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Robester 05-02-2006 06:17 PM

Hot tub Sub-panel installation ?'s
Hi.. I've dabbled in electrical circuits before, adding to the main panel doesn't scare me at all for instance. But now I'm finding a need to add a sub-panel for a hot tub, and I'm finding that I have more questions than I thought I would! I'm hoping that folks here can help with these questions that I've come up with so far!

The tub's directions say I need 230v, but I thought a 2 pole breaker from a main panel would mean that I get 220v. Is there something I'm supposed to do to get 230v, or just live with the variance that is within toleration and probably built-in?

I ran #6 aluminum wire, about 70 feet. It has an SER rating. Should I go back and change that out to copper? I only needed #8, but given a long run I went with the higher gauge so that I wouldn't have a significant current drop over the run's length.

The sub-panel needs to go outside... I can't seem to find the 'rules' for mounting it other than at least 5 feet away from the tub. Can the sub panel mount to the side of my house? Does it have to be on plywood on a post standing free of the house? Some specific distance away from the house? What kind of guidelines are there for mounting the sub panel!?

That's the set of questions that I have at the moment.. anyone that has answers or thoughts would get my appreciation and thanks!


MAS2006 05-02-2006 11:22 PM


This site shows typical install. Safety first. Check on permit requirements/inspection for your area. Could become an issue if resale of property at later date.
Power company controls voltage, most have been increasing it over the years. 240 volts is pretty normal today.

Its voltage drop not current drop. You have to have current flowing (heater/motor on) to check for a voltage drop(at load).

Load amperage and distance(there and back your 70ft becomes 140ft for calculations) determine wire gage.
A disconnect is what is required for spas.

Sparky Joe 05-03-2006 06:42 PM

Mas said it all. But I'm wondering how much current(amps) the spa draws and why you went with aluminum, because that brings on another set of issues?

Speedy Petey 05-03-2006 06:58 PM

So many DIYer throw around 220 volt, 240 volt...yet very few mention wattage or amperage.
The voltage is only half the equasion. And no, there is no difference between 220v, 230v and 240v.

The SER is likely fine to feed the disconnect panel, but NOT the spa feed. It is rare that spa instructions do not mention to use only copper to feed the control panel in the spa.

Robester 05-03-2006 07:48 PM

Great info
Hi everyone.. thanks for the tips so far. The aluminum was just hanging around, 6 guage that I had for an electric stove I think, so I used it. The Spa sub-panel says copper or aluminum now that I have that panel, but to use an anti-oxidizer on the aluminum at the connections. And yes, I'll use only copper from the sub-panel to the spa!

The spa when converted to 230v ends up having a 30 amp and a 20 amp circuit to feed the jets and heater. The heater will run at 6000 watts and while the jets run, while before at 110v, only the jets or the heater ran, and the heater at only 1500 watts in that configuration. Hence my desire to go to the heavier voltage. Nothing else in the book seems to indicate the amps required other than the 30 and 20 amp circuits required.

I'm still trying to figure out the mounting of the sub panel if anyone has ideas.. it's fairly small, so I was thinking of a post in the ground. Not sure I really want to put a small piece of plywood on the house and mount it there, since it would have to be on top of the vinyl siding if I did it that way. And if I use outdoor wiring from the sub panel to the spa, do I need to put it in conduit?

Thanks again for the tips so far... I'm still trying to figure this out as you can tell.. it was raining here the last few days so I haven't done more than the inside wire at this point.


Speedy Petey 05-03-2006 08:13 PM

I would mount it on the house, or possibly a deck? I do not like the post idea myself.

You must use conduit outside. You must use insulated conductors (THHN/THWN) and the ground must be insulated as well. You are allowed a maximum of 6' of flexible "sealtite" conduit at the tub.

I must say, a spa is really no place to learn as you go. Installed outdoors they are treated much like a pool with quite a few special codes.
I hope you have all the information you need before you start so you don't make any expensive (cost and otherwise) mistakes.

Sparky Joe 05-03-2006 08:32 PM

sealtite is the best way to go, just be sure to mount your disconnect/subpanel close to where your electrical hook up is on your spa, though I think I heard 5 feet away in another post?
Don't put plywood on your house because that doesn't look good, just mount the box to the house however you wouldv'e mounted the plywood.
You mentioned the specs called for a #8 wire but you went with #6 for voltage drop, was all that related exclusively to aluminum conductors, because remember aluminum isn't as good a conductor as copper so they don't cross refference the same.

Robester 05-03-2006 08:36 PM


Originally Posted by Sparky Joe
You mentioned the specs called for a #8 wire but you went with #6 for voltage drop, was all that related exclusively to aluminum conductors, because remember aluminum isn't as good a conductor as copper so they don't cross refference the same.

I went with the aluminum mostly because I had it around, and also thinking that 6 guage was better than the required 8. I'm not sure where to do the calculation at this point, and I know that running 70' of copper is going to be the highest cost of the project. Albeit if it's the right thing to do, I certainly would want to anyway!

Speedy Petey 05-03-2006 09:05 PM

If the specs called for #8 I'm sure they must have specified copper. #8AL is too small for very much with regard to a spa.

The #6AL is fine for the feeder, just use #8cu for the portion to the tub.

As long as the disconnect is within sight (less than 50'), but no closer than 5', you are fine.

Sparky Joe 05-04-2006 07:16 PM

There is no calculation between cu and al(and I've lost what page my "K"s for copper and aluminum are on) but your #6 al puts you right at 50 amps. I wish I could find my constants to see if your still within your 5% for feeders, anyone else have them on hand?
About the anti-oxidizer, use it on all your aluminum terminations because while aluminum is a good conductor, aluminum oxide is a horrible one. You can find it at home depot in the electrical section, "Ideal" makes some called "Noalox" in a blue and white bottle. Just coat all the exposed aluminum real good with it before you put it under the lugs.

Robester 05-04-2006 07:25 PM

230v hot tub conversion accomplished!
Thanks to everyone's tips, I've finished the conversion. I did end up changing out to copper for the feeder, just felt better than having aluminum based on the comments here even though it probably wasn't necessary. The sub panel box went in fine, mounted on the house and conduit from inside the house to the panel, and from the panel down to the ground and under and across to the hot tub. All went without a hitch, though I had to make a few trips to home depot for parts and the local store didn't have some of what I needed so looked elsewhere.

The final test was turning it all on and lo and behold, no smoke! :D Seems to be working fine! Thanks again everyone!


Sparky Joe 05-05-2006 02:18 AM

you should just take that aluminum down to the scrap yard along with your beer cans, if it were my choice I'd never use aluminum where I sleep.

Speedy Petey 05-05-2006 05:22 AM

C'mon Joe. You know larger aluminum wire (#6 and bigger) is perfectly safe.
There are certain instances it should not be used, but it IS safe.

Sparky Joe 05-05-2006 12:45 PM

Just did a job with 6 parallel runs of 750 aluminum, was a lot happer landing that aluminum than I would've if it were 500 kcm copper

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