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Discussion Starter #1
I installed a electric car charger on a 60 amp breaker that draws 48 amps max. The rating on the NM-B is 60c which is 55 amps but I'm not drawing 60 that's just the breaker to support the 48 amps I need.

Is this okay or should I step down what I'm drawing (40 amps), increase the gauge of the wire (4awg) or change to thhn in conduit?
 

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Naildriver
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6 gauge is fine for the charger on a 60 amp breaker. How would you "step down" your amperage?
 

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Naildriver
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Yeah, ours is rated at 55 amps, but there's nothing in between, so it jumps from 55 amps at 6 gauge to 70 amps at 4 gauge.
 

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Naildriver
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No real need to, as you won't exceed the capacity of the breaker nor the wiring at 48 amps. How long a run from your panel to the receptacle is it?
 

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Very Stable Genius
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Customer told me just the other day that their Chevy Bolt allows them
to set the charging amps it'll draw. They reduce the charge amps when
charging at one of their parents houses to 24A since the charger is on
a D30.

BTW, they're very happy with their new 30A 240V level 2 charger at home.
 

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I believe the car charger would be considered a continuous load under the NEC, requiring the conductors to be sized for 125% of the rated draw of the charger. If the charger is listed for 48 amps, under NEC you would need a 60 amp conductor. Number 6awg NM-B is only suitable for 55 amps as you stated, and is permitted on a 60 amp breaker only when the load is 55 amps or less in a non-continuous situation. JMO
 

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Discussion Starter #9
I believe the car charger would be considered a continuous load under the NEC, requiring the conductors to be sized for 125% of the rated draw of the charger. If the charger is listed for 48 amps, under NEC you would need a 60 amp conductor. Number 6awg NM-B is only suitable for 55 amps as you stated, and is permitted on a 60 amp breaker only when the load is 55 amps or less in a non-continuous situation. JMO
Yeah, this is what I'm hearing. This stuff is so confusing...

Maybe I'll just set the current to 40amps to be safe until I can either run 4# wire or change over to conduit.
 

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Disrespectful to dirt
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Yeah, this is what I'm hearing. This stuff is so confusing...
More so than you think. Here's the code cite:

625.41 Overcurrent Protection. Overcurrent protection for feeders and branch circuits supplying equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the equipment.

I'll save my rant for after the question has been concluded but I will say this is a poorly written and conceived entry. For now, simply size the circuit for 125% of whichever setting you choose to use.

Maybe I'll just set the current to 40amps to be safe until I can either run 4# wire or change over to conduit.
I would personally go with 4-4-6 or 4-4-4 aluminum SEU over NM unless your charger requires copper conductors only. NM isn't a good choice in larger sizes and is a waste of money. The concentric braid on SEU makes it a little more difficult to work with, but the cost savings (about 1/5 the cost of NM in this application) make the trouble worthwhile.
 

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Very Stable Genius
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CEC allows 51A or greater conductor on a 60A breaker. Does the NEC? Beats me. -)
Code ref T13.

Is quoting myself odd? -)
While the above is correct, it doesn't matter in this case. Rule 8-104(6)(a)
requires that the continuous load be no more 80% of the rating of the conductor* or the OCD.
*Which can also be affected by term temps

EDIT: As an aside, this doesn't come up often in Canada as conductors not
rated 90deg are rare.
 
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