djcrzysounds@yahoo.com
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- Scranton, Pa
Just checking... 800 Amp 3 Phase 120/208 Volt Service. Incoming conductors to be 4 parallel 4/0 feeds (4 wires each phase).
800 Amp 3 Phase Service
- Thread starter djcrzysounds@yahoo.com
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djcrzysounds@yahoo.com
Member
- Location
- Scranton, Pa
I was trying to get away with only 2 conduit runs. Sorry for not explaining... Also is it possible to run 2 sets of Service conductors in the same conduit.(As seen in a separate thread in NEC Section)
As long as you adjust the conductors ampacity per table 310.15(B)(2)(a)
Roger
djcrzysounds@yahoo.com
Member
- Location
- Scranton, Pa
Please check my math. Using XHHW-2 Copper Conductors.
4/0 @ 260Amps
x2(sets of conductors per Conduit) 520 Amps
/1.25 (For derating) = 416 Amps
x2 (For 2 sets Conduit) = 832Amps
- Location
- New Jersey
- Occupation
- Journeyman Electrician
djcrzysounds@yahoo.com
Member
- Location
- Scranton, Pa
Thanks Guys... when it doubt.. just post it..lol... now comes the fun part... how do I get 8 wires through a weatherhead? The only ones I can find have holes for 7 conductors.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What size conduit?
djcrzysounds@yahoo.com
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- Location
- Scranton, Pa
Not sure yet... might depend on the Weatherhead... could be from 3" RMC or PVC through 4"
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Maybe you can re-calculate your neutral load and use a single neutral conductor.
djcrzysounds@yahoo.com
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- Location
- Scranton, Pa
I thought even with 120/208V 3-phase you could not derate the neutral. So if for an 800amp service you would need one or more conductors that had an ampacity of 800Amps or more.
jrannis
Senior Member
- Location
- Fort Lauderdale/ Miami
I gotta say thats a new one for me. Eight wires in a weatherhead. Is it Delta by any chance? Maybe just one larger neutral?
- Location
- Illinois
- Occupation
- retired electrician
The grounded conductor only has to be as large as required by the load calculations and 220.61.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I'm curious, if you used that method could you ever add any single phase 120 volt loads to the service in the future?
if I might add
with the requirements of 250.24(C)
- Location
- Illinois
- Occupation
- retired electrician
No different than adding any loads to an existing service or feeder...you have to do a new load calculation.
- Location
- Illinois
- Occupation
- retired electrician
Thanks for adding that point, Gus. In some cases, those with small neutral loads, that section will require a larger grounded conductor than does the load calculation.
djcrzysounds@yahoo.com
Member
- Location
- Scranton, Pa
I come up with a Neutral (Unbalanced load) of approximately 280 Amps. So if I call it 400 Amps and run two 4/0s (One per run) it will keep me at 7 wires per run and should not be a problem with conductor ampacity. The majority of my loads is a 200Amp 3 Phase Heater and about a dozen 3 phase motors Most of which are 30FLA and 2-3 are 5.5 FLA and a little HVAC(not 3 phase). Does anyone see a problem with this?
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