Sauna Wiring Dilema

Old 07-27-23, 10:36 PM
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Question Sauna Wiring Dilema

Hey Fellas-
I bought and put together a barrel sauna from Costco. Now I need to wire it up. There is an existing junction box under my deck wired for 220 (see pic)

Existing wiring under deck
where a hot tub used to be. It is located about 50 feet from my breaker box and it is tied into it with a 50 amp breaker. I need to run the new wiring another 100 to my sauna (50' through conduit connected to my foundation and another 50' underground.).
I'm not sure what wire to purchase. The existing wire is a 3 wire (not sure it's a 10/3 but would be my guess). The Harvia Heater manual says I need a 30 AMP fuse and utilize 10/2, or 8/2 wire if further than 90' from power source, which it is.

Harvia Heater Pic Taken from Manual. This is how I'm supposed to wire it.

My Dilemma:
-Do I just continue with 10/3 and expect voltage drop (takes longer to heat up)?
-Continue with 8/2 wire. (Not sure if I should be mixing them up or if it would even help lessen voltage drop).
In either case would I simply ignore the neutral, when wiring the Heater (see pic)?
Any help is greatly appreciated!
Old 07-28-23, 04:56 AM
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If you have a 50 amp circuit breaker I think you need #6 conductors the whole way. You cannot reduce the conductor size along the run. The circuit is limited by the smallest conductor used. If you replace the breaker with a 30amp then you could keep the existing #8 and add on as small as #10 for the last bit. Me, I'd probably just stick with #8 the whole way to keep it simpler and more flexible for future use.
Old 07-28-23, 09:31 PM
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Hello Dane. Thanks for the response! Okay, good to know. I was planning on switching out the breaker to a 30 amp. Guess I'll just pick up some 8/2 wire run it and hope for the best. Do you happen to know if I would simply eliminate (not use) the neutral from the existing 3 wire?
Old 07-29-23, 06:42 AM
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Is the sauna 120/240 or straight 240?

Your existing install was not compliant. The #10 was only good for 30 amps, not 50.
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Old 08-02-23, 11:52 AM
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Hello PCBoss-

The sauna is a straight 240. I agree. I was planning on changing the breaker to a 30 amp. I'm in a pickle because it seems that the existing wire is #10 and it's hidden in the finished wall, so I can't pull it out and replace with #8. Looks like my only option is to continue with the #10 and deal with whatever voltage drop occurs.
Old 08-02-23, 12:34 PM
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As mentioned... you need to replace the 50A breaker with a 30A breaker.

I would recommend continuing the run in #8 wiring to further reduce drop.
I.... personally.... would continue the run in #8 THWN/THHN wiring in conduit.
You'll have 50' at #10 and the balance in #8.

You will have a problem at the heater. Doubtful #8 will fit in that terminal block.
You may need to add an additional white and black wire.
Connect both blacks to the #8 black and the same for the white.
One tail for ground is ok.
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