Wire Size for outdoor Hot Tub/Spa

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tedbenjamin

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I am installing a new Spa that is rated at 40 amps and 220 v. The Spa is located outside about 80' from the inside power panel. Engineering calculations indicate that there is less than 3% voltage drop using AWG #10. However is AWG #10 too small for 40 amps?
 
Re: Wire Size for outdoor Hot Tub/Spa

I don't know the source of your "engineering calculations," but I used the free voltage drop calculator available from Mike Holt's home page. My result was a 4% voltage drop with a #10, and a 2% voltage drop with a #8.

But to answer your specific question: "No, a #10 cannot be used for a 40 amp load. You need a minimum of #8." Reference NEC Table 310.16.
 
Re: Wire Size for outdoor Hot Tub/Spa

You may want to check the information that comes with the spa.

I checked one today, full load amps 24, max circuit amps 40, and the minimum required wire size was # 6 copper.

I don’t know how they come up with their requirements but since it is on the nameplate, that is what they will get.
 
Re: Wire Size for outdoor Hot Tub/Spa

I don?t know how they come up with their requirements but since it is on the nameplate, that is what they will get.
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Alex That is easy:
They own stock in a copper mine.LOL :D

Kidding aside I think they want to make sure that start up current doesn't starve the pump motor and the fact that breakers are slow to blow when there is any voltage drop.
 
Re: Wire Size for outdoor Hot Tub/Spa

The Spa manufacturer does specify that AWG #6 is required into their electrical box. I am installing an outside Power Panel (with breaker and GFCI) nearby within 5' of the Spa. I was going to use #6 from the Spa to this outside panel. However, I was then hoping to connect this outside panel using AWG #8 to the inside power panel located about 80' away. Does this make sense? Thanks
 
Re: Wire Size for outdoor Hot Tub/Spa

I am installing an outside Power Panel (with breaker and GFCI) nearby within 5' of the Spa.
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Did you mean not less than 5' away from the Spa? Within would be very very bad!
680.41
:roll:
 
Re: Wire Size for outdoor Hot Tub/Spa

Ted
It would not make any sence to wire the spa with #6 and then use #8 80' to feed the panel from the service. as if there is any voltage drop it would be in the longer run to the panel. If the manufacture requires #6 it means #6 all the way untill the next larger size wire circuit is reached this would mean all the way to the main panel.

And Delfa is right this spa panel cannot be any closer than 5' But the code artical is 680.22(C) I believe

680.41 Does not apply to single-family dwellings.

Unless this is a cemercial install?
 
Re: Wire Size for outdoor Hot Tub/Spa

The calculations indicate ~ 2% voltage drop using #8 over 80' for 220 v which seems to me to be acceptable. Is there a reason to go with #6 over the 80' distance. By the way, I will locate the outside panel about 5-10' away from the Spa. I am then uncertain why I would need to use #6 for the 5-10' connection from the outside panel to the Spa. But the Spa directions state that #6 wire must be used into the Spa?
 
Re: Wire Size for outdoor Hot Tub/Spa

Ted, like Alex, you must use the #6 or risk warranty issues.

As far as working, the unit wouldn't care about wire size if the voltage is kept to a 2% drop

Roger
 
Re: Wire Size for outdoor Hot Tub/Spa

What exactly does this tub call for? 40 amp supply or it draws 40 amps?
If it pulls 40 and runs 3 hour (very likely up north)then we apply 125% and that puts us on #6
Most of the tubs i have seen either are the 120 volt 20 amp or large 240 volt that call for 50 amp supply. :confused:
 
Re: Wire Size for outdoor Hot Tub/Spa

appears to be a manufacturer issue.....look at the manual that comes with the spa...there should be a web site, phone number for customer service...ask them why they recommend #6...failure to use #6 could void your warranty! good luck!
 
Re: Wire Size for outdoor Hot Tub/Spa

Thanks for all your help. The Spa Specs simply states the following:

Vac: 240 V. 60 Hz 30A
Service: 40 amp

So I guess that this means that it draws 30 A but requires a 40 A circuit. I believe that I will use #6 from Spa to outsude panel (~ 8') and then #8 from the outside panel to the inside panel (~ 80')

Thanks
 
Re: Wire Size for outdoor Hot Tub/Spa

I think that you are actually looking at 40 * 1.25 there, 50 amp conductors. I think it should say 40 min, circuit if it meant 40 amp. what country does this spa come from??
 
Re: Wire Size for outdoor Hot Tub/Spa

For the slight differance in cost i think i would use #6.Chances are high that it draws 40.They did say #6 and that would be correct if it draws 40 allowing for 3 hours.How much will it cost if you use #8 and burn out the tub? They will walk away saying VOID.Unless i could get a better spec i would go with #6 and 50 amp.I have wired several tubs and often see #6 50 amp being the spec.
 
Re: Wire Size for outdoor Hot Tub/Spa

Hi Ted,

Just a little insite from a commercial contractor; Most info plates are pretty informative and specific. I have yet to see a name plate that asks me to calculate or assume the full load current based on information presented.

From my experience, the plate provides the "facts sir, just the facts". Unless MCA (min ckt amps) and MOCP (max over current protection) are stated, it would be questionable to assume the given load is anything other than 'full load amps'. My experience is that the use of the item then determines the duty cycle for load adjustment to the circuit.

If this came across my desk and based on concurring discussions, I would spec #6 back to the main panel.

Cheers, and good luck. Jeff
 
jimwalker said:
Would the 125% rule not apply here ?? :confused:
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I would use at least # sixes and a 2-pole 50 beside the code requirement for location. The electric heating unit feeders shall be 125% of the rated load.
Under NEC separate overload device Art. 430.
 
Just a note if manufacture state a minimum wire size that is in excesss of the calculate circuit ampacity and you choose to use small conductor, they could void warranty.
 
tedbenjamin said:
The calculations indicate ~ 2% voltage drop using #8 over 80' for 220 v which seems to me to be acceptable. Is there a reason to go with #6 over the 80' distance. By the way, I will locate the outside panel about 5-10' away from the Spa. I am then uncertain why I would need to use #6 for the 5-10' connection from the outside panel to the Spa. But the Spa directions state that #6 wire must be used into the Spa?
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The reason is because the nameplate says use #6, it would never pass inspection using #8, and all installations regardless if permitted or not should be capable of passing inspection.
 
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