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Use 8 gauge instead of 10 on 8 foot run from panel to garage ceiling heater? Heater is GHP model EG10000DH, 10000w, 240 volt, 41.66 amp and 7500W, 36.1 amp. Have plenty of 8 gauge...

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  • what is your question?
    – RMDman
    Oct 23, 2022 at 23:08
  • You'll have plenty of #8 AWG left after this because you can't use any of it.
    – JACK
    Oct 23, 2022 at 23:52

2 Answers 2

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8 gauge is for 40 amps at best. You will need 6 gauge on a 50 amp breaker.

Don't even think of 10 gauge.

You need to go by the max amps of the heater, plus a derate of 80% so the wire does not heat up and burn the house down.

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  • Maybe. Depending on the insulation, #8 may be rated for 50A @ 75 degrees C. Oct 24, 2022 at 0:35
  • @JulieinAustin - maybe - as long as the terminations in the heater and on the breaker are 75C rated too.
    – brhans
    Oct 24, 2022 at 0:41
  • Yup, but since the poster has the #8 already, and 75C breakers are common enough, all that matters next is the heater terminations, which I'd wager are 75C because it's a heater. I do agree, as a practical matter, that the OP should just use #6 and call it good. Oct 24, 2022 at 0:45
  • Very interesting. The manual calls for 10 guage, but my 8 guage is really not good enough...I'll check the wire rating. Regardless, sounds like 6 guage with 50 anp braker. Thx.
    – Tommy
    Oct 24, 2022 at 11:39
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    @Tommy Manufacturers can use smaller gauge for plug wires. If they used a 10 gauge wire and plug is okay, but you would need to use 6 gauge to wire the receptacle. The 10 gauge on the heater would have been tested, but your wiring is not tested and needs to go by code. 10 gauge is suppose to be used only with 30 amp breakers, which your heater would probably trip all the time from over load.
    – crip659
    Oct 24, 2022 at 12:12
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10000w, 240 volt, 41.66 amp and 7500W, 36.1 amp

The figures marked in italics are not high/low. That is the figure when used in a 208V circuit, which I doubt you have.

It's a 10,000 watt heater. Amps are 41.66A.

You will need to derate that by 125% giving 52.0 amps, and the wire and circuit must be rated for 52 amps. 50A wire will not cut it.

6 AWG copper or 4 AWG aluminum are both good for 55A. That is your minimum wire size here. A 50A circuit breaker might work but you are supposed to take 52A and then go to the next available size, which will be 60A. If the instructions say otherwise, follow the instructions. You must install according to instructions, NEC 110.3.

Have plenty of 8 guage...

Then trade it on Craigslist etc. for the cable which you do need.

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