Wire size for 400 amp service

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millspgh

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I need to give a price on a 400 amp, 3 phase 4 wire service, and I don't want to get burned by the derating issue. I was planning on running 4 500mcms in a 4" pvc pipe, the pipe will be about 100' long above a drop ceiling in a retail area. I know by having 4 current carrying conductors I need to derate, but I am not sure how to go about this, any help is appreciated.
 

wbalsam1

Senior Member
Location
Upper Jay, NY
millspgh said:
I need to give a price on a 400 amp, 3 phase 4 wire service, and I don't want to get burned by the derating issue. I was planning on running 4 500mcms in a 4" pvc pipe, the pipe will be about 100' long above a drop ceiling in a retail area. I know by having 4 current carrying conductors I need to derate, but I am not sure how to go about this, any help is appreciated.

It seems way too far for service conductors considered inside the building envelope. If you end up with feeders, will you need to include an equipment grounding conductor in the conduit as well?:) :-?
 

millspgh

Member
service

service

I know I will need an equipment ground also. I am sure th store will not need all 400 amps, but the panel will be a 400 amp main breaker panel
 

millspgh

Member
service

service

Also, this is coming from an outdoor fused disconnect on the outside of the building, which is fed from an outdoor trough that is fed from a 1200 amp switch outside.
 

1793

Senior Member
310.16...

310.16...

millspgh said:
I know I will need an equipment ground also. I am sure th store will not need all 400 amps, but the panel will be a 400 amp main breaker panel

Correct me if I'm wrong but according to Table 310.16 -- 500 CU is only rated at 380 amps at 70 deg.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
millspgh, I think you're confusing Feeders and Services. You should read 310.15(B) for whether the neutral will need to be counted as a Current Carrying Conductor.


Roger
 
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millspgh

Member
There are no blue prints, the owner of the shopping plaza asked me to give him a price on putting a 400 amp panel in a location a Family Dollar is moving into, fed from the outside of the building at a 4oo amp fused disconnect switch
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The 500's can be used if your connected load is 380 amps or less and protected at 400 amps. The neutral would have to have more than 50% of it's load as non-linear for it to count as a CCC.
 

millspgh

Member
My load will be much less than 380 amps, how do I check that neutral usage you just mentioned? I do appreciate everybodys input here, thank you.
 

Mike01

Senior Member
Location
MidWest
dollar store??

dollar store??

probally way off the topic. but a 400A service for a dollar store seems like alot to me..
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
millspgh said:
My load will be much less than 380 amps, how do I check that neutral usage you just mentioned? I do appreciate everybodys input here, thank you.


You would have to figure out what your harmonics loads are and how large they are. IMO in a store they wouldn't be a factor.
 

1793

Senior Member
Originally Posted by millspgh
I know I will need an equipment ground also. I am sure th store will not need all 400 amps, but the panel will be a 400 amp main breaker panel

1793 said:
Correct me if I'm wrong but according to Table 310.16 -- 500 CU is only rated at 380 amps at 70 deg.

I posted without reading carefully, I missed the "not" in the original post. Sorry
 
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