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Question about Gen3 Charger Installation Wiring, advice needed!

Mengy

Active Member
Feb 18, 2020
1,226
9,698
PA
So I had my new Gen3 Tesla Charger installed today and everything seemed to go well. My electrician ran 40' of EMT conduit from my breaker panel out the wall to my carport where the charger is mounted next to where the MY parks. He installed a SquareD HOM 60A two pole breaker in the box. He then pulled two #6 THHN wires and one #10 wire, all copper through the conduit. The #6 wires are on L1 and L2 while the #10 is the ground.

Everything powered up and the MY charges happily at 48A / 11V. However, after ten minutes or so of charging the conduit just past the breaker box started buzzing. Or rather the wires in the conduit were buzzing I'd guess? The electrician says that's normal and won't hurt anything. The breaker isn't getting hot, just a bit warmer than ambient, and everything does seem to work fine.

I'm worried about that #10 ground wire though. He said the ground doesn't need to be #6 and that #10 is fine. Is he correct? Is that causing the buzzing? I'm not an electrician so any advice would be welcome.

Thanks.
 

Mengy

Active Member
Feb 18, 2020
1,226
9,698
PA
I initially had a bad brand new breaker that was buzzing. Can you tell where the buzzing is from?

More or less. The breaker isn't making any noise at all, it's definitely coming from either the wire or the conduit itself about three or four feet above the breaker panel. right about where there is a 90° bend in the conduit.

If the #10 ground wire is fine then I'm not too worried. From what I read online last night it's common for single strands in conduit to hum from time to time due to EM frequency vibration. I'm gonna play around with turning the amperage down in the app today to see if I can vary the hum or even make it stop entirely. Purely for the sake of science of course. :cool:
 

Sophias_dad

Active Member
Supporting Member
Jul 29, 2018
2,173
2,460
Massachusetts
I initially had a bad brand new breaker that was buzzing. Can you tell where the buzzing is from?

Thhn in conduit could have been #8 with #10 ground for 60a. #6 is better for that distance. I’m not sure if the use of #6 then requires a #8 ground??
This is incorrect. #8 THHN in conduit is only allowed to carry 55 amps even if you use the 90C rating. Its only 50 amps if you use the 75C rating like you are supposed to since the endpoints are only rated to 75C. It is unclear why the manual tells you to use 90C rated conductors.

#10 ground is correct for #6 or #8 conductors.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,835
9,856
Boise, ID
He installed a SquareD HOM 60A two pole breaker in the box. He then pulled two #6 THHN wires and one #10 wire, all copper through the conduit. The #6 wires are on L1 and L2 while the #10 is the ground.
Yes, that's all proper for a 60A circuit.
Thhn in conduit could have been #8 with #10 ground for 60a. #6 is better for that distance. I’m not sure if the use of #6 then requires a #8 ground??
No--definitely not! This is a 60A circuit. #8 THHN in conduit is only rated for 50A. (must use the 75 degrees C rating) That's not OK at all for 60A.
 
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