Service/Feeders

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augie47

augie47

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Tennessee
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State Electrical Inspector (Retired)
Re-approaching a situation that had been discussed earlier but one on which I have now confused myself.
Single family residence, 120/240 volt 3 wire service.
Per 310.15(B)(6) I'm using a 600 al to feed a 400 amp meter socket.
From the load side of the socket I'm using installing XHHW AL service conductors to feed two 200 amp feed thru panels being used as service disconnects. As these individual service condcutors are not carrying "all loads associated with the dwelling", I size them per 310.16. In this situation my computed load on each panel is less than 180 amps, so I use a 4/0 XHHW utilizing 240.4(B).
From my two outisde service panels I extend coanductors into the house to feed two interior panels. I elect to use AL SER cable.
What size SER cable would be required under the '08 Code ?
 
augie47 said:
Re-approaching a situation that had been discussed earlier but one on which I have now confused myself.
Single family residence, 120/240 volt 3 wire service.
Per 310.15(B)(6) I'm using a 600 al to feed a 400 amp meter socket.
From the load side of the socket I'm using installing XHHW AL service conductors to feed two 200 amp feed thru panels being used as service disconnects. As these individual service condcutors are not carrying "all loads associated with the dwelling", I size them per 310.16. In this situation my computed load on each panel is less than 180 amps, so I use a 4/0 XHHW utilizing 240.4(B).
From my two outisde service panels I extend coanductors into the house to feed two interior panels. I elect to use AL SER cable.
What size SER cable would be required under the '08 Code ?
Click to expand...

You would have to use the 60C column and T. 310.16
 
augie47 said:
what about 215.2(A)(3) ??
Click to expand...

Well we have been thru that before. I believe that 215.2(A)(3) is an oversight but perhaps a legitimate argument.

(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. Paragraph 310.15(B)(6) shall be permitted to be used for conductor size.
Click to expand...

If you read the last sentence it can be interpreted that both the feeders and service conductors can be sized by 310.15(B)(6)
 
Gus it may be a loophole in the NEC or it may be as intended but to me if they are saying 4/0 ser should be rated 150 amps and we are using it for 200 amps it just doesn't feel right. I know my opinion is just that-- my opinion.

I know it will not fly around here. A friend got hit on it and he ended up changing the breakers to 150 amps-- thus the service was a 300 amp instead of 400 amp. It was cheaper to do that then to remove 100 feet of SER cable.
 
Dennis Alwon said:
If you have 2 main panels then it is not the main power feeder--
Click to expand...

Dennis, That was my point also, 215.2(A)(3) the last sentence says it's ok to use

"paragraph" 310.15(B)(6) to size the conductors, not Table 310.15(B)(6). In the paragraph

it says to use the table , it must be a main power feeder, and in this case it is not.

Also, I was looking in the copper side when I said 4/0 was ok in this service, and of

course, that was a mistake on my part.
 
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