Conduit Fill / Derating

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Loffgren

Senior Member
Location
CA
Ok I have confussed myself to the point of no return. I need to run a 200 amp feed 300 feet.

single phase 240 volt

3 250kcmil cunductors and one #4 for ground. I Came up with 2 1/2" Emt.

After derating for more than 3 conductors in conduit, I feel i need to go up to 350kcmil

Help my head hurts
 
S

SEO

Senior Member
Location
Michigan
I'm not doing any calculations for you but if you look at section 310.15 (B) (2) (a) it says more than three current-carring conductors in a raceway or cable. Now look at 310.15 (B) (4)(a) and (5) you will see that a neutral conductor that carries only the unballanced current from the other conductors is not required to be counted. (5) a grounding or bonding conductor shall not be counted as well. Looks like you have two current- carring conductors.
 
C

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Derating plays no part in this, only when you have 4 or more current carrying conductors. You just need to do your fill calcs for whatever size wire you choose.

Make sure to keep your EGC sized proportional to your phases since they increased in size.
 
L

Loffgren

Senior Member
Location
CA
SEO said:
I'm not doing any calculations for you but if you look at section 310.15 (B) (2) (a) it says more than three current-carring conductors in a raceway or cable. Now look at 310.15 (B) (4)(a) and (5) you will see that a neutral conductor that carries only the unballanced current from the other conductors is not required to be counted. (5) a grounding or bonding conductor shall not be counted as well. Looks like you have two current- carring conductors.
Click to expand...

thank you.. that helps.
 
L

Loffgren

Senior Member
Location
CA
Cow said:
Derating plays no part in this, only when you have 4 or more current carrying conductors. You just need to do your fill calcs for whatever size wire you choose.

Make sure to keep your EGC sized proportional to your phases since they increased in size.
Click to expand...

thanks as well i will add up my cir mills..
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
250 CU or AL?

Are you concerned with voltage drop or not?

What is the real load?

It's hard to say what size conductor you might use without knowing more than its a '200 amp feed'

You might be able to run 4/0 AL, but 300' is a fairly long way you might need 350 CU it all depends on how much voltage drop you can live with.
 
L

Loffgren

Senior Member
Location
CA
iwire said:
250 CU or AL?

Are you concerned with voltage drop or not?

What is the real load?

It's hard to say what size conductor you might use without knowing more than its a '200 amp feed'

You might be able to run 4/0 AL, but 300' is a fairly long way you might need 350 CU it all depends on how much voltage drop you can live with.
Click to expand...

3% voltage drop

Kitchen / bathrooms / Misc Lighting for golf course "snack shop"
 
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L

Loffgren

Senior Member
Location
CA
480sparky said:
That really doesn't help. We need numbers.
Click to expand...

Ok, so the county is moving a building from one location to another 10 miles away, i dont have real numbers, sorry. So my plan was to feed the 200amp panel with a 200 amp circuit.

ready for stone and stick throwing
 
S

SEO

Senior Member
Location
Michigan
What will the connected load be? (100a, 150a etc.) You will have to know before you can calculate your voltage drop.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Loffgren said:
i dont have real numbers, sorry. So my plan was to feed the 200amp panel with a 200 amp circuit.

ready for stone and stick throwing
Click to expand...

No stones or sticks but trying to figure voltage drop without the load is a tough one. :)

Here are some examples

300' one way, 240 volt single phase, no more than 3% drop

200 amp load - 400 kcmil AL or 250 kcmil CU

160 amp load - 300 kcmil AL or 4/0 CU

140 amp load - 250 kcmil AL or 3/0 CU

Take your pick.:)
 
L

Loffgren

Senior Member
Location
CA
re

re

Ok 1.191 Sq in. with 3 250Kcmil and 1 #4

2" PVC it is ( up to 1.2734 )

Felt I need to show at least I used your guys help...
 
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