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Circuit breaker to distribution panel connection

Circuit breaker to distribution panel connection

Circuit breaker to distribution panel connection

(OP)
I've received a panel breaker from the sales-distributor. I've never see before a bus connection with this kind of sharp cut. Does this bus connection it's acceptable?
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RE: Circuit breaker to distribution panel connection

If that is the FACTORY connection that is part of the UL listed assembly from Sq. D, then yes, it's OK. If on the other hand someone MODIFIED a "MLO" or convertible panel by making their own "MBK" (main breaker kit) as this appears to be, then it is NOT OK. Assuming from the fact that these are Sq. D breakers that you are in North America, the NEC or CEC is not going to permit you to install this legally if it is going to be inspected. If it is not going to be inspected, you can do what you like at your own risk.

"Will work for (the memory of) salami"

RE: Circuit breaker to distribution panel connection

I should add, the sharp angle, at low voltage like this, is irrelevant. My concern is more that from the looks of it, they have used the standard mechanical compression lugs to clamp onto solid bus bars. If so, I seriously doubt that is a tested and approved procedure. The photo however does not provide enough detail on that issue to be absolutely sure though.

"Will work for (the memory of) salami"

RE: Circuit breaker to distribution panel connection

I don't like this. The rating looks like 50A. The selection of the conductors looks like it was based on the conductor size required to mount the single phase breakers. Breaker manufacturers will stipulate a minimum conductor size not for current carrying capacity but for its ability to thermally conduct heat away from the breaker. You may wish to check this out. The centre one looks like it is tinned. Why?

The single phase breakers are mounted below the main breaker. If the main breaker was to open under fault conditions, where would the flash go? Would the breakers below survive? Also you will see small circular holes at the base of the face with a slot facing down. These are for flash barriers that are not present. What is the fault level?

RE: Circuit breaker to distribution panel connection

The contacts and the flash are generally at the top of this style of breaker. The trip mechanism is at the bottom.
I would be concerned with heat transfer if a flat bar is clamped in a connector designed to clamp round conductors.
But it may be worth a call to the AHJ to see if this is acceptable or a call to the distributor asking for verification that this is a valid manufacturers build.
It may be that the panel, bus bars and jumpers are built to 100 Amp or even 200 Amp standards and there is ample thermal capacity to operate safely with a 50 Amp breaker.
Anecdote:
We needed a 200 Amp sub panel for a job. No 200 Amp panels would fit in the space available. We only needed two or three large breakers and a 100 Amp panel would fit in the space available and hold the breakers with space left over.
My boss went about trying to get the manufacturer to supply a set of 200 Amp bus bars for a 100 Amp panel. He got the run around for a week or so.
Finally he got high enough up the food chain to get an answer:
The senior customer service person explained that they used the same size bus bars for both 100 Amp and 200 Amp panels. It was the number of breaker spaces that dictated the Amp rating of the panel in their lineup.
Solution;
I am sending you a set of 200 Amp stickers to affix to the bus bars. I hope that helps you out. No charge.
The point is, the parts may be quite safe at 50 Amps.

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

RE: Circuit breaker to distribution panel connection

The MCCB looks like a variant of Merlin-Gerin's NS or NSX series, and they are definitely capable of accepting a flat bar connection with an Allen screw. The cable clamp entry is another option for that breaker. Is the buswork a 'special' because the new breaker is a retrofit to an old board, or is the contractor cutting costs by using non-OEM parts? Or is that actually an OEM part?

A bit of heatshrink sleeve in lieu of the interphase barriers doesn't cost much.

RE: Circuit breaker to distribution panel connection

The more I look at this, the more I think it is a kluge job. This is a single phase Square D panelboard, but that is a 3 phase breaker. Even though Schneider owns both MG and Sq. D, I don't think the Sq. D