0

Got a new spa I want to replace old 40amp sub with a 50 amp sub GFCI ( the only one available ) it is on a dedicated 40 amp from the main. Maybe a stupid question but can my main be less than my sub?


A little more info.

Spa only requires 30amp because it is much smaller than the previous spa, and I never had trouble with the breaker. I just wanted to add in the GFI for safety reasons, because it wasn't required 10-15 years ago when original was installed. it was city inspected when I originally put it in, so wire size, type, conduit are all to "code"

2 Answers 2

2

If the current panel is fed from a 40 ampere breaker, with wire rated for 40 amperes. Installing a 50 ampere breaker in the second panel is pointless, since the 40 ampere breaker will trip before the load can draw 50 amperes.

If you want to upgrade to a 50 ampere breaker in the second panel, you'll have to upgrade the breaker in the main panel, and the conductors feeding the second panel. Then you can install a 50 ampere GFCI breaker in the second panel.


After new info.

If you're putting in a 50 ampere breaker; even simply for GFCI protection, all the wiring downstream of the breaker must be rated for 50 amperes.

A circuit breaker is designed to protect the wiring and devices connected to it. If you have a 30 ampere load (the spa) protected by a 40 or 50 ampere breaker, than the load and wiring could carry 40 or 50 amperes before the circuit breaker even thinks about reacting. So unless the wiring is sized to dissipate that amount of heating, then you're creating a dangerous situation.

My advice is to put a new 30 ampere GFCI breaker in the second panel. If that's all that the spa requires, why muck about with anything else. If the store doesn't have what you need, order it, or go to a different store.

The best way to know for sure, is to contact the local Electrical inspector. It's going to be their call as to whether or not they pass your wiring.

3
  • My understanding of the OP's question is that his new SPA is also rated for 40 Amps. He's replacing the sub with a GFCI which he can only get rated for 50 Amps. As you say, the SPA and wiring will still be protected at 40 Amps by the breaker in the main panel. The sub is only there to provide a disconnect and GFCI protection. Isn't this OK?
    – DoxyLover
    Jun 25, 2015 at 19:22
  • 1
    A little more info. Spa only requires 30amp is much smaller than previous spa and never had trouble with the breaker. I just wanted to add in the GFI for safety reasons because it wasnt required 10-15 years ago when original was installed. it was city inspected when I originally put it in so wire size, type, conduit are all to "code"
    – Markyo
    Jun 25, 2015 at 20:41
  • 1
    @Markyo You should have included that information in your original post. It's difficult to answer a question when you don't have any of the facts.
    – Tester101
    Jun 25, 2015 at 22:22
-1

Absolutely. Everything downstream of the breaker in the main panel is protected to 40 Amps, as required. The sub breaker is really only providing CGFI protection.

Removing my answer, deferring to @tester101's experience. (Not actually deleting the answer to keep all of the comments.)

4
  • You are awesome thanks. I know just enough to be scary :)
    – Markyo
    Jun 25, 2015 at 19:02
  • The breaker in the secondary panel is protecting all the wiring downstream from it, so that wiring must be able to handle the appropriate amount of current. In this case, the wiring must be capable of carrying 50 amperes.
    – Tester101
    Jun 25, 2015 at 22:44
  • If you have a 40 amp breaker upstream of a 50 amp breaker, isn't everything downstream of the 40 amp breaker, including the wiring downstream of the 50, protected by the 40?
    – DoxyLover
    Jun 25, 2015 at 23:46
  • @DoxyLover I guess it would be up to the inspector. It might fall back to doing things in a workmanlike manner, as this is an atypical installation method.
    – Tester101
    Jun 26, 2015 at 1:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.