EGC conductor question

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
I am in damage control mode in a situation where a conduit was run under a concrete sidewalk for an EV charging pedestal without consulting the designer (me) on what size it needs to be, so (of course) it is too small. It's not much too small; what would make enough difference in the conduit fill would be if we could run the EGC in bare wire direct buried outside the conduit along side the sidewalk to the pedestal. Will the code allow that?
 
I'll be very interested to see what the experts here say, that's a good question. What code cycle is the project under? I'm still under 2017 NEC, I went first to 250 and cruised through. What stands out to me that may be applicable is 250.134 (B) Exception No. 1: As provided in 250.130(C), the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.
 
winnie said:
How far away from the conduit would the EGC be? What is the material of the conduit?

-Jon
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The conduit is mostly PVC40 with PVC80 where it penetrates grade. It' is buried 18" or 24" deep down the center of the sidewalk, so I estimate ~36". Can I use 250.134 Exception No. 1 to justify it?
 
Joe.B said:
I'll be very interested to see what the experts here say, that's a good question. What code cycle is the project under? I'm still under 2017 NEC, I went first to 250 and cruised through. What stands out to me that may be applicable is 250.134 (B) Exception No. 1: As provided in 250.130(C), the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.
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I was typing when your response came in; this project is under the 2020 NEC; the article refeence is a little different but I have the same question.
 
ggunn said:
I am in damage control mode in a situation where a conduit was run under a concrete sidewalk for an EV charging pedestal without consulting the designer (me) on what size it needs to be, so (of course) it is too small.
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How about the details on that?

ggunn said:
It's not much too small; what would make enough difference in the conduit fill would be if we could run the EGC in bare wire direct buried outside the conduit along side the sidewalk to the pedestal. Will the code allow that?
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If you're running it alongside the sidewalk, direct buried, why use bare wire, rather than insulated?

ggunn said:
Can I use 250.134 Exception No. 1 to justify it?
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Definitely not, as that references 250.130(C), which is "(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions." Would not apply to a new branch circuit.

Cheers, Wayne
 
BTW, if the underground Sch 40 is large enough for a bare EGC, and it's just the Sch 80 portions that are the problem, would it be allowable to upsize just the Sch 80 portions? E.g. is it permitted to run conduit as, say, Box -> 1" Sch 80 -> 3/4" Sch 40 -> 1" Sch 80 -> Box?

Cheers, Wayne
 
ptonsparky said:
I would be inclined to replace the conduit with proper size if I need to expose it anyway. Depends on who is paying for the PVC. YIKES!
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It's not the conduit replacement but the jackhammering up of the sidewalk that I am trying to avoid.
 
250.134 Exc 1 points back to 250.130, which is about grounding previously allowed ungrounded receptacles or extending previously allowed ungrounded branch circuits. So that code doesn't apply.

About the only stretch that I can imagine is that you are permitted to have isolated phase installations underground in non-metallic conduit. So having an EGC outside of a PVC conduit underground arguably qualifies as 'otherwise run with circuit conductors'.

Presumably there is sufficient room in the bulk of the conduit run (SCH 40), but the conduit is undersized at the grade penetrations (SCH 80).
Have you run your conduit fill calculations considering a bare EGC?

Since you are already stuck with digging a trench to install the EGC, it is probably simplest to run a properly sized conduit and install all the conductors in it.

-Jon
 
wwhitney said:
BTW, if the underground Sch 40 is large enough for a bare EGC,...

Cheers, Wayne
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That's something I hadn't thought of. I'll have to run the calc by hand because the on line calculator doesn't have bare wire as an option.
 
winnie said:
About the only stretch that I can imagine is that you are permitted to have isolated phase installations underground in non-metallic conduit. So having an EGC outside of a PVC conduit underground arguably qualifies as 'otherwise run with circuit conductors'.
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There are three of these EV charger pedestals, each of which have two phases of 208 with no neutral.
 
All three chargers sharing the same conduit?

Can these chargers run L-N on a 208/360V or 240/416V system?

Have the conductors been pulled?

-Jon
 
ggunn said:
That's something I hadn't thought of. I'll have to run the calc by hand because the on line calculator doesn't have bare wire as an option.
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It's easy with the tables in the back of the NEC; if you had provided the details requested, any one here could do it.

Cheers, Wayne
 
winnie said:
All three chargers sharing the same conduit?

Can these chargers run L-N on a 208/360V or 240/416V system?

Have the conductors been pulled?

-Jon
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Each pedestal has two 40A chargers. There is a load center in the bulding that has six 50A breakers, two each on two phases of 208V; the panel is fed by a 480/277V delta to 208/120V wye transformer. Nothing is built yet except for the three undersized conduits under the sidewalk.
 
tortuga said:
If I were an inspector I'd rather see a slightly overfull pipe than an EGC ran separate from the circuit conductors.
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Moot point. I cannot stamp a drawing set that has an intentional code violation.
 
Since nothing is wired yet have you looked at running the 480 out there and putting the transf at the chargers or getting 480v chargers
 
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