Wire size for a 480V 3PH / 1200 Amp Service
- Thread starter dsmith411
- Start date
- Status
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
When a service or load is referred to as xxx Amps, that is always per phase, whether it is single phase or 3 phase.
- Location
- Massachusetts
Each set of phase conductors will have to total at least 1,200 amps the NEC allows a smaller neutral in some cases.
For us a 1,200 amp feeder is often three sets of 600 kcmil copper.
So that is a total of 12 - 600 kcmil (3A, 3B, 3C, 3N) and 3 appropriate sized EGCs for a 1,200 amp breaker.
For us a 1,200 amp feeder is often three sets of 600 kcmil copper.
So that is a total of 12 - 600 kcmil (3A, 3B, 3C, 3N) and 3 appropriate sized EGCs for a 1,200 amp breaker.
MyCleveland
Senior Member
- Location
- Cleveland, Ohio
EGC's...sure that right.
N's are return path.
N's are return path.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
- Location
- New Jersey
- Occupation
- Journeyman Electrician
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Ah. Got it. Thanks.
kwired
Electron manager
- Location
- NE Nebraska
1200 amps per leg, as has already been mentioned. Also keep in mind requirements in 240.4(B) for over 800 amps - you can not use next size higher overcurrent protection so commonly seen use of 500 copper which has ampacity of 380 can be protected at 400, the next size device. But for over 800 amps you can't run three parallel sets of 500 as they only have a combined ampacity of 1140 amps.
Is copper busbar an option in this case?
I'm thinking you would probably need spreader bars in any case to land all the cables.
- Location
- Massachusetts
Likely it is but by a long margin a 1,200 amp circuit in my area will be done with muiltiple wire conductors of aluminum or copper. I even see circuits up to 4,000 amps run using wire.
Around here busway seems to start being looked at above 2,000 amps and often used when the electrical rooms are stacked so a vertical busway can be installed with multiple plug in tap provisions at each floor.
I really can't say why we don't use more of it. Maybe as simple as the way the pricing works out.
Busway uses less space but may cost more to purchase and install?
Most of the equipment we use has provisions for multiple conductors of appropriate NEC size for the ampacity of the equipment.
For instance, I would fully expect that a 1,200 amp panelboard will come equipped with terminals for at least four large conductors per phase and neutral.
A 3,000 amp switch might have ten terminals per phase.
kwired
Electron manager
- Location
- NE Nebraska
OP was landing on a 1200 amp main breaker in the panel, it likely had 3 or 4 port lugs that accept up to maybe 750kcmil conductors per port. But had it been a main lug only panel it still likely has similar 3 or 4 port lugs for main lugs.
I installed a 1200 amp service switch and fed a 1200 amp panelboard from that somewhat recently and supplied both with 4-500 kcmil aluminum conductors per line. They both had 4 port lugs like I described above.
I was thinking of within the panel rather than the supply to it.
For that we'd generally use SWA PVC or XPLE.
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