I am trying to install a dryer at the far end of a large house. There is already a 220 circuit on a designated circuit running back there to operate a hot tub. The breaker box is full so no room to add another. Is there any way I can tap into that circuit at the far end of the house and run both the dryer and the hot tub? Can I swap out the 10 gauge wire that's there now with 8 gauge and/or increase the size of the breaker? Thanks, Steve

  • So you have access enough that you can replace the entire run of wire? Then using larger wire and installing a sub panel should be an option, right? Is there a reason that isn't possible? – JPhi1618 Oct 22 at 17:06
  • what is your main panel rated for? Can you include a picture? – JACK Oct 22 at 17:08
  • What size (amperage) breaker controls that 220 run to your hot tub? That's the most important question. You can't exceed the breaker max current (duh); if the hot tub max draw is at that limit, then at best you'd have to turn off the tub every time you use the dryer. One would hope that the existing wiring is rated to match the breaker, not the end items on the line. – Carl Witthoft Oct 22 at 17:32
  • Can you post photos of your main panel please? Are you moving the existing dryer to a new location, or installing a 2nd dryer? – ThreePhaseEel Oct 22 at 23:36

First, a ground wire and neutral is mandatory for this setup. You cannot set up groundless, and you cannot "bootleg ground" off neutral as once was legal for dryers. This is extra important because if a neutral wire has a problem, it will electrify the grounds - and that'll shock and drown people in the hot tub.

If the hot tub already requires a 30A breaker, you should convert it to cord-and-plug connection. Use NEMA 14-30 and extend the circuit to serve both 14-30 receptacles. Why? No receptacles are allowed if any hardwired load is more than 50% of circuit capacity (as the hot tub certainly will be). BUT multiple receptacles are allowed on a 30A circuit. Of course, running both at once will trip the breaker, but you know that.

If the hot tub uses a larger breaker, you must install a subpanel. However you will not need to upsize the wire run, unless you want to.

If you go the subpanel route, don't be tempted to install one that's "just large enough". That's how your panel got full in the first place, which is why you have this problem now. The cost differential for a larger panel is tiny a couple of pizzas. You often hear me say "I hope the guy who bought that panel really enjoyed that latté" because it's that cheap, so it's a waste not to do it. Install a large subpanel (in terms of number of spaces) - a 30-space is not excessive. Then as convenient, move some existing circuits to it to free up space in your main. A house should have a number of spaces in the 40's, so if you have a 16, a 30; if you have a 24, another 24.

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