philsoma
Member
- Location
- Brighton, Michigan
I'm using 6/2 CU for an ev charger that specifies a 60 cb but uses 48 amps (80% rule?). my problem is, the 6/2 cable is rated for 55 amps. Is 60 ok?
6/2 CU cable: 60amp cb?
- Thread starter philsoma
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Isn't the conductor required to be sized at 125% of 48 amps? If so you need a 60 amp minimum conductor.
philsoma
Member
- Location
- Brighton, Michigan
No CU SE cable available. Must use copper.
There are a few supply houses around here that suffer from the "If I never herd of it they must not make it I cant be bothered to look" plague.
You can get copper SE down to #8 from some manufacturers but its a large minimum order.
You can get copper SE down to #8 from some manufacturers but its a large minimum order.
Use AL conductors to a junction point. Proceed with CU into the device.
philsoma
Member
- Location
- Brighton, Michigan
I thought there was a rule of thumb that if the ampacity is not matched by an available breaker size, that you can bump up to the next size. BTW SE CU isn't available around here.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Not a rule of thumb, but an actual allowance. If a common sized OCPD is not made that matches the load, you are allowed to go to the next size OCPD. However the load can't go over the size the conductor is rated for. In the case of NM 6-2, you could use a 60A breaker but the load can't be over 55A.
letgomywago
Senior Member
- Location
- Washington state and Oregon coast
- Occupation
- residential electrician
You can order 6 seu copper online or another option is 4 AL SE to an ac disconnect then copper 6 thhn in conduit to the charger
philsoma
Member
- Location
- Brighton, Michigan
The load is rated as 48 amps. The Ford installation book calls for a 48amp continuous load on a 60 amp cb. So I'm good with the 60amp cb on the 6/2 CU Romex that's rated at 55amps.
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
NO!!! 48 amps continuous = 60 amps. 6/2 NM cable is only rated for 55 amps. You need to use a conductor with an ampacity of 60 amp or greater.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
I agree that's what the NEC says in 210.19(A)(1)(a).
But the rule makes no sense for this situation, at 60C the #6 Cu is rated to carry 55A continuously, so there is no issue with it carrying only 48A continuously. And 240.4(B) says it's fine to protect 60C #6 Cu with a 60A OCPD for a non-continuous 55A load, and the #6 Cu will be equally well protected when the load is only 48A, rather than 55A.
Cheers, Wayne
Last edited:
philsoma
Member
- Location
- Brighton, Michigan
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
And unless you are brainwashed that it is not acceptable you can use the raceway as the EGC.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Minimum ampacity required is 125% of 48 = 60.
If you have or must consider your conductor to be a 60C conductor 6 AWG is only a 55 amp conductor.
You can use 90C ampacity column for adjustments if those apply but absolute minimum conductor size is still based on 60C ampacity for termination temp reasons.
If you have at least 75C conductor you are fine as it's ampacity is over 60.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Yes, that's the part that makes no sense, as ampacity is a continuous rating. Minimum ampacity required for a 48A continuous load should be 48A.
Cheers, Wayne
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
For the record, what 80% rule?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The minimum conductor size required by the NEC is 60 amps. Find one that is rated for 60 amps or more and that's what you'll need to use. The fact that it makes no sense is irrelevant. 
- Status