I'm installing a hot tub and have added a 40 amp breaker to my main electrical panel as specified in the manual. The service disconnect came with a 50 amp GFCI breaker.

Is it okay to use the included 50 amp GFCI breaker since everything is behind the 40 amp breaker in the main panel?

  • What does the hot tub require? You need to match the minimum of what the hot tub requires for amps, most anything else is decoration(not really, but the smallest breaker rules them all).
    – crip659
    Commented Apr 24, 2023 at 20:56
  • A GFCI breaker will be more concerned about volt/amp leakage to ground/water and will trip before it gets nasty to people. A dead short is it's second use. Your breaker in your panel is only concerned about dead shorts, you do not matter to it.
    – crip659
    Commented Apr 24, 2023 at 21:17
  • @crip659 The hot tub requires a 40 amp breaker. I've edited the question to make this clear. My thoughts are that the GFCI breaker can handle the GFCI protection and the breaker in the main panel can protect the wiring. Commented Apr 24, 2023 at 21:25
  • 1
    You are right, the 40 amp breaker will handle the power requirements, the 50 amp GFCI will do safety. If either trips, make sure you fix the problem first.
    – crip659
    Commented Apr 24, 2023 at 21:30

2 Answers 2


That should be fine. Here are the basic issues:

  • Feed breaker (e.g., branch breaker in the main panel that has wires going out to your subpanel or other stuff) has to be the correct size or smaller than the wire. In other words, the breaker protects the wire so the breaker better not be larger than the wire can handle. For 40A, that generally means wire or cable that is 8 AWG or larger. (Smaller numbers in AWG being larger wire, so 6 AWG is fine, 10 AWG is not.)
  • Disconnect or "main" breaker can be any size equal to or larger than the feed breaker. So for a 40A feed breaker, the disconnect can be any size 40A or larger. A typical example is a 60A disconnect (a standard size because it is larger enough for nearly any residential HVAC or other system except for a big subpanel), which will often be installed to provide a disconnect/shutoff for outside equipment, even if that outside equipment is connected to a 20A or 30A circuit.
  • Subpanel with a "main" breaker. A "main" panel can be used as a subpanel, with the "main" breaker serving as a disconnect. In some cases (separate building such as a shed) that disconnect is required. In other cases it is not. But whether it is required or not, it can be any size as the feed breaker or larger. In your case, 50A (which is larger than 40A) is just fine.
  • GFCI. Hot tub panels need GFCI protection. That can be at the subpanel or at the feed breaker. So your 50A GFCI breaker in the subpanel is fine.
  • Feed size must match load. This is the one critical piece here that might be an issue. By using a 40A feed breaker, you have effectively limited the subpanel to 40A total, 32A continuous. If your hot tub heater, pump, etc. actually use more than 40A (or more than 32A continuous) then you have a problem. Technically the way to figure this out is a load calculation. But you probably have between 2 and 4 circuits here, so it should be easy enough to just add up the loads to figure it out. You can basically ignore any convenience receptacle circuit and lighting uses almost nothing, so it pretty much comes down to the fixed loads of the hot tub. If that doesn't fit in 40A total/32A continuous then you need a larger feed breaker and larger wire to match.

Your situation with one breaker in the main panel and another breaker in the disconnect near the spa is a common one. You're right: it can be confusing to figure out what's required and what's acceptable or allowed. Hopefully the following guidelines will help.

  • Both of the breakers must have a rating equal to or greater than the "minimum circuit" called for in the spa manual.
  • One of the breakers must have a rating that is equal to or less than the "maximum circuit" called for in the spa manual. The other breakers may also be chosen to be equal to or less than the "maximum circuit," or they may have ratings higher than this.
  • One of the breakers must offer GFCI protection. I believe that technically both breakers could be GFCI, but this is more costly, can create confusion, and does not improve safety.
  • The ampacity of the wire between the main-panel breaker and the spa-panel must match (or exceed) the rating of the main-panel breaker.

So: if you're in the situation of installing all new parts (main-panel breaker, wire, and spa-panel), I'd suggest the following. A 40 amp spa is relatively low-power; spas requiring as much as 60 amps are becoming more common. This suggests than a 60-amp spa might be in your future, so choose the difficult or expensive parts accordingly.

  • Use a 60 amp GFCI spa disconnect panel outside.
  • Use wire from the spa disconnect to the main panel suitable for 60 amps. The minimum wire gauge will vary depending on whether you use NM-B, copper THHN in conduit, aluminum THHN in conduit, aluminum SE cable, etc.
  • In the main panel, use whatever equal-or-less-than-60-amp breaker the spa requires. In your case this would be 40 amps.
  • Confirm that the main-panel breaker, 40 amps in your case, accepts the selected gauge of wire. If it does not then you'll have to use smaller wire and lose the future upgradability to 60 amps, or you'll have to adapt the large wire down to a breaker-accepted size with a block connector like Polaris or Mac/ILSCO.

The advantage of this approach is that if you desire a different spa in the future and it requires 50 or 60 amps, the only component you have to change is the breaker in the main panel (which also happens to be the least expensive part in the whole setup!).

  • Good idea with upsizing the wires. Thanks for the tip! Commented Apr 25, 2023 at 3:04

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