I need to run a 220 line about 100ft from my breaker box to where the sauna be located.

The manual says for an 8 kw heater, 8-2 w/ground copper; 40 amp non GFCI breaker But it also says for distances “up” to 30 ft.....

So what if it’s 100?

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  • 1
    Longer distances require larger wire to reduce voltage drop due to resistance. Have you looked at standard wiring charts for the correct size?
    – isherwood
    Commented Jan 31, 2018 at 18:43
  • What size are the pumps?
    – Ed Beal
    Commented Jan 31, 2018 at 21:25

1 Answer 1


Having run a few of these calculations, the break point is usually a little past 100' if you want to hold voltage drop below 3%. However, for a resisitive heater, there is no reason to hold voltage drop below 3%. It is a waste of money.

Regardless, 8000 watts happens at 33.33 amps on US 240V* voltage. The UL-approved product instructions call for 8 AWG wire. Southwire's voltage drop calculator tells me those conditions at 100' run yield 1.92% voltage drop on 8 AWG.

If the hot tub failed on 2% power drop, there is no way UL, CSA or TUV would list it.

You're all set.

* power was 110/220 when AC power was first mass marketed in 1915-ish, and the term stuck. Today, US voltage is 120/240. Except in Puerto Rico, where it's 0!

  • Agree but use a GFCI breaker .
    – Ed Beal
    Commented Jan 31, 2018 at 21:49
  • @EdBeal definitely. But the instructions prohibit that, so use a GFCI deadface lol! Unrelated, I've always wondered why hot tubs use resistive heaters and not heat-pump. They'd be so much more efficient, and better yet, electricity would be nowhere near the water (it'd be a freon-water interchange). Though they'd become a motor load. Commented Jan 31, 2018 at 22:38

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