600 amp service question

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contrax

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I have a set of plans that show a 600a disconnect outside at power company drop. 2 4inch pvc conduits running under slab and stubbed up in space approx. 100 ft away. Drawings show parallel 500 alum. feeders pulled in to a trough above a drop ceiling and tapped to a 400 a mb and a 200a mb panel boards with tapped conductors 250 alum to 200 and parallel 250s to 400. Do these tapped feeders to panel boards have to be a certain length? Thanks in advance for any response. I have never seen a service drawn like this before, is this a unordinary application?
 
contrax said:
I have a set of plans that show a 600a disconnect outside at power company drop. 2 4inch pvc conduits running under slab and stubbed up in space approx. 100 ft away. Drawings show parallel 500 alum. feeders pulled in to a trough above a drop ceiling and tapped to a 400 a mb and a 200a mb panel boards with tapped conductors 250 alum to 200 and parallel 250s to 400. Do these tapped feeders to panel boards have to be a certain length? Thanks in advance for any response. I have never seen a service drawn like this before, is this a unordinary application?
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"Unordinary" maybe, but is still code compliant as long as the tap rules Dennis mentioned are not violated.

A 600 amp panelboard may be easier and cost less than a 200 and a 400 plus everything needed to make those taps and the extra labor to assemble it all, and would be compliant also.
 
Thanks for the reference Dennis, I will plan on setting my trough within 25' of the 2 panels. I looked up the reference 240.21(B) and it will work since my service is fused at 600 my smallest tapped conductors at a 1/3 would be 250 alum. (200 amps). I agree also a 600a panel would be a lot less expensive but I have a lot of branch circuits coming into the top of the cans. I am actually thinking of using 1 can for the 400 and 2 cans for the 200, 30 circuits in each can. 200 amp main with feed thru lugs to second can MLO. I show 54 branch circuits in the 200 and only 12 in the 400. 400a can has all the A/C and Kitchen equipment. Thanks again, Great forum here.
 
contrax said:
Thanks for the reference Dennis, I will plan on setting my trough within 25' of the 2 panels. I looked up the reference 240.21(B) and it will work since my service is fused at 600 my smallest tapped conductors at a 1/3 would be 250 alum. (200 amps). I agree also a 600a panel would be a lot less expensive but I have a lot of branch circuits coming into the top of the cans. I am actually thinking of using 1 can for the 400 and 2 cans for the 200, 30 circuits in each can. 200 amp main with feed thru lugs to second can MLO. I show 54 branch circuits in the 200 and only 12 in the 400. 400a can has all the A/C and Kitchen equipment. Thanks again, Great forum here.
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Since they have removed the 42 circuit minimum you can get 84 circuit panels, maybe more but 84 is most I have seen and have installed a couple of them. They were all 400 amp panels, can't tell you what you will find with a 600 amp main. If you need more room in top of cabinet for raceway entries that is what aux gutters are for, and sounds like you were going to use some anyway for making feeder taps, but maybe they can be a little smaller if you don't have all those large feeder conductors in it.

Another option that is maybe easier or possibly cost less is a panel with a 600 amp main and 600 subfeed lugs, then feed a main lug panel right next to the main panel via the subfeed lugs - then you simply have feeder and no feeder taps, one main breaker and no additional larger more expensive breakers.
 
Update on Service

Update on Service

After reading your advice kwired I spoke with the EE on the project and my local supplier and installed a 600a MLO 54 circuit inside and set a 200a MCB feeding 200a MLO 42 circuit right beside it. This saved some money and was easier than the trough and taps. I did have to spend a day digging up the 4 inch conduits outside and rerouting them under the slab to panel locations, but was well worth it. Made a nicer looking job than running them up the back and popping inside above ceiling. Just wanted to take a minute with an update and say thanks for the advice.
 
The 600 amp MLO requires a disconnection means if it's a separate structure.

The 600 amp MLO requires a disconnection means if it's a separate structure.

Sorry, I didn't mention the 600a MCB at the meter center.
 
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