpanel. You're allowed one circuit each voltage to a detached building, so you can run the spa circuit with the required local disconnect, then a 120V circuit with GFI protection for the 680.43 required outlet and the 210.70 required light. No ground rods or subpanel needed unless you want to do more out there that won't fit on the 20A lighting circuit. Of course saunas are outside my area enough that I'm not 100% sure you could get away with the same in that case, but it really looks like it from here.
    – KMJ
    Dec 27, 2023 at 21:00
  • I believe technically you could do that. But it would mean running extra wires and frankly just doesn't make sense to me. Dec 27, 2023 at 21:15
  • Thanks, I took your suggestion and used a non-GFCI breaker as the feed breaker in the garage and will install GFCI breakers in the subpanel in the sauna for the receptacle circuits. -The two rods were not on my radar I'll look into that. -Yes, got the four wires today. 8 ga for the red, black, white and 10 ga for the green. -I'm going the route of the backfed main breaker in the subpanel in the sauna building.
    – tfinan
    Dec 28, 2023 at 0:21
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"Online" is a bad way to buy electrical gear. 98% of electrical sales and 99.9% of specialty item sales are to licensed electricians. They shop at electrical supply houses, who are cheaper (big box store being cheapest is a lie; that's only true on a few loss-leader items.) Electrical gear is heavy for its cost, so it's very easy to have orders where shipping > item cost. That's a bad look, so sellers fold the shipping cost into the item price (which bites them when the customer returns the item). All this adds up to: anybody who tries to sell electrical gear mail-order gets nothing but novices for customers, and they are high-support and high-returns. So nobody makes an effort to rep electrical gear online; we see whole product categories with zero mail order sellers.

So your best bet is to grab the old Yellow Pages (of course, they're online now) and look under "Electrical supply houses". Call them and find one that is a GE dealer. They will know how to get it.

I started looking for a compatible breaker from a different company, but that's not a short putt either.

The only line compatible with GE panels is Eaton CL, and they don't make 2-pole GFCI breakers. CL is a specialist line made specifically for competitor panels. The common 1" wide breaker types (HOM, BR, QP and THQL) are not interchangeable with each other and the vast majority of bus stab burn-ups we see are alien breakers.

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    Thanks for your insight into how the business works. I can see how that would create online "component deserts." I'm avoiding the issue by changing course and using a normal 50A to feed the sauna and will use a GFCI on the couple 15A circuits that feed receptacles.
    – tfinan
    Dec 28, 2023 at 0:29
  • Probably for the best, but I've never heard of a spa heater that didn't need GFCI. Dec 31, 2023 at 2:42
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One way around this could be the use of a 'spa panel'. Use a normal 50A breaker in your detached garage where it's difficult to locate a GFCI breaker. Then use a spa panel right next to the sauna fed from that breaker. This panel will be a disconnect with a 50A or 60A GFCI breaker in it, effectively a special case of a very small subpanel. Unfortunately, because 50A GFCI breakers are not a cheap item, this will not be a much cheaper solution. It will let you use a breaker series that has commonly available GFCIs though, and give you the benefit of having a disconnect adjacent to the sauna, something which might be required based on local code anyway.

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    Perhaps counter-intuitively, high-amp 2-pole GFCI breakers are sometimes both cheaper and more readily available when purchased as a "spa panel" rather than a loose breaker! Also it's perfectly OK to use even a 60A GFCI spa panel at the sauna and a plain breaker of 50A or whatever the sauna requires to supply the feeder in the GE panel. Siemens currently has a 60A spa panel with an attractive price for example.
    – Greg Hill
    Dec 27, 2023 at 17:06
  • Thanks for the reminder about 60A, added it to my answer.
    – KMJ
    Dec 27, 2023 at 17:20

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