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I had a spa panel installed when the home was built for a future spa. Now we've found a spa and it requires 60a breaker at the panel. The panel has a 50a breaker in it. The panel inside the house at the other end has a 60a breaker. The wire between the panels is 6 AWG copper. I've read 4 gauge wire would be better for the 60a but also that the 6 gauge wire is enough and is what is required per the spa manual. Can I just swap the 50a breaker for a 60 at the spa panel and not have to install 4 gauge wire and a 60a spa panel?

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  • Is your main panel Square-D QO (skinnier breakers with windows on them and only 1 handle even if the breaker is multi-pole) or HOMeline (wider breakers, no windows, a handle for each pole with a crossbar, or "tie" attaching them if it's a multipole breaker)? Aug 13, 2019 at 22:55
  • Yes, they all have the little windows, one handle for multi pole
    – Andy
    Aug 14, 2019 at 0:48
  • Does your spa require both 120 and 240V, or just 240V? (Most only need the latter...) Aug 14, 2019 at 1:55

3 Answers 3

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Your #6 wire is good to 60A. (Actually it's good to 55A, but they don't make 55A breakers, so you get to round up to the next available size).

As such, there is nothing wrong with fitting a 60A supply breaker inside your main panel.

The ruling question is whether your spa subpanel's internal buses are able to handle 60A. Did they put a 50A breaker there to protect a spa they never bought? Or is it there to protect the subpanel itself? Model numbers would help us research this.

Separately, if it is not attached to the house, it will need a main disconnect switch or shutoff. Usually the cheapest way to get a shutoff is to use a sub-panel with a main breaker (just using the breaker as a switch, not a breaker).


So what's up with people telling you that you need to bump to #4 copper? (which you would never do by the way, you'd use #2 aluminum if you needed that, which you don't). They are probably up-in-arms about that because of the long distance, and voltage drop which results.

However, voltage drop is the victim of an "old wives' tale", cheerfully amplified by the sales departments at wire manufacturers. The wrong info is to calculate voltage drop on breaker trip current, and that 3% is condemning. Wrong and wrong.

Actually, calculate voltage drop on what the load actually is (if you are at breaker trip current, you have bigger problems). And 3% is a rosy ideal; depending on application, 6%, 8% (Code starts objecting at 8%) or much more are perfectly acceptable. And this is one of those applications where you have a lot of slack.

So you don't even need to think about voltage drop for this spa below 250 feet of run. (That's not universal. On some circuits it's a concern in as little as 100'). Even above 250', I'm only saying find a piece of paper to run some numbers.

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  • The outside panel is a Homeline 50amp spa panel
    – Andy
    Aug 13, 2019 at 19:31
  • @ Harper do they still manufacture TW & UF? I don't see it anywhere.
    – JACK
    Aug 13, 2019 at 20:03
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    @JACK Competent shops surely have UF. You can't go outdoors with NM-B. Aug 13, 2019 at 20:11
  • @Andy is your main panel also HOMeline? Aug 13, 2019 at 20:21
  • The main panel is square d
    – Andy
    Aug 13, 2019 at 20:27
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If it's a 50 AMP panel then you'll need to upgrade it to a 60 amp panel with a 60 AMP breaker. The #6cu is good for 60 AMPS so that will work. The #4cu would be a waste of money. You will need GFIC protection at one set of breakers.

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  • Is there any de-rating needed for a spa? That's a constant load, right?
    – Jeffrey
    Aug 13, 2019 at 19:03
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    Its a 50a panel. Ive had two electricians give me different answers. First one says as long as its 6 gauge wire, maybe just replace the panel outside with a 60a panel. That I'm ok with. Second guy says he wants to run all new 4 gauge and a new 60a panel. I'm thinking just to upgrade the panel to a 60a and call the 6 gauge wire good.
    – Andy
    Aug 13, 2019 at 19:04
  • 55A, unless you have unusual conditions that allow using the 75C column. But you get to round up to 60A. Aug 13, 2019 at 19:16
  • Is there something specific to the panel that would limit it to 50A? Wire lugs or something?
    – JPhi1618
    Aug 13, 2019 at 19:18
  • @JPhi1618 more like the fact that there is no such thing as a HOM260GFI... Aug 13, 2019 at 22:55
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You'll need to swap the spa box out to do this

Unfortunately, the loadcenter used for the HOME250SPA has 50A busses per this Square-D FAQ, which means it can't handle 60A (and even if it could, there's no such thing as a HOM260GFI to use with it for your application). So, even though your wiring is good for 60A, you'll need to replace your spa box in one of two ways, as NEC 680.13 requires a local disconnect here:

  1. Get a 60A spa panel (or assemble one) and a QO260 for your main panel (to replace the feeder breaker there). If the feed to the spa box is 4-wire, this is what I would do, as this provides maximum flexibility later in the form of being able to put a subpanel in instead of an ordinary "spa box", or use spare slots on the spa box if it has them, even.

  2. Replace the spa box with a 60A, non-fused, AC disconnect box and then use a QO260GFI in the main panel to provide GFCI protection to the hot tub. This is best if your existing spa panel feeder is 3-wire, as the QO260GFI can't handle a mixed 120/240V load due to the fact it lacks a load neutral connection.

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