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We are moving our Spa (50 AMP 240v) to our new home. Currently it is wired to a spa panel via PVC conduit to an extra breaker in the meter combo as there was room for a breaker. The new home has a similar meter combo but this Eaton unit has no extra breaker. It is a 200 Amp main. The main panel is in the finished garage in a wall bump out, about 18' from the service entrance. Here are the two options I've come up with, any better options? Home is in North Florida.

  1. 6/3 Romex from the panel in the garage through the attic to a suitable junction box. THHN wire run through PVC conduit down to the Spa panel, also 6 AWG.

  2. Same as above but conduit from main panel, no junction box. All THHN wire.

  3. Run one of the two above options from the main back to the outside wall where the meter is, down the wall to the foundation with the conduit running along the foundation only a few inches under the soil/mulch.

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  • Just MHO but I'd avoid any junctions for the spa. They take a lot of power. Next: check with local codes but in most places, conduit carrying line voltage needs to be buried at least 12" if not 18". Oddly enough, you could mount it to the house (unsightly) without additional protection. I believe the idea is to prevent people from digging, not knowing it's there and hitting it. Anyway, I'd do the whole run in conduit with THHN/THWN Jun 7, 2022 at 15:49
  • You can surface mount schedule 80 conduit. Schedule 40 requires protection 18” by code. For me I would run 3/4 EMT and rain tight fittings at the level you want I have done many jobs along the foundation in a depression that we all know will be covered later, EMT is listed for direct burial and as I have had conversations with inspectors what’s the difference in at ground level +-6” when the raceway is listed for both above and below. I have not had an inspector flag this even in decades past when EMT was not listed for burial because it was exposed at the time of inspection, but now listed.
    – Ed Beal
    Jun 7, 2022 at 16:51

2 Answers 2

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For 50A you need #6 NM or UF cable, due to its poor thermal performance.
For 50A you need #8 of any other type of copper.
For 50A you can use #6 aluminum (since NM or UF are not sold in aluminum). Presuming the hot tub disconnect is rated for aluminum wire (we presume so).

Note that "Romex" NM cable is not allowed outdoors, so under your deck is not going to work for that whether it's inside conduit or not.

Aluminum wiring is reliable when landed on terminals rated for aluminum, and when torqued to spec (a requirement for ALL large connectors, see NEC 110.14). If you have apprehensions about "small" aluminum wires, then go up to #2 aluminum - still far cheaper than #6 copper. And 90A, if you ever have an interest in running an additional 40A of stuff out of that box.

(A "hot tub disconnect" is simply a 2-space subpanel with a GFCI breaker in it, so you can swap it out for a larger subpanel of the same make so you can reuse the costly GFCI breaker).

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Based on your comment (that answer needs to be removed) in the attic you can use schedule 40 and by code it has to be assembled and glued prior to pulling the wires. Be aware where exposed below 8’ it will need to be schedule 80. So you will have several feet at the box below where you exit the attic,

In many cases I will use an LB type conduit body so it is mounted flat to the house and this provides a pull point then 4-5 ‘ of schedule 80 at this end to the box or panel and the other 1/2 of the stick of schedule 80 into the service panel where I pick up the power.

Everything in the attic can be schedule 40.

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