EV Charger: #8 Romex on 50a Breaker

Fred B

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
Other than the fact Romex (NM-B) is only allowed to be at the 60oC rating thus #8 only good for 40A.
Every EVSE that I've installed (3 different brands I deal with) all had wire sizing listed with the equipment indicating for the 40-48A to use min. size 90 deg wire of #6AWG, protected by a 50A or 60A breaker. Those 2 factors would mean no NM or UF or any 75 Deg wiring, per mfg. specs.
 
R

retirede

Senior Member
Location
Illinois
Fred B said:
Other than the fact Romex (NM-B) is only allowed to be at the 60oC rating thus #8 only good for 40A.
Every EVSE that I've installed (3 different brands I deal with) all had wire sizing listed with the equipment indicating for the 40-48A to use min. size 90 deg wire of #6AWG, protected by a 50A or 60A breaker. Those 2 factors would mean no NM or UF or any 75 Deg wiring, per mfg. specs.
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Are those hard-wired EVSEs?

It would seem very strange for them to dictate the type of wire used if the unit connects with a cord and plug. As long as the mating receptacle is installed in compliance with the NEC, it should be sufficient.
 
Fred B

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
retirede said:
Are those hard-wired EVSEs?

It would seem very strange for them to dictate the type of wire used if the unit connects with a cord and plug. As long as the mating receptacle is installed in compliance with the NEC, it should be sufficient.
Click to expand...
Hard wired, I won't do receptacle, had issues with GFCI - charger conflicts and nuisance tripping.
 
C

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
There is no issue running a 50 amp circuit with #6 NM-B for a 40 amp charger. A 48 amp charger requiring a 60 amp circuit would require #4 NM-B.

NM-B has 90C conductors but the ampacity is limited to that of 60C conductors.
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Birken Vogt said:
How did it come about that the 60C NM limitation was removed from SE cable about 10 years ago?
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I believe some testing was done in 2009-2010 around attic temperatures and cables a report got published. That got SE cable that is installed in thermal insulation de-rated for the 2011 NEC.
then later more testing of SE cable revealed its XHHW insulation larger than 10 AWG is fine in thermal insulation so the need to de-rate was removed from the 2017 NEC
Birken Vogt said:
My supply house lists 8 Cu SER in the catalog, but it is not in stock - have to order 1000 feet.
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How much is 1000' reel?
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
8/8/8gnd Cu SEU 1.73 no stock, don't know what they would say if tried to order
6/6/10gnd NMB 2.24 in stock by the foot
4/4/4/8gnd NMB 6.91 in stock by the foot - 4/2 not available
6/6/8gnd SEU 2.29 not in this region but others seem to be selling by the foot
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Birken Vogt said:
8/8/8gnd Cu SEU 1.73 no stock, don't know what they would say if tried to order
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That 8/3 SER seems like a good investment, between hi-end ranges that recomend a '50 amp circuit' and EV chargers I bet its worth us stocking a spool, I am going to look into that. The other option would be a some of that tray cable thats now listed for Joist pull.
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
That is 8/2 SER with bare ground. From the illustration it looks like a round stranded ground but it is not always accurate. Might be concentric.

I was just typing out all the conductors found in the cable to be precise there.
 
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