Hot Tub Wiring Size

[overlandsea]

Can someone help double check my reading of proper wire size please? Almost everyone seems to suggest #6 wire for 240v hot tubs no matter what.

My tub I just got has this electrical information from the owner's manual:

240v/50 amp configuration
Voltage: 240 volts
Current Draw: 40 amps
Number of Wires: Three
Circuit Breaker: 50 amp dual pole

It just says use what the NEC says for wire size.

My reading of NEC seems to indicate that wire and breakers should be 125% of max load (125% of 40 amps = 50 amps). This makes sense why the manual would indicate a 50 amp breaker. My question is that if #8 THHN is rated for 50 amps, is that not the appropriate choice? 65 foot run if that's helpful.

I'm happy to use #6 if that's what it needs-just trying to fully understand. Thanks in advance for the help!

[Tman122]

There is a certain drop in load carrying ability in all wire and 65' is a good size run. Calculating the load carrying drop is difficult. While it may be slight over kill to run #6 it could be slight under kill to use #8 may be better in the long run to go with heavier wire..

[Isaac-1]

Another reason to go with #6 is if you ever get a 60 amp tub in the future.

[overlandsea]

Yes, I can see the planning ahead idea being a good one. I believe voltage drop would only be about 1.5%, so that shouldn't be an issue.

Any other thoughts on the matter out there?

[Quickbeam]

I would go with #6. I don't know what brand of tub you have or whether it is new or used. That being said there are a lot of tubs on the market now that take 60 amps, which requires #6 wire. In my case, we had a new home built and had it pre wired so we could put a hot tub on a roof deck. I didn't know much about hot tubs and didn't pay much attention to the wiring. Turns out the electrician only wired for 50 amp service. I bought a Jacuzzi tub, which will run on 50 amps, but if I have both jet pumps running, the heater will kick out. I ended up paying extra money and had the electrician run new wiring so I am now wired for 60 amps. I wished I would have wired for 60 amps in the first place as it would have saved me quite a bit of money. I say plan for the future. Pay the little bit extra it will cost you and go with the heavier gauge.

[aeajr]

For 50 amp circuit I would go with #6, no doubt about it.   I believe that is what is required for 50 amp circuit anyway.

https://answers.yahoo.com/question/index?qid=20100603082208AAtc78H

According to NFPA 70 of the National Electrical Code, #8 TW copper is good for 40 amps, and #6 TW copper is good for 50 amps. You could get away with using #8, and probably not have any issues in the near future. The problem is that TW wire, which is what you would be using in a house, is rated for 75*c,; over time the wire will be heated and cooled many times, and so the insulation will become brittle and crack and fall off. #8 will become hotter than #6 under the same load. So 20 years from now you might have a fire because you chose #8 today.


Never undersize your wire.   The risk is high and the cost compared to the risk is low.   When in doubt go to a larger size, lower number.