1200 amp service in 2- 4" conduits?

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millspgh

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I have a client who has an existing 800 amp service, being fed by 2- 4" conduits, they want to know if there is any scenario which they can get a 1200 amp service fed with 2- 4" conduits.
The distance from service to utility pole is about 175'.

I believe you can put 5- 600mcm in a 4" conduit, and 4- 700mcm in a 4", but that's before derating. Does anybody see a scenario where they can upgrade this service to 1200 amps without adding or replacing the existing underground conduits?

Thank you
 
augie47

augie47

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Tennessee
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State Electrical Inspector (Retired)
Devil is in the details... what is your calculated load on the phases and neutral and is it predominately linear or non-linear ? Is there a main or is it MLO ?
Your (5) 600s per conduit might be sufficient.
 
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millspgh

Member
augie47 said:
Devil is in the details... what is your calculated load on the phases and neutral and is it predominately linear or non-linear ? Is there a main or is it MLO ?
Your (5) 600s per conduit might be sufficient.
Click to expand...

I do not know the load.
There is a main breaker in the MDP, and possibly a main disconnect before the mdp. Nothing outside though in before or after the CT cabinet.
 
augie47

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
opps my error. I was looking at the # of conductors and forgot each conduit must contain all phases..
 
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millspgh

Member
augie47 said:
opps my error. I was looking at the # of conductors and forgot each conduit must contain all phases..
Click to expand...

I don't see anyway this can happen, even using 700mcm copper, if you could get 4 conductors in, you still fall short of 1200a. I am just waondering if maybe I am missing some option that would allow it.

There were suppose to be 2 spare 4" conduits put in this service when the building was built 5 years ago, they were not put inh by that contractor. now its time for the new addition, and they realize they do not have the conduits to upsize their service.
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Ok, main breaker so you need the full 1200 amps. Assuming 4" schedule 40, and neutral not a CCC:

2 sets of 400 Copper in each pipe. Thats 8 conductors total, 6 CCC, 80% derating, 380X.8=304 per set. Meets fill. If neutral is a CCC, will still work with 500 and 70% derating. Have fun. Tell me what day you are doing it, and Ill make sure to turn my phone off, or otherwise not be available ;)
 
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winnie

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Location
Springfield, MA, USA
Occupation
Electric motor research
The devil is in the details here.

1) What kind of 4" conduit do you have? The interior cross section is different for different conduit types. There is a 30% difference in area between sch 80 PVC and EMT for the extremes.

2) Do you need a full size neutral? Is the neutral a CCC?

3) Can you get compact stranded _copper_ conductors?

My guess: getting 1200A through 4" conduit is possible, for some values of 4" and some values of 1200 :)

-Jon
 
tkb

tkb

Senior Member
Location
MA
electrofelon said:
Ok, main breaker so you need the full 1200 amps. Assuming 4" schedule 40, and neutral not a CCC:

2 sets of 400 Copper in each pipe. Thats 8 conductors total, 6 CCC, 80% derating, 380X.8=304 per set. Meets fill. If neutral is a CCC, will still work with 500 and 70% derating. Have fun. Tell me what day you are doing it, and Ill make sure to turn my phone off, or otherwise not be available ;)
Click to expand...

I agree with the 2 sets of 400cu per conduit.
If you wanted to use 500cu you can only fit 7 in the 4".
You might be able to use 500cu if you can reduce the neutrals.
 
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