Feed Through Panel Question

[kraftymike]

I have a 400 amp main breaker that protects two feed through (400 amp bus rated ea.) panels A and A1 that sit side by side.

My question is:

Would it be permissible by code to run 400 amps parallel to these panels in the form of two pipes each containing a single set of 250 kcmil cu. "Pipe 1" feeds panel A and "Pipe 2" feeds panel A1 with a set of 250 kcmil jumpering the two panels together. Essentially creating a loop.


I don't believe I have ever seen this and I am guessing there must be a reason.

 

[Smart $]

Welcome, kraftymike!!!

My understanding of your description is a bit light of making sense, so let's clarify first. As I understand it, you have two MLO (main lug only) panels setting side by side, each also with feedthrough lugs. A 400A breaker remote to both panels supplies power to them. You want to run a conduit to each panel containing a set of 250kcmil conductors. Then you want to connect a set of 250kcmil jumpers from the feedthrough lugs of Panel A to Panel A1. Is this correct?

Are each of the panels rated 400A? ..or 200A each?

What I'm trying to decide is whether you have one parallel feeder or two feeder taps. I'm currently leaning towards taps, for which we need to know the distance (conductor length) from breaker to each panel...?

 

[augie47]

Interesting question.
My initial reaction was "no", but then I noted the wording in 310.4 states "electrically joined at both ends", not physically joined.
If both panels have 400 amp buss and the "tie" between" them is 400 amp, I would think the install was legal... unorthodox, but legal. Note that is one man's opinion.

 

[masterinbama]

Interesting question.
My initial reaction was "no", but then I noted the wording in 310.4 states "electrically joined at both ends", not physically joined.
If both panels have 400 amp buss and the "tie" between" them is 400 amp, I would think the install was legal... unorthodox, but legal. Note that is one man's opinion.

You wouldn't have cables capable of carrying 400 amps supplying each section.

 

[augie47]

You wouldn't have cables capable of carrying 400 amps supplying each section.

Would you not ? Forget the breakers for a moment. One set of conductors ties to the end of a 400 amp buss, another set to the other end. Is this any different from tying sets at one end ?
In essence, you have a 400 amp buss but your lugs are 48" apart rather than side-by-side.

 

[masterinbama]

Would you not ? Forget the breakers for a moment. One set of conductors ties to the end of a 400 amp buss, another set to the other end. Is this any different from tying sets at one end ?
In essence, you have a 400 amp buss but your lugs are 48" apart rather than side-by-side.

Well I guess you would.

 

[Smart $]

Would you not ? Forget the breakers for a moment. One set of conductors ties to the end of a 400 amp buss, another set to the other end. Is this any different from tying sets at one end ?
In essence, you have a 400 amp buss but your lugs are 48" apart rather than side-by-side.

From what I gather, it's not one bus... it's two. We do not know yet whether each bus is rated for 400A. Additionally, the bus-to-bus connection definitely isn't rated 400A.

 

[iwire]

From what I gather, it's not one bus... it's two.

That is what I get out of it too.

We do not know yet whether each bus is rated for 400A.

We do if we read the first post.

Additionally, the bus-to-bus connection definitely isn't rated 400A.

Does it have to be?

I have been thinking on this one and I don't know what to think.

I think you and I have talked about 'electrically joined' in the past and found it problematic.

Thanks for the image, that is how I understand the OPs installation.

 

[jxofaltrds]

Great first question. Making my brain hurt!

 

[augie47]

If, as post 1 states, both buss are rated at 400 and IF the link is rated at 400 (I was not clear if he had one set of 250's of two) I don't see the violation.

 

[masterinbama]

If it's a 400 amp twin the bus to bus cabling would be capable of being rated for 400 amps.

 

[Smart $]

We do if we read the first post.

Doh! Nothing I can say to save face on that one! :lol:

Does it have to be?
...
I think you and I have talked about 'electrically joined' in the past and found it problematic.

It has to be with my current mode of thinking. If it is not, then we have different length of parallel conductors to any point on either bus, resulting in a violation. If the jumper(s) are rated 400A, then we could possibly (???) consider the two busses as one, and thus the parallel feeder conductors electrically joined... :huh:

 

[kwired]

From what I gather, it's not one bus... it's two. We do not know yet whether each bus is rated for 400A. Additionally, the bus-to-bus connection definitely isn't rated 400A.

I would definately say that is not a NEC recognized parallel feed, and don't think the way I envisioned it from the OP is either but may be closer to being acceptable. Here is what I was thinking from his description:

 

[iwire]

I would definately say that is not a NEC recognized parallel feed, and don't think the way I envisioned it from the OP is either but may be closer to being acceptable. Here is what I was thinking from his description:

IMO what you are showing is a double lugged panel not a feed through panel, but I bet what you show is more likely the case.

 

[Smart $]

I would definately say that is not a NEC recognized parallel feed, and don't think the way I envisioned it from the OP is either but may be closer to being acceptable. Here is what I was thinking from his description:

Why speculate...???

 

[iwire]

Why speculate...???

It's what we do here ........... are you new?

 

[jxofaltrds]

Not a EE so help me understand.

In the picture will the 200 AMP draw come from the conductor on the left or will it draw some current from the 'panel' on the right. If it draws from the right also then will the conductor on the right carry more of the load than the left conductor? See where I am tring to go?

 

[Smart $]

It's what we do here ........... are you new?

:rotflmao:

 

[iwire]

In the picture will the 200 AMP draw come from the conductor on the left or will it draw some current from the 'panel' on the right. If it draws from the right also then will the conductor on the right carry more of the load than the left conductor? See where I am tring to go?

View attachment 7193

I think you may have nailed it.

The conductors feeding either panel are not the same length therefore a violation.

 

[Smart $]

I think you may have nailed it.

The conductors feeding either panel are not the same length therefore a violation.

Hey now, I said that back in post #12... :?