Electrician Talk banner
1 - 17 of 17 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
I am trying to figure out if I can run 2 X 200A sub feeders in the same 4" PVC underground conduit.
NEC 310 is not clear to me. Am I allowed to run the conductors in the same conduit.
There is a new 1P 600A standup going in and the home owner has previously ran with this remodel in mind a 4" conduit from the new switchgear to the sub panel locations. Can I run the conductors in parallel assuming a separate neutral and ground for each sub panel or do I need 2 separate conduits?
 

·
Banned
I make all the electrons line up for their Flu shots
Joined
·
33,456 Posts
To be clear, they are ''sub'' panels and the feeders are protected by overcurrent and downstream of the ''service disconnect'' right? Then it is ok as long as conduit fill is properly accounted for and proper burial depth if buried underground.
 

·
Registered
Joined
·
1,622 Posts
Derating the conductor ampacities must be allowed for. Does each subfeed circuit have individual overcurrent protection? If not, most places would not allow this install. Some jurisdictions will allow a service, say 400 amp, to split to two 200 amp panels. Different rules apply to feeders though.
 

·
Retired Account
Joined
·
39,697 Posts
Is going from T310.15(B)(7) {dwelling service & feeders} to T310.15(B)(3)(a) {derating to 80% for 4-6} by way of T310.15(B)(16) {former 310.16} the issue?

~CS~
 

·
Administrator
Retired EC
Joined
·
23,672 Posts
I am trying to figure out if I can run 2 X 200A sub feeders in the same 4" PVC underground conduit.
NEC 310 is not clear to me. Am I allowed to run the conductors in the same conduit.
There is a new 1P 600A standup going in and the home owner has previously ran with this remodel in mind a 4" conduit from the new switchgear to the sub panel locations. Can I run the conductors in parallel assuming a separate neutral and ground for each sub panel or do I need 2 separate conduits?
You can run it in one conduit but you must derate as stated by Steve in the post above. You could also run a larger conductor suitable for 400 amps and then tap to the 200 amp panels.

Not sure why the homeowners get a voice in this
 
  • Like
Reactions: pete87

·
Registered
Joined
·
3 Posts
Discussion Starter · #6 ·
Yes Mac,

Both circuits are protected by a separate 200A disconnect at the stand up, Sub panels are MLO.

Engineer is calling for 500 MCM-AL and #4 ground. But has it in separate 4" conduits and there is already a provisioned a 4" but would have to tear up existing driveway to run additional conduit,
 

·
Administrator
Retired EC
Joined
·
23,672 Posts
Is distance a factor. Certainly you don't need 500 kcm if they are in 2 conduits-- heck depending on the load 4/0 alum or 250 kcm is all that is needed if separate conduits are used.

If you run both feeders in one conduit then you need to derate. Assuming 75C 500kcm is more than you need also-- 350 kcm should work.

Now if these are approved plans then you may be required to do as the engineer drew it unless you can get him to change it officially.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #8 ·
I think distance is a factor. I just got the site plan and will have to get a full size sheet made to scale the distance. It looks pretty far. that would be why the 500 MCM. I think the engineer is used to doing commercial not residential.

He is asking in the notes for a NTRL cert of for the service ground fault protection. Yet the disconnect specified is a fused switch and does not offer ground fault protection. Normally I see this request for 1000A and above.

Will have to do the math on the derating of the conductors to see if Vdrop is the issue for the size. The conduit will hold that many conductors but might be to hard to actually pull.

Appreciate all the input.

Love the response here.

Thanks again
 

·
Registered
Joined
·
2 Posts
Sometimes running copper conductors in this situation might resolve an issue with existing conduit size/wire size/ and VD. The issue then becomes cost increase which can be advantageous to an EC if they approach the owner in the right way.

P.S.
Don't be afraid to make money.
 

·
Banned
Joined
·
1,486 Posts
Yes Mac,

Both circuits are protected by a separate 200A disconnect at the stand up, Sub panels are MLO.

Engineer is calling for 500 MCM-AL and #4 ground. But has it in separate 4" conduits and there is already a provisioned a 4" but would have to tear up existing driveway to run additional conduit,



Come on mate , you gonna let that Drive Way Win ?



Pete
 

·
Electrical Contractor
Joined
·
9,325 Posts
I think distance is a factor. I just got the site plan and will have to get a full size sheet made to scale the distance. It looks pretty far. that would be why the 500 MCM. I think the engineer is used to doing commercial not residential.

He is asking in the notes for a NTRL cert of for the service ground fault protection. Yet the disconnect specified is a fused switch and does not offer ground fault protection. Normally I see this request for 1000A and above.

Will have to do the math on the derating of the conductors to see if Vdrop is the issue for the size. The conduit will hold that many conductors but might be to hard to actually pull.

Appreciate all the input.

Love the response here.

Thanks again
Are you talking Ground Fault protection or Fault Current protection? Two different things.
 

·
Registered
Joined
·
55 Posts
Hippie said:
how is that any different than say (2) 20A circuits from the same panel to a garage? i may be wrong, ive just never heard of doing it like that.. i would think maybe a single 400a feeder and tap the 2 panels from that
I agree completely, I was just helping sort out the 2 separate feeders confusion.
 
1 - 17 of 17 Posts
Top