Tesla 32A Outlet with 50A Circuit?

[NoahsArc]

I would assume a 32A mobile plug-in charger wouldn't need more than a 40A breaker, based on the code. Yet despite already being +25% per code at 40A for continuous load, Tesla is recommending to bump that another +25% to 50A. I can't really tell if this is a manufacturer requirement or a recommendation based on this link of theirs. What are your esteemed thoughts on this? For a short run, it makes like 5% cost difference, but for a 40+ ft run it would be a serious cost increase.

Is it required per this language (and I guess then NEC would say follow the manufacturer)? Would you do so if it wasn't a hard requirement?

 

[xformer]

The verbology of the document reads "The recommended home charging installation...." not "The required home charging installation."

 

[Elect117]

That is normal. The receptacle is not rated for the continuous use of 50A. It is rated for the continuous use of 40A. (40*1.25 = 50). They are spelling out the need for #6 Cu on a 50A receptacle / 50A breaker as a means to always be code compliant with 60°C terminals.

NEMA is investigating their 14-50 Receptacles for melting due to external heat, continuous use at rated current and breaker trip curves not protecting them prior to melting. I would air on the side of reducing the effects of temperature when you can.

If installing a 14-50 receptacle it is a code requirement that the circuit rating protects it. So, if you are planning on putting a 14-50 plug that only draws 1 Amp you still need have a 50A breaker, 50A of wire. See 210.18, 210.19(A)(1)(b) and 210.21(B)(1). Also see 625.40/625.41/625.42. The maximum load to be served is the receptacle rating. The branch circuit can not have a rating less than that.

 

[infinity]

If installing a 14-50 receptacle it is a code requirement that the circuit rating protects it. So, if you are planning on putting a 14-50 plug that only draws 1 Amp you still need have a 50A breaker, 50A of wire

That is incorrect. A 50 amp single receptacle is permitted on an individual branch circuit with an OCPD/conductors less than 50 amps. For example for a 40 amp range circuit uses a 50 amp single receptacle with a 50 amp cord and plug.

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.

 

[NoahsArc]

That is normal. The receptacle is not rated for the continuous use of 50A. It is rated for the continuous use of 40A. (40*1.25 = 50). They are spelling out the need for #6 Cu on a 50A receptacle / 50A breaker as a means to always be code compliant with 60°C terminals.

NEMA is investigating their 14-50 Receptacles for melting due to external heat, continuous use at rated current and breaker trip curves not protecting them prior to melting. I would air on the side of reducing the effects of temperature when you can.

If installing a 14-50 receptacle it is a code requirement that the circuit rating protects it. So, if you are planning on putting a 14-50 plug that only draws 1 Amp you still need have a 50A breaker, 50A of wire. See 210.18, 210.19(A)(1)(b) and 210.21(B)(1). Also see 625.40/625.41/625.42. The maximum load to be served is the receptacle rating. The branch circuit can not have a rating less than that.

Not following.
The receptacle is rated for the continuous use of 40A, and it is receiving the continuous use of 32A. 60C column says 40A is okay on #8.
Every 14-50R I've seen is 75C anyway, even the cheap Leviton, and even 50A #8 @75C is fine for a continuous 40A draw.

Regarding a 50A receptacle on a 40A circuit: I agree with inifinity's assessment of the code you cited.

 

[NoahsArc]

The verbology of the document reads "The recommended home charging installation...." not "The required home charging installation."

That's it basically I guess, but I do wonder why they felt the need to recommend another 25%... I had a client question me on this today when I said I'd pull #8s. I increased the quote appropriately to satisfy them

 

[Elect117]

That is incorrect. A 50 amp single receptacle is permitted on an individual branch circuit with an OCPD/conductors less than 50 amps. For example for a 40 amp range circuit uses a 50 amp single receptacle with a 50 amp cord and plug.

You are correct. I misread it. The OCPD decides the branch circuit rating. I initially read it to be the receptacle which is incorrect. The OCPD can not be larger than the receptacle rating.