SparksWillFly
Member
- Location
- Connecticut
- Occupation
- Licensed Electrician
Reposting this here for more visibility
tldr: does NEC 625.41 apply to field-installed DC conductors on EVSE?
With EV charging there are manufacturers that sell a DC fast charger in 2 pieces. An AC-DC rectifying cabinet and a DC charging pedestal. The manufacturer does not supply the DC wires that interconnect the equipment and they do not instruct you on how to calculate. They simply give you the maximum ampacity and wire size that can be used. Looking for insight on a discussion that has come up about if NEC 625.41 is applicable to this calculation of DC conductors.
From my interpretation, the equipment is considered continuous duty and it shouldn't matter if it's the AC coming in or the DC branch circuit is going out. It's a circuit related to EVSE and should be sized at 125% of the max amps.
Because this is something installed in the field, wouldn't it also fall out of any UL listings? As in, the manufacturer can't advise that the 125% calculation isn't necessary because it's not within their jurisdiction. If they want to control the DC wire size it needs to be a part of their UL stamped product.
Parameters to work with:
Max DC amps output from rectifier: 500a
Max wire size: 4/0
Conduit: 1- 4 inch
Conductors on each terminal (negative and positive) - 3
350a x 125% = 437.5a (is what the conductors should be rated for)
4/0 XHHW-2 rated at 260a x 3 = 780a
Derate for 6 current carrying conductors in a conduit - 780 x 80% = 624a
No derating for ambient temp
tldr: does NEC 625.41 apply to field-installed DC conductors on EVSE?
With EV charging there are manufacturers that sell a DC fast charger in 2 pieces. An AC-DC rectifying cabinet and a DC charging pedestal. The manufacturer does not supply the DC wires that interconnect the equipment and they do not instruct you on how to calculate. They simply give you the maximum ampacity and wire size that can be used. Looking for insight on a discussion that has come up about if NEC 625.41 is applicable to this calculation of DC conductors.
From my interpretation, the equipment is considered continuous duty and it shouldn't matter if it's the AC coming in or the DC branch circuit is going out. It's a circuit related to EVSE and should be sized at 125% of the max amps.
Because this is something installed in the field, wouldn't it also fall out of any UL listings? As in, the manufacturer can't advise that the 125% calculation isn't necessary because it's not within their jurisdiction. If they want to control the DC wire size it needs to be a part of their UL stamped product.
Parameters to work with:
Max DC amps output from rectifier: 500a
Max wire size: 4/0
Conduit: 1- 4 inch
Conductors on each terminal (negative and positive) - 3
350a x 125% = 437.5a (is what the conductors should be rated for)
4/0 XHHW-2 rated at 260a x 3 = 780a
Derate for 6 current carrying conductors in a conduit - 780 x 80% = 624a
No derating for ambient temp
