Ev charger wire and ocpd sizing

[wc86]

Looking to install a 50a EV charger. If i get 62.5a after multiplying by 1.25 for continous load, does that mean I can use #6 thhn with a 70a breaker for this with the next size up rule or do i need to run #4 wire with the 70a breaker?

 

[Elect117]

No.

Your conductor needs to be sized for the continuous rating of the load. If you are saying that the charger is truly rated 50A of load, and multiplying by the continuous rating is 62.5A, then you should run #4 copper and install a 70A breaker. (625.41)

The exception is if you can limit the load on the device in a way described in 625.42.

 

[wwhitney]

Looking to install a 50a EV charger.

EVSEs are sometimes marketed based on the circuit size required, rather than the continuous current provided. An EVSE that provides 50A continuous would be a bit unusual, so as 125% * 50A is not a standard breaker size. So are you sure you don't have a 40A EVSE that requires a 50A circiut?

If i get 62.5a after multiplying by 1.25 for continous load, does that mean I can use #6 thhn with a 70a breaker for this with the next size up rule

Yes if using a 75C rated wiring method, as then #6 Cu is rated for 65A which suffices. No if you are restricted to the 60C ampacity of 55A for some reason, like using LFNC outdoors.

Cheers, Wayne

 

[wc86]

EVSEs are sometimes marketed based on the circuit size required, rather than the continuous current provided. An EVSE that provides 50A continuous would be a bit unusual, so as 125% * 50A is not a standard breaker size. So are you sure you don't have a 40A EVSE that requires a 50A circiut?


Yes if using a 75C rated wiring method, as then #6 Cu is rated for 65A which suffices. No if you are restricted to the 60C ampacity of 55A for some reason, like using LFNC outdoors.

Cheers, Wayne

Yes im allowed to use a #6thhn thats rated for 65amps @ 75°c on a 70amp breaker?

 

[jaggedben]

Yes im allowed to use a #6thhn thats rated for 65amps @ 75°c on a 70amp breaker?

Yes, if no derating is required, e.g. for temperature.

But I suspect you have an EVSE that either supports a current of 40A and would go on a 50A breaker, or that supports 48A and would go on a 60A breaker. They do it that way to correspond to breaker sizes. As Wayne said, an EVSE with an actual max current of 50A would be unusual.

 

[Elect117]

Just be careful using the 75°C column on conductors less than 100A

UL AALZ

"Except as noted in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C insulated conductors in circuits rated 100 A or less, and the use of 75°C insulated conductors in higher rated circuits as specified in Table 310.15(B)(16) of the NEC. If the termination provisions on equipment are based on the use of other conductors, the equipment is either marked with both the size and temperature rating of the conductors to be used or with only the temperature rating of the conductors to be used. If the equipment is only marked for use with conductors having a higher (75 or 90°C) temperature rating (wire size not specified), the 60°C ampacities (for circuits rated 100 A or less) and 75°C ampacities (for circuits rated over 100 A) should be used to determine wire size.

Basically if the termination or device is not marked for both the 75°C rating AND the wire size UL says to still use the 60° rating.

"Except as noted in the following paragraphs or in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C ampacities for wire size Nos. 14-1 AWG, and 75°C ampacities for wire size Nos. 1/0 AWG and larger, as specified in Table 310.15(B)(16) of the NEC."

And for circuit breakers:
"A 75°C conductor temperature marking on a circuit breaker or switch normally intended for wire sizes 14-1 AWG does not in itself indicate that 75°C insulated wire can be used unless 1) the circuit breaker or switch is used by itself, such as in a separate enclosure, or 2) the equipment in which the circuit breaker or switch is installed is also so marked."

You shouldn't use the 75°C rating unless the wire size is 1/0 or larger (generally speaking).

 

[wc86]

Yes, if no derating is required, e.g. for temperature.

But I suspect you have an EVSE that either supports a current of 40A and would go on a 50A breaker, or that supports 48A and would go on a 60A breaker. They do it that way to correspond to breaker sizes. As Wayne said, an EVSE with an actual max current of 50A would be unusual.

I dont know. It's a chargepoint hardwired version and it says 50a max

 

[Elect117]

Regardless, the product installation guide most likely says the suggested breaker and wire size.

 

[wc86]

The terminals seem to be rated 100°c and only accept #6 max. So im glad this is working out to staying with #6 thhn lol

 

[retirede]

The ChargePoint Homeflex can, indeed, be configured to charge at 50A, but you don’t have to use it at its full capacity. I would configure it for 48A on a 60A circuit.

 

[Elect117]

The terminals seem to be rated 100°c and only accept #6 max. So im glad this is working out to staying with #6 thhn lol

You might want to double check that. You have to consult the product sheet of the charger but also the breaker and panelboard.

As far as I know there no switchgear or panelboard manufacturer that is rated above 75°C.

 

[Elect117]

The ChargePoint Homeflex can, indeed, be configured to charge at 50A, but you don’t have to use it at its full capacity. I would configure it for 48A on a 60A circuit.

"Consult applicable codes for breaker and wire sizing requirements"

You might have to use 310.14(A)(2) Exception and splice in a larger size conductor like #4 in a box within 10' or 10% of the load.

"
Exception:
Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit."

Assuming you are going with the max load of 50A in the table on the second page of retirede's post.

 

[tortuga]

No if you are restricted to the 60C ampacity of 55A for some reason, like using LFNC outdoors.

LFNC is not rated 90C?

