DIY Message Boards
220V Spa Heater Wiring

This topic can be found at:

Nov 12, 2013, 04:55 PM
220V Spa Heater Wiring
First post so here goes...

I have a swimming pool and hot tub at home that use a 5.5kW 147000 BTU heat pump to heat both. For the hot tub, the heat pump doesn't work so well below ambient air temps of 57F. Therefore, on cold nights the hot tub struggles to stay above 96F.

To keep the tub toasty I plan to add an 11kW electric spa heater (CSPAXI11). The heater I’m planning on buying has an 220V 3 wire hook up. The install instructions recommend a 2 pole 60A breaker at the main panel routed through 4 wire (6 AWG) to a local pool area spa sub panel (as per code), then through a 60A GFCI breaker to the new spa heater.

I already have a pool sub panel breaker box next to the pool equipment. It's fed by a 60A breaker at the main panel and the wire from the mains to the pool sub panel looks like 4 AWG (looks bigger to me than 6 AWG but I can’t see any writing on the insulator yet). The feed is routed along the side of the house in grey plastic pvc conduit to the pool sub panel.

The problem is that the pool sub panel already has inside it, a 60A breaker to the 5.5kW heat pump, a 50A breaker to a 2.5hp circulation pump, then a few more 20A breakers to the lights and other outlets etc. It does have space for another two pole breaker that could power the new spa heater, but can it handle another 50A load?

So, I’m caught in two minds.
1. Do I get a 60GFCI breaker for the new heater and pop it into the pool sub panel and use the existing wiring feed.
2. Do I follow the heater instructions and install yet another sub panel using 6AWG over a 35 foot span from the main outlet box. The wire is $225 for 100 feet at home depot..

If the mains to pool sub panel wire is 4AWG will the wire support the load of a heat pump, pool pump and spa heater?

Please help.
Nov 12, 2013, 08:10 PM
It already sounds like you are overloaded. With only 60a supplying the sub-panel you already have two large loads pulling fro it (one 50a and one 60a). Hard to imagine how if even those two kicked on at the same time that it wouldn't trip the 60a supply breaker on the main panel. toss in the loads from those other 20a breakers and it gets even worse.

If your main to sub supply line is a #4 then you may be able to go up on breaker size at the main panel, maybe enough to power that new 60a breaker. But local codes vary - you are certainly close to being overloaded already. I would get a local electrician to check this out and either do the work or advise you as to what you can and can't do here.

Nov 13, 2013, 07:55 AM
I too am surprised that when the heat pump and circulating pumps run simultaneously that a breaker would not trip. A clamp on amp meter would provide the answer to that riddle. Chances are you may not have one in the work shop, but you never know.
Adding another circuit with a high amp draw would doom your scenario, methinks. In actuality you would not run all three {heat pump, circulator pump and hot tube water heater at the same time, but you could}. And with the predicted results, tripping the breaker. Remember voltage drop has to be factored in as well. But a 35' run should not be an issue. Always a treat to siffer that in as well. But a must just the same.
By adding a new hot tub heater circuit you will quash all problems that may present itself. That is to install wiring from the from the new breaker in the main panel as the per the instructions.
It may sound odd to install a breaker in the main panel then later install a GFCI breaker on the same circuit. But the first breaker will protect the circuit to the sub panel and the second breaker {a GFCI type} will protect the heating unit itself. Mainly because you can add other circuits in the new sub. As was done in the first sub you now have in place.
You may be able to tackle pulling the new cable through the PVC present. But that entails doing a calculation involving the diameter of the PVC present and the wire size and amount of cable in that run. Then adding in the new pull as well. A certain amount of a copper cable can be tugged in any certain sized PVC piping. The NEC has guidelines and charts that cover that. By adding another properly sized PVC run you are placed ahead of all your problems. And yes I realize another run looks like crap on the side of your house. The other option would be a complete upgrade to house the new & old circuit run, but that would increase the cost dramatically.
Clear as mud? By the description of your problem you seem to have a good working knowledge of electrical work, keep the questions coming. Oh yea, shop around for the copper as that price seems high.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...
Nov 13, 2013, 09:16 PM
Thanks for the replies. After more reading and the help from you guys I figure that I need to install another sub panel just for the spa. Home depot sells 60A GFCI included spa sub panels for less than the price of the GFCI alone!

I'll be using 6 AWG THHN wire through a plastic conduit along the side of the house, adjacent to the existing conduit. I was going to use romex then read that it's against code because the GND must be insulated in outdoor conduit, especially when used for spa applications. THHN it is!

So, if I'm right all I need to do is buy a 60A 2 pole breaker for the main, 40ft of THHN, red, black, white and green, 1" grey plastic conduit by 40ft, the new heater and the spa sub panel with 60 GFCI breaker already included.

I think I have a clear picture in my head now. Thanks again for everything.
Nov 14, 2013, 07:49 AM
Sounds like you have a good handle on your project and material list needs. Good for you.
I would make one or two suggestions. If any part of the run is outside and I'm guessing part of it is. {If not just forget about my suggestion}. You are planning to purchase THHN cable. This type of cable is rated as dry & damp location use by the NEC. I would think about the option of purchasing THHW cable, rated for damp & wet locations. Really no price difference as far as I can tell as my supplier charges the same price for either type. Not sure about a big box store though. I would think they would stock THHN and THHW at the same price, but once again, not sure.
Even though the run will be protected by PVC most anything outside {exemptions are possible} is considered a wet location by the NEC. They realize any type of outside run will sooner or later have moisture present, and correctly so.
Also in some cases inspectors require any PVC that is exposed to be schedule 80, not the more common s40. As in a lawn mower crashing into the run by a careless teenager. Just one more to thing to think, but it may not be a problem for you.
Some PVC straps can be added to your list as well. As I recall metal straps can not be used legally on PVC. But I may have to look that one up. {I always use plastic straps on plastic and metal straps on metal}. On the run you may have 90 degree turns so pull elbows would help with the tug. {Those elbows that have a removable cover plate, allowing easier access}. If not regular 45 or 90 degree elbows will suffice.
PVC cleaner & glue can be added to the list as well, if none lying about the abode workshop.
Romex can be run in PVC if needed, as long as the run is indoors, as Romex is rated for dry residential locations only. Romex can not be run outside in PVC, according to the NEC. Just adding to your post.
Good luck with your project. Wink

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...