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I am currently wiring for a spa. Have dug an 18 in trench. I will run (4) #6 wires to a 60 amp breaker box approx 55ft away from the main panel and then run from that box the additional wiring 25ft to the hookup spot for the spa 8ft x 12ft (which will be hard wired. Have a few questions: One, is 1 inch schedule 80 conduit enough room to run the 4 lines of #6 wires?

And two, what changes to the spa wiring could I make if I wanted to convert that area with a small guest home (tuff shed 10 x 20) in the future? The shed would be a small tiny home with bed, small electric stove, some electric outlets for TV, fan, small AC in a window.

This spa project is in Tucson, Az and want to i stall a Tidal Fit Spa 8ft x 12ft panel says 50/60amps. I talked directly to the guys at the spa and they stated not to step down the ground to #8 (as I wanted to do that). The spas is suppose to have (4) #6 wires. The inspector may not pass it. I have been waiting during this time over 20 days just to get a case number to then request an inspector. (See attached diagram).

The spa wiring I feel good about. The part I was hoping to learn about is how can I convert this wiring later on should I add a small room with lights, a few outs and maybe a hook ups for a small electric range and mini fridge. What I am hearing is I could/should add another smaller sub panel.

I AM NOT an electrician just trying to learn from the pros.

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  • what's the nameplate ratings for the spa? – JACK Aug 15 at 17:15
  • Do your instructions for the spa call for 4#6 AWG' – JACK Aug 15 at 17:17
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    Note that you need 18" of cover above the top of the pipe, not 18" burial depth to the bottom. – Harper - Reinstate Monica Aug 15 at 17:25
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    @EdBeal I think I've put some in that just had the GFCI..... maybe there was a stud I didn't notice because I didn't need it. – JACK Aug 15 at 22:11
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    @jack, I just did a search because I may have installed close to 50 of these small subs in my area and honestly don’t ever remember seeing a single double pole box, I was surprised to see quite a few. my big box store and electrical distributors in the area must not Cary them or I just looked at the larger ones for the same reason we suggest bigger panels. The slightly higher cost is offset by a 10$ breaker lockout device (some as cheap as 3$) so so a separate disconnect was not needed, I have the same thing on my current and last 2 homes power powering spa’s and mini splits and water fall.+ – Ed Beal Aug 15 at 23:48
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1” conduit has plenty of room for four #6 copper THHN. Although the ground can be #8.

1” conduit also has room for three #4 aluminum XHHW and a #6 aluminum XHHW ground, if you’d like to save some coin. The lugs are aluminum, do why create a dissimilar metal problem?

Your #6 copper or #4 aluminum may be breakered at 70A, hence my reco for that size of ground.

Having a little kitchen is like being a little pregnant, when it comes to number of circuits required! You still need two dedicated circuits for kitchen counter receptacles. The oven needs a dedicated circuit. Disposal. Dishwasher. Built in microwave. Etc. The bathroom needs a dedicated circuit. Laundry room etc. We are going through panel spaces very fast!

As such the spa panel will not cut it and you’ll want gosh, at least a 20 space... but getting too few spaces is a serious blunder easily avoided, so why short yourself... get a 30.

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  • Problem is, the box they put in now will have to be on a post, which means that it can't be reused for the shed no matter what size it is. – ThreePhaseEel Aug 16 at 22:03
  • Is putting the box on the wall, 26 feet away from the "Jacuzzi hook-up" acceptable, or does it have to be (should be) closer to the point of use so it's easier to turn off in an emergency? – FreeMan Aug 17 at 18:06
  • @ThreePhaseEel Wait, they can't extend off the post to another panel at the shed? Or can't attach the shed to the post? – Harper - Reinstate Monica Aug 17 at 18:37
  • @Harper-ReinstateMonica -- they could extend off the post to another panel at the shed, but that'd just make things more complicated – ThreePhaseEel Aug 17 at 22:26
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Yes, 1" Sch80 is adequate for your proposed feeder...

You are correct that 1" schedule 80 PVC will fit 4 6AWG wires down it, as the wires take up just shy of 132mm2 of space, while that 1" schedule 80 conduit has 178mm2 of usable fill area.

but your trench needs to be deeper

However, the Code burial requirements call for a given number of inches (18 for the PVC conduit you are using) of topcover, not a given burial depth. So, you'll need to make your trench a few inches deeper -- about 21-22" or so will do the trick for most conduit sizes.

Going bigger isn't a bad thing, though!

Going with a larger conduit, such as 1.5" or 2", now is far cheaper than having to dig up the yard to add a larger conduit later. So, I would put a 1.5" PVC conduit in alongside this 1" and use the 1.5" for the mains feeder, leaving the 1" stubbed up with plugs at each end as a spare duct for communications cables to the future tiny house, such as a fiber for network connectivity. (Beats having to jury-rig wifi extenders, that's for sure!)

As to the panel...

Your main problem with your current setup is where you're suggesting to put the panel as having a panel in the middle of the run isn't going to do you any good when you go to put the shed in. As a result, I'd move the panel to where you are suggesting the Jacuzzi hookup box is; you can use a NEMA 3R "spa box" on a post at the edge of the pad for now, provided you position it so that the box is 5' from the edge of the water in the Jacuzzi.

When you put the shed in, though, you'll want to replace that panel with something much more sizeable, considering that you'll have to swap out the subpanel anyway as the shed's panel is required to be mounted to the shed, not some post somewhere, even if that post is next to the shed. When you do that, get a generously sized panel: a 24-space or 30-space, 100A or 125A, main breaker panel is not at all out of place for an outbuilding application. There is no issue with the main breaker having a higher amp rating than the feeder, by the way, since the feeder breaker at the house protects the feeder, leaving the subpanel main breaker to serve as an inexpensive shutoff switch.

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  • Is it considered bad form to oversize the panel? I mean, won't it be deceiving for someone later on to see 100A in the panel and assume they have that much to work with? – DonBoitnott Aug 17 at 16:01
  • @DonBoitnott If someone later adds 100a worth of load, the feeder to the sub panel is still protected by the proposed 60a breaker in the main. If that person attempts to use that much power all at once, the main box breaker will pop without any wiring melting or causing flames to appear. If "future person" doesn't trace the supply back to the main panel and determine that there's only 60a to use prior to setting up the little house, he probably shouldn't be doing the work in the first place... – FreeMan Aug 17 at 16:29
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    I've seen it recommended here often enough, @DonBoitnott, that it seems to be a fairly common situation that your average electrician would understand. Don't know about the average home-owner understanding it, though. I suppose, one could put a label inside the panel, above the main breaker indicating "Protected by 60a breaker at upstream panel" (or similar) if one was feeling generous... – FreeMan Aug 17 at 18:04
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    @DonBoitnott Take a person in Wyoming where the freeway speed limit is 80. They sell 85 mph safety-rated tires, as well as 112 mph and 130 mph tires. Should one use 85 mph tires to "send the correct message" and avoid an admission of speeding? Heck no, the material issue is safety. – Harper - Reinstate Monica Aug 17 at 18:45
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    @DonBoitnott first off, there is no such thing as a 24-space panel with 60A rated bussing. Second, the supply breaker would catch any epsilon-minus who did overstuff the panel. Third, downbreakering the main at the sub creates a race condition due to the fact light-duty breakers don't support selective coordination – ThreePhaseEel Aug 17 at 22:41

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