Breaker/Junction Box

Question

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.

Answer 1

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.

Answer 2

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.