 

[don_resqcapt19]

Just be careful using the 75°C column on conductors less than 100A

UL AALZ

"Except as noted in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C insulated conductors in circuits rated 100 A or less, and the use of 75°C insulated conductors in higher rated circuits as specified in Table 310.15(B)(16) of the NEC. If the termination provisions on equipment are based on the use of other conductors, the equipment is either marked with both the size and temperature rating of the conductors to be used or with only the temperature rating of the conductors to be used. If the equipment is only marked for use with conductors having a higher (75 or 90°C) temperature rating (wire size not specified), the 60°C ampacities (for circuits rated 100 A or less) and 75°C ampacities (for circuits rated over 100 A) should be used to determine wire size.

Basically if the termination or device is not marked for both the 75°C rating AND the wire size UL says to still use the 60° rating.

"Except as noted in the following paragraphs or in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C ampacities for wire size Nos. 14-1 AWG, and 75°C ampacities for wire size Nos. 1/0 AWG and larger, as specified in Table 310.15(B)(16) of the NEC."

And for circuit breakers:
"A 75°C conductor temperature marking on a circuit breaker or switch normally intended for wire sizes 14-1 AWG does not in itself indicate that 75°C insulated wire can be used unless 1) the circuit breaker or switch is used by itself, such as in a separate enclosure, or 2) the equipment in which the circuit breaker or switch is installed is also so marked."

You shouldn't use the 75°C rating unless the wire size is 1/0 or larger (generally speaking).

It is very rate to see new equipment that does not have terminations suitable for use with the 75°C ampacities.

 

[wwhitney]

Basically if the termination or device is not marked for both the 75°C rating AND the wire size UL says to still use the 60° rating.

My understanding is that the markings work like this:

60C - use at least 60C insulation at the 60C ampacity
75C - use at least 75C insulation at the 60C ampacity
60C/75C - use either 60C insulation at the 60C ampacity or 75C insulation at the 75C ampacity

And I believe that matches the section you quoted, although that text was not as clear as it could be.

Cheers, Wayne

 

[wwhitney]

LFNC is not rated 90C?

Per UL 1660 Section 6.1.3(d), LFNC may have an 80C, 90C, or 105C dry location rating and is to be so marked. Per Section 6.1.3(g), the wet location rating is always 60C, and marking that is therefore optional.

IIRC, LFMC is similar.

Cheers, Wayne

 

[Elect117]

What you said is correct to me.

The white page from UL is here:

https://code-authorities.ul.com/wp-content/uploads/2014/09/UL-White-Book.pdf

Molded Case Circuit Breaker - Marking and Application Guide | UL Solutions Code Authorities

UL Marking and Application Guide for molded case circuit breakers and related hardware.

code-authorities.ul.com

Eaton's guide:

https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/solution-center/bus-ele-tech-lib-conductor-ampacities.pdf

UL's guide is not a fun or easy read. It also disagrees with the NEC where it says the 75°C rating used on wires of 1/0 or larger and the NEC says #1 or larger.

I had a disagreement a little while back with another engineer about it. We came to the following consensus (and this might extend past what the OP posted).

In a simple system, you have the panelboard connected to the breaker, connected to the wire, connected to a termination connected to the load.

Or there is another termination in the panelboard when there is no breaker.

In any case, everything must be labeled 75°C. The enclosure, the breaker, the wire, the terminations, etc. And the terminations must also be labeled with the wire size. If it doesn't include the wire size then the lower temperature shall be used.

Nothing is rated 90°C except for wire and terminations. Panelboards, breakers, etc. are not tested by UL at anything higher than 75°C. Crazy enough that they don't. To me it sounds like a simple win on the manufacturer to get that product stamp on high ampacity switchgear.

No equipment is rated for free air. As soon as a conductor enters a switchgear it is no longer free air rated. As soon as the conductor touches a breaker, it is no longer free air rated. Even if the whole assembly is exposed in free air. And debatably, and this is still something I haven't been able to confirm, but terminations on bus duct are not allowed to use the free air rating because the component parts enter enclosed switchgear.

 

[wwhitney]

And the terminations must also be labeled with the wire size. If it doesn't include the wire size then the lower temperature shall be used.

I don't think I believe that part, as it's not in the NEC. Otherwise I agree.

Cheers, Wayne

 

[wwhitney]

"Except as noted in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C insulated conductors in circuits rated 100 A or less, and the use of 75°C insulated conductors in higher rated circuits as specified in Table 310.15(B)(16) of the NEC. If the termination provisions on equipment are based on the use of other conductors, the equipment is either marked with both the size and temperature rating of the conductors to be used or with only the temperature rating of the conductors to be used. If the equipment is only marked for use with conductors having a higher (75 or 90°C) temperature rating (wire size not specified), the 60°C ampacities (for circuits rated 100 A or less) and 75°C ampacities (for circuits rated over 100 A) should be used to determine wire size.

OK, this excerpt from UL AALZ Guide Info is under the section "Appliance and Utilization Equipment Terminations." So if it is to be believed, it would not apply to breakers, devices, or EVSEs, just to appliances and utilization equipment.

Cheers, Wayne

 

[wwhitney]

75C - use at least 75C insulation at the 60C ampacity

Actually, I'm not finding any support for this idea in the UL category info or in the application guide https://code-authorities.ul.com/molded-case-circuit-breaker-marking-and-application-guide/

I think if the breaker is marked just "75C" you must use at least 75C rated insulation, but get to use the 75C ampacity.

Cheers, Wayne