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I’m trying to have a hot tub installed that requires a 50amp breaker.

My main panel is a quad-throw 200amp service see photo #1 This main panel feeds 2 other sub panels - one to the garage and one to the basement. I’m wanting to have the hot tub 50amp breaker installed from the garage sub pane - picture #2. I’m worried that since the main panel appears to be feeding 125amps mac to the garage panel and 50amps of that is going to be used by the hot tub that there won’t be enough amps left in that sub panel (125 total) and things will start tripping.

Am I over concerned?

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  • How many square feet of space does the garage subpanel serve, and what dedicated or small-appliance circuits does it feed, if any?
    – ThreePhaseEel
    Oct 4, 2020 at 1:23
  • It serves devices all over the home. The panels are strange. On the garage panel it has breakers for the furnace, 2 bedrooms, frig, dishwasher and some lights...
    – Paul Snyder
    Oct 4, 2020 at 1:46
  • Items in the garage sub panel are: master bedroom (TV and lights); guest bedroom (computer, router, monitor); disposal; frig; dishwasher; disposal; garage door opener and garage outlets; garage GFCI and; radon system removal fan
    – Paul Snyder
    Oct 4, 2020 at 2:04
  • I think it's important to note the the TOTAL ampacity of all the breakers in a panel often totals more than the panel ampacity. This is because all loads aren't used simultaneously, especially the many 20amp 120v household circuits.
    – mark f
    Oct 4, 2020 at 3:25
  • @PaulSnyder -- can you get us the square footage of the bedrooms, and the HP rating of the garage door openers as well for that matter?
    – ThreePhaseEel
    Oct 4, 2020 at 3:42

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I assume the 2nd pic is the sub-panel in your garage? If so, you should be fine installing the breaker for the hot-tub in the garage, since it has a 125 amp feed. That is unless you have lots of other simultaneous heavy loads, which I don't see breakers for. Just because the amperage of the breakers adds up 170 amps in that panel isn't a problem. Panels are over-subscribed all the time.

Using the capacity of every breaker at the same time, is a virtual impossibility.

The heating element size in common hot-tubs is 4 - 5.5 KW which is 16.6 amps and 23 amps respectively. And it will not nearly be on all the time. Additional draws will come when you use it and start running pumps. But the total draw will be less than 50 amps.

Again, just because you have the circuit capacity doesn't mean you are using it. If you were using all the capacity of every circuit in your house (ignoring the fact the main breaker would trip), you'd need a very large loan to pay your electric bill!

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  • Yes. The 2nd pic is the sub panel in the garage. The breakers in that box are: refrigerator, furnance, garage outlets, dishwasher and washer and various bedroom lights. The AC and dryer are a separate breaker in main panel (see pic). So you don’t think the new 50amp hot tub breaker will cause items to trip?
    – Paul Snyder
    Oct 4, 2020 at 1:49
  • 1
    Paul, not meaning to be insensitive, you really don't understand how breakers and panels work. What "items to trip" are you concerned with? Certainly other breakers in the same panel as the 50 amp for the hot tub would be completely unaffected. About the only thing that could trip would be the 125 feed to the sub-panel and that would only if you had the hot tub running at full tilt and most of your other garage circuits maxed out. Again, just because you have a 20 amp circuit doesn't mean it's capacity is being used. A 125 amp feed is very adequate, even with the hot-tub.
    – George Anderson
    Oct 4, 2020 at 3:12
  • Thank you. I appreciate the help.
    – Paul Snyder
    Oct 4, 2020 at 3:38
  • I might be concerned (even without the hot tub) about a possible imbalance. Even though you would never reach the max load of 80A and 110A on the two 125A legs most of the breakers on leg A are 15A, which would typically be general purpose receptacles which don't get heavily loaded, and leg B is heavily loaded with 20A breakers which often feed kitchen, bathroom, and garage receptacles which tend to get more heavily loaded. I would likely try to move one heavily loaded 20A circuit to leg A.
    – NoSparksPlease
    Oct 4, 2020 at 15:55
  • @NoSparksPlease How did you determine which breakers are on which leg? To me the panel looks perfectly balanced. Are you saying the top part of the panel is on one leg and the bottom part is on the other? I've never seen a panel like that.
    – George Anderson
    Oct 4, 2020 at 16:07

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