Service Overcurrent Protection

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bphgravity

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Assume a 400A service consisting of 2 - 200A main circuit breaker panelboards. From the service point to the meter socket, parallel 2/0 AWG conductors are used for the ungrounded conductors. On the load side of the meter socket, single 3/0 AWG conductors are installed to each 200A panelboard. The total calculated load is 250A.

Does this arrangement meet all the requirements of the NEC - (230.90, 310.15)?

The paralleled 2/0 AWG conductors will not be loaded to greater than 250A and have a derated ampacity of 280A. This complies with Exception #3 to 230.90(A). However, the individual service entrance conductors to each 200A panelboard must comply with the 310.16 rating of 200A or 3/0 AWG...

(The occupancy is not a dwelling)
 
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I'm not sure I understand the situation. 310.16 applies to both the sets of wires you described. I agree that the Exception you cited allows the use of a set of two paralleled 2/0 conductors. I agree that running 3/0 to each panelboard will give you adequate ampacity. What I am missing is the nature of the problem. Sorry.
 
At first I wanted to say the 3/0 conductors are taps, and taps aren't allowed on service entrance conductors.

But on second thought, I'm not sure if the taps are on the owners side or utilities side of the service point.

Also, 230.40 only allows one service drop or lateral to supply one set of service entrance conductors. So exactly where does the service lateral end, and where do the service conductors start?
 
Bryan what is confusing is "from service point"........ Lateral or drop to meter (poco) and then service entrance to panels or from service to sub panels via feeders.
 
I am only looking for confirmation on the code sections for a future class discussion. The service is imaginary.

Service drop, owned by utility, supplies service conductors at overhead mast. Service consists of parallel 2/0 conductors, to meter line side. On load side 3/0 conductors run directly to 2 - 200A main disconnects. I believe 230.40 Exception #2 qualifies the two sets of service entrance conductors.

All I am trying to work up is a good example using 230.40 and the exceptions, 230.90 and its exceptions, 310.15 derating requirements, and use of 310.16 all in one problem...

Sorry for the confusion...
 
Based on the information given, I constitutes a 90.4 violation.
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bphgravity said:
All I am trying to work up is a good example using 230.40 and the exceptions, 230.90 and its exceptions, 310.15 derating requirements, and use of 310.16 all in one problem...
Click to expand...

You gonna go for the works, and include 250 in the mix?
 
I thought you had to comply with the very first paragraph of 230.2 to use 230.40 Exception 2. (I hope I'm wrong, that would make life much easier.)

"For the purpose of 230.40 , Exception No. 2 only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service."

Steve
 
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