I will be installing a Caldera Cantabria hot tub soon and need to run the electrical from my main panel to the GFCI sub panel. I will be installing a non-GFCI 70A circuit breaker in my 200A main service panel. I will need to run the two hot wires, neutral and ground wires approximately 55-60 feet from my main service panel in the front of my basement to the side and then the back of my basement and then finally outside. I am planning on mounting the Subpanel/Disconnect box on the back of the house approximately 1-3 feet after the wires exit the basement to the outdoors. The hot tub will be at least 5 feet away from this, but probably about 6-8 feet away. It will still be within the line of sight.

I have attached a picture of the wiring diagram provided by the manufacturer. Can I use #6 wires from my main panel to my sub panel like the wiring diagram says that I can? Or does it need to be #4 wire? Also what type of wire should be used for this application? The majority of the run with be indoors in the unfinished basement ceiling area, but I will need to run the wire in conduit outside for approximately 1-3 feet.

The sub panel has 2 20A GFCI breakers and then one 30A GFCI breaker. Wiring the 2nd 20A breaker is optional, but required if you wish to use the 3rd dedicated pump for the lounge seat at the same time as the heater. I live in New England so I figured in the winter time the heater will most likely need to run at the same time as we are using the hot tub. I figured it is worth it to wire the 70A option with the 3rd breaker over the 50A wiring with 2 breakers and do it right the first time. I am planning on using copper wiring and not aluminum.

Thank you!

Wiring Diagram from Manufacturer

  • Are you running a NM or UF cable to the spa disconnect from your main panel, or running a conduit with individual wires inside it? (Or are you running some other sort of cable, such as SE, AC, or MC, for that matter?) Apr 27, 2020 at 23:21
  • I read on another post that UF cable is not allowed for hot tub/spa wiring. I would use NM as the majority of the run is in the basement but I will need to go outside a foot or two to connect to the spa subpanel/disconnect box. I was also told that the ground must be insulated so cables would not work. I was thinking about running 4 #4 copper THHN wires from the main panel to the subpanel outside. Do these four wires need to be inside of some sort of conduit for the run in the unfinished basement part? I assume so to keep them all together. What conduit do you recommend for this?
    – jshep105
    Apr 27, 2020 at 23:29
  • The chemicals used in hot tubs make the area corrosive, including areas cheicals are stored. In those areas the NEC specifies RMC, IMC, RPVC, or RTR except for the flexible connection which is allowed to be Liquid Tight Flexible, and also requires an insulated ground. So you would have covert to one of those methods before entering an area where those chemicals are used or stored. Apr 27, 2020 at 23:49
  • "a foot or two" then NM=nope. Apr 27, 2020 at 23:49
  • 1
    UF can be used as a feeder to a spa panel where the disconnect is outside. From the spa panel. Normally I run a liquid tight flex wip with thhn to the spa because it is easy to route the flex to the tubs power j box or control . Depending on your run I would consider pvc conduit and thhn (just about all thhn is thhn/ thwn or thwn-2 so it is ok for outside and inside and cheaper than the nm then going to a junction box for the few feet to the panel, just doo it all in thhn and conduit.
    – Ed Beal
    Apr 28, 2020 at 15:29

1 Answer 1


You'll need conduit for the whole run, but that means you can use 6AWG wires

You will need to run conduit for this entire run; loose wires by themselves just won't do as a wiring method (see NEC 300.3(A) for the reference on this). However, this means you can use 6AWG THHNs (/THWN, since the stuff you get these days is all dual-rated anyway) for the hots and neutral as wires in conduit can use 75°C ampacities when terminating onto suitably rated lugs (as present on all modern distribution equipment), 6AWG copper wire can handle 65A when terminated on 75°C lugs, and NEC 240.4(B) permits you to "round up" to the next higher breaker size under most circumstances we encounter here.

As to what size conduit to run? I would use 3/4" ENT through the basement run through bored holes in the joists, and then use a LB and a short length (<24") of 3/4" Schedule 80 PVC at the outdoor run to make the turn into the disconnect box. The wires exiting the disconnect, then, are run in 3/4" LFMC, using appropriate fittings at each end.

  • 1
    Awesome! Thank you so much. So I will buy 4 #6 THHN wires and run them through 3/4" ENT conduit. As for the disconnect box to the spa pack controller run, can I use the 3/4" LFMC for 1 #8 ground wire, 3 #10 wires, and 4 #12 wires all together coming from the 3 GFCI circuits? Or should I upgrade to a larger conduit size for these 8 wires?
    – jshep105
    Apr 29, 2020 at 22:54
  • @jshep105 -- the fill for the LFMC and ENT works out just fine -- the Schedule 80 is a bit smallish, but that's why you keep the run of that stuff under 2', so you can use nipple fill rules. Apr 29, 2020 at 23:20
  • Can I use bare copper wire for the ground from the main panel to the subpanel/disconnect box? And then bare copper wire for the ground from the subpanel/disconnect box to the spa pack in the hot tub? Or does it have to be insulated wire for the grounds?
    – jshep105
    May 2, 2020 at 22:52
  • @jshep105 -- I suspect that insulated require is required for your specific spa due to listing/labeling issues May 2, 2020 at 22:57
  • 1
    I was told that an insulated ground is required for hot tubs but I wasn't sure if that just meant for the outdoor run from the subpanel/disconnect box to the spa pack inside of the hot tub. Or if it meant the entire run including from the main panel to the subpanel and then from there to the hot tub. I am ordering the wire now and just wanted to make sure. I don't mind running insulated green wire for the ground for the entire run as long as that is within code. Does stranded vs solid copper wire for the ground make any difference?
    – jshep105
    May 3, 2020 at 0:12

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