#8 THHN for NEMA 14-50 EV charging receptacle

[Sierrasparky]

Hi all,
Been a while since I have posted.
I have a small disagreement with a fellow contractor. The question at hand is
Is it compliant to use #8 THHN on a 50 amp breaker given the de-rating due to continuous load as we must follow her in CA?
Oh and the length of the run is under 90 feet so voltage drop should be fine.
Thanks

 

[LarryFine]

Yes, not knowing the load.

 

[infinity]

I know nothing of the California code but what you've described is NEC compliant as long as it's not NM cable.

 

[Sierrasparky]

Ahh Larry I forgot that. 40 amps is the most that I hear the chargers will use with a NEMA 14-50

Yes, not knowing the load.

 

[infinity]

Why would the load matter? He's asking about a 14-50 receptacle. 50 amp OCPD, 50 amp conductor, 50 amp receptacle.

 

[Sierrasparky]

Why would the load matter? He's asking about a 14-50 receptacle. 50 amp OCPD, 50 amp conductor, 50 amp receptacle.

Because of the continuous load de-rating. I say if the load is 40 then ok. If the load is greater then I say no when using #8 THHN at 70 deg C

 

[LarryFine]

Why would the load matter? He's asking about a 14-50 receptacle. 50 amp OCPD, 50 amp conductor, 50 amp receptacle.

I only mentioned it because he said "de-rating due to continuous load" and I didn't want him to think that I was including the unknown load in my answer.

 

[infinity]

Because of the continuous load de-rating. I say if the load is 40 then ok. If the load is greater then I say no when using #8 THHN at 70 deg C

The receptacle, the OCPD, and the conductors (75° C) are all 50 amps. If the equipment is a continuous load and it is over 40 amps would you agree that it cannot have a 50 amp plug on it?

 

[Sierrasparky]

The receptacle, the OCPD, and the conductors (75° C) are all 50 amps. If the equipment is a continuous load and it is over 40 amps would you agree that it cannot have a 50 amp plug on it?

I guess the argument there would be that a receptacle device load cannot exceed its rating when you include the de-rating long and continuous. Some of my colleagues would say oh 43 amps that's ok it's 50 amp rated.

 

[curt swartz]

There is no special California de-rating. Not sure what you are referring to.

An EV charger supplied with a 50 amp plug will have a maximum 40 amp charge current. Most chargers with 50 amp plugs will actually have a maximum 32 amp charge rate.

 

[Sierrasparky]

There is no special California de-rating. Not sure what you are referring to.

An EV charger supplied with a 50 amp plug will have a maximum 40 amp charge current. Most chargers with 50 amp plugs will actually have a maximum 32 amp charge rate.

In CA the load is calculated for EV at 125%, No if ands or buts. Most maybe only 32, however you assume at wall mounted charger plugged into a NEMA 14-50 outlet. That alone is very stupid as we waste wire. The only reason I install still a 14-50 is a obscure 2012 CA law that pertains to Condo HOA common area that require a wall mounted charger to have a 1 million dollar liability policy for eternity specifically written to include the charger. However there is a carve out that allows a receptacle to be exempt. So don't mount a charger to the wall and plug it in.
Many manufactures which plug into a 14-50 are rated at 40 amps charge current.

 

[curt swartz]

Many manufactures which plug into a 14-50 are rated at 40 amps charge current.

California just follows the NEC. Nothing special here.

I know some exist but I have yet to run across in person a plug in charger greater than 32 amps. Even if you assume 40 amps what's the issue? 40 X 1.25 = 50 amps. 50 amp breaker, 50 amp wire and 50 amp receptacle.

 

[retirede]

California just follows the NEC. Nothing special here.

I know some exist but I have yet to run across in person a plug in charger greater than 32 amps. Even if you assume 40 amps what's the issue? 40 X 1.25 = 50 amps. 50 amp breaker, 50 amp wire and 50 amp receptacle.

Some of the most popular EVSEs are Chargepoint, Emporia, Grizzl-e, and JuiceBox. All capable of 40A on a 14-50. I’m surprised you haven’t seen one.

 

[electrofelon]

The receptacle, the OCPD, and the conductors (75° C) are all 50 amps. If the equipment is a continuous load and it is over 40 amps would you agree that it cannot have a 50 amp plug on it?

Let me "walk" thru this to see if I have it right: ,So lets say I have a 44 amp continuous load. So my wire and OCPD must be rated 55A. Say I install a 60 A OCPD and #6 NM. Good so far. Can I put a XX-50 recep at the end of this? If not what code section?

 

[ramsy]

Can I put a XX-50 recep at the end of this? If not what code section?

That depends if receptacle terminals are listed for your aluminum SE cable, at continuous 75C ?

This forum has reported several meltdowns of receptacles on car chargers.

Meltdowns not even Art.100 defined as continuous use, since Level 2 charger current cycles - graph-1 and graph-2

 

[infinity]

Let me "walk" thru this to see if I have it right: ,So lets say I have a 44 amp continuous load. So my wire and OCPD must be rated 55A. Say I install a 60 A OCPD and #6 NM. Good so far. Can I put a XX-50 recep at the end of this? If not what code section?

You cannot install the 50 amp receptacle on a 60 amp OCPD.

210.21(B) Receptacles.
210.21(B)(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

 

[electrofelon]

You cannot install the 50 amp receptacle on a 60 amp OCPD.

Ok thanks. But if we were to install 2 or more receps then we could?

 

[Sierrasparky]

California just follows the NEC. Nothing special here.

I know some exist but I have yet to run across in person a plug in charger greater than 32 amps. Even if you assume 40 amps what's the issue? 40 X 1.25 = 50 amps. 50 amp breaker, 50 amp wire and 50 amp receptacle.

The issue was not mine but a good friend and colleague I had a discussion with that said you cannot use #8 THHN for a 14-50 . We here agree.

 

[infinity]

The issue was not mine but a good friend and colleague I had a discussion with that said you cannot use #8 THHN for a 14-50 . We here agree.

We agree that you cannot use #8 then with a 14-50? It would be code compliant to use #8.

 

[ramsy]

We agree that you cannot use #8 then with a 14-50? It would be code compliant to use #8.

It's not just NEMA 14-50.

The extensive list of receptacles subject to the same UL 498 test standard, are shown in category (RTRT) of the White book.

See the complete list under HORSEPOWER RATINGS FOR NEMA CONFIGURATION RECEPTACLES.