sizing conductors by their downstream breakers inside a power panel.

[Silvamp]

I did not accept several power panels (ranging from 40A to 300A) that a contractor installed on a new building - these panels haven't been detailed well enough on the system's design.

The reason I: instead of using bus bars rated the size of the main breaker for the panel, they used a mix of bars and jumper cables. The problem was that most the jumper cables were sized by the downstream circuit breaker that this jumper was feeding.

Example: 70A 3 pole breaker had a piece(+/-4 inches) of 100A bus bar and from this bar several jumper cables feeding individual breakers. If one of these jumpers would feed a 20A breaker, then the jumper would be only a 12 AWG. As this jumper was connected to a 70A breaker, I made him upgrade the jumper to at least a 4 AWG cable. The same happened in larger panels, like a 225A main that had 6 AWG jumpers connecting the 50A breaker, etc.

I made them replace all the jumpers with proper bus bars as much as possible, but given the lay out of the panel and also the fact that I had to deliver the building in a very short time, where bus bars wouldn't be possible to be installed I allowed them to use jumpers but they had to match the size of the breaker upstream from it.

The contractor did it, but now he is questioning my action. He is saying that the downstream breakers would limit the current on the jumpers and that what I made them remove was no code violation at all! He can be right, but how about the possibility of a short on the jumper wires between the main breaker and the one downstream???

Could you guys judge my action and let me know if this is or is not a NEC violation?

 

[bphgravity]

There are code allowed feeder taps as specified in Section 240.20(B), but I'm not sure what you mean by "jumper cables" and all this home made stuff?

 

[iwire]

I agree with Bryan, from the description they sound like they would be taps as allowed by 240.20(B).

However if I am not mistaken it sounds like you had the EC re-wire a factory assembled panel board?

If this is the case the NEC is irrelevant as the panels would have been listed as shipped and now they have been modified.

That is something I would have strongly protested.

At the least I think you owe the EC T&M for the work you requested.

 

[dlhoule]

Example: 70A 3 pole breaker had a piece(+/-4 inches) of 100A bus bar and from this bar several jumper cables feeding individual breakers. If one of these jumpers would feed a 20A breaker, then the jumper would be only a 12 AWG. As this jumper was connected to a 70A breaker, I made him upgrade the jumper to at least a 4 AWG cable. The same happened in larger panels, like a 225A main that had 6 AWG jumpers connecting the 50A breaker, etc.

I am curious about this: Most of the 20A breakers I have seen will not take a 4AWG. Do these panels come from the factory with a main and a short piece of bus? What brand of panels are these? Could you possibly post a picture?

 

[iwire]

I am curious about this: Most of the 20A breakers I have seen will not take a 4AWG.

I doubt we are talking about residential single pole 20s here.

A GE 20 amp TED breaker will take at least a 4 AWG and all the other companies make large frame breakers similar to the TED.

I believe these are available down to 15 amp.

 

[Silvamp]

I appreciate all of your inputs.

After seeing Section 240.20(B), I saw that may be 1/2 the feeder taps (what I called jumper wires) could have stayed as they were (the ones feeding an overcurrent device like I described)

But, on some other cases, these feeder taps were feeding a smaller bus that had something from 5 to 10 smaller breakers connected- without a main for that bus. In that situation, no overcurrent device was connected to the feeder tap other then the main breaker where the taps came from.

I will talk to them, let them know about this and apologise for the ones they didn't need to change. Had they sent me the layout of those panels as we had agreed at the begining of the job, this wouldn't have hapenned. Instead, they showed up with these panels that looked like home made stuff and I wasn't very happy with them overall any way. They saved big money with other items that I let go by, so I don't really owe them any thing on this one. And they learned the lesson, next time I bet they will bring me their design or at least lay out for approval first. If anything, we will have time to discuss about anything I may not like. Had they showed me something like Section 240.20 I would of course change my mind... but they didn't and only came to complain later on.

Thanks a lot and take care!

PS: the #4 cable fit in the 20A (they are not TEDs) breaker by means of a "needle type" crimp on connector. Overkill... but just 1 or 2 ft of cabling.

I'd be glad to send some pictures of the "before" and "after", but I don't know how on this forum.