4000A Parallel run feeders

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WattsOn70

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I need to provide an underground supply from the utility transformer to a 4000A, 208/120V main switchgear, of a new construction hotel.

As of engineered drawings, the service should be provided with 10 sets of 600KCM parallel runs, CU.

Q: Considering none of both wire ends connect to OCP, but to termination lugs at XFMR side, and bus bars at main gear pulling section,
can I run 9 sets of 600KCM or maybe 10 sets of 500KCM instead? and save some $$ in copper.
or maybe better run 10 sets of 700KCM AL?

cable pulls are about 250ft

Jorge
 

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Considering the Engineered drawings show 10 sets, what does your re-engineered Neher McGrath calculations show for ampacity for the underground feeders if it is less than 10 sets of 600's?
 
WattsOn70 said:
Considering none of both wire ends connect to OCP, but to termination lugs at XFMR side, and bus bars at main gear pulling section,
can I run.......
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I am not following you reasoning with this statement of why this would allow you to use less than 4000A of conductor. Unless you are proposing to use the 90 degree ampacity column? I doubrt your equipment is rated for 90 degree terminations, even if the conductors dont land directly on an OCPD.

None of you proposed combinations would provide at least 4000A at 75 degree C. IF you are not on the 2020 NEC and have multiple mains, then you could size you conductors to the load calc.

I would definitely explore AL conductors as a cost saving measure but you would probably need this change approved.
 
Just trying to get a better understanding here. If the ten sets of copper were on the prints and that’s what your price was based on why switch it up. Are you looking out for the owner and plan to issue a change order credit? If your working up front on VE effort, that makes sense.
Side note, this is the service range, where depending on what the utility thinks about the load and there diversity factors for that type of building, They could give you a transformer size that can’t accommodate that many sets and you will need to have sectionalizing cabinet that you go to. Maybe even issues at switchgear. I like to do even number of sets in this situation in case you need to split it up between 2 2000A mdp or something, because the 4000 amp gear will take two years to get there, half kidding. Looks like it wouldn’t matter here but sometimes copper is needed to keep the sets down to accommodate that transformer limits.
If your going for it, In lieu of the calcs atleast look at the duct bank derating, not sure if the NEC still has those only tied to medium voltage, from why I recall. I think it’s still a good check.
 
I'm in line with Post #3. Since duct banks are involved and you have engineered drawings I doubt any deviation your be approved by the AHJ without a P.E. drawing.
 
If you're looking to save money then use Aluminum. I don't see how you can use less than 4000 amps worth of conductors so it's 10 sets of 600 kcmil if you go with copper. 700 kcmil is not a size that is readily available around here so for us it would be 11 sets of 750 kcmil aluminum (385*11=4235 amps). Why do engineers continue to specify running an EGC with service conductors?
 
infinity said:
If you're looking to save money then use Aluminum. I don't see how you can use less than 4000 amps worth of conductors so it's 10 sets of 600 kcmil if you go with copper. 700 kcmil is not a size that is readily available around here so for us it would be 11 sets of 750 kcmil aluminum (385*11=4235 amps). Why do engineers continue to specify running an EGC with service conductors?
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The local utilities here limit us to a maximum of 10 sets, so he would need to check with his utility, as well as getting the change approved by the design engineer.
 
Thank you for all your inputs.
I was only wondering if there was a chance to use 90 D rated wires instead, based on the fact that wires are not landing right on the OCPD, but on terminal lugs rated 90 D.
Actually, as 240.4 (C), service can't be greater than OCPD rated >800A.

The G wires were already revised by PE and removed from the runs. Also, the plan is in fact use AL conductors.
 
WattsOn70 said:
Thank you for all your inputs.
I was only wondering if there was a chance to use 90 D rated wires instead, based on the fact that wires are not landing right on the OCPD, but on terminal lugs rated 90 D.
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My understanding is that even if you land on 90 degree lugs that are on a busbar some distance from the OCPD you are still stuck with what the listing/rating provided by the manufacturer is and I believe that will still be 75. Let us know if the manufacturer allows 90 degree terminations.
 
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