NEC Panelboard Question

[VTer]

Hi All,

Let me start by stating that this is a NEC question. I have a situation with a 120/208V main switchboard with a 200A feeder CB that feeds a 200A MLO panel with feed-through lugs that further feeds another 200A MLO panel about 150 feet away. I would like to install sub-feed lugs in the first 200A MLO panel and branch off to feed another 200A MLO panel that would be another 150 feet away in the opposite direction. My understating is that since the feeder is rated for 200A on all three panels, this would not fall under the tap rule and can be done? Is this correct interpretation of NEC? Outside of loading limitations, are there any NEC restrictions of how many MLO panels can be feed-subfed from a single supply circuit breaker?

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla

 

[waross]

Two issues.
1. The AHJ may require a 200 Amp splitter adjacent to the panel feeding two other panels. You may not be able to find approved sub feed lugs. If you can find acceptable sub feed lugs, great.
2. The total load must be calculated to be less than can be supplied by the source 200 Amp breaker.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VTer]

Hi Bill,

Thanks for the response!
1. I am not sure what is a splitter? Sub-feed lugs and feed through lugs on one panel are double according to the panel manufacturer.
2. The total load is less than the 200A.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla

 

[waross]

Splitter: An approved assembly of a junction box with two, three or four bus bars complete with lugs for incoming and multiple outgoing cables.

Note: The second picture shows two cables in one lug. This is probably a code violation. It is doubtful that those lugs are approved for two cables under one set screw.
It is possible but not likely.
Splitters are available in different sizes.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VTer]

Thanks again Bill. Are you aware of any NEC restrictions on the number of panels to be fed from the single feeder like this besides the loading consideration?

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla

 

[waross]

I work under the Canadian Code. There is a lot of harmony with the NEC on general provisions and approvals.
It will be better to wait and see if someone with more NEC exposure posts in.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jmbelectrical]

In the NEC world, there is no limitation on the quantity of panelboards that can be served via sub-feed or feed-thru lugs. As long as conductor ampacity is maintained consistently throughout, there are no tap conductors and the tap conductor rules of the NEC do not apply.

As Bill already pointed out, you may run into an issue finding lugs that are suitable for accommodating conductors that would allow you to serve two panelboards from one. Typically, we would use sub-feed or feed-thru lugs to connect panelboards in a daisy-chain configuration.

I should mention that you may want to run this by your local AHJ, as well. A colleague of mine recently informed me of an incident in which an AHJ prohibited the use of feed-thru/sub-feed lugs entirely. I believe his objections primarily stemmed from the (what he perceived to be) long distance between panelboards. Oddly, the AHJ did not cite an NEC section to justify his objections, nor did anyone ask him for one.

 

[VTer]

Thank you all for your replies! I will discuss it further with the AHJ.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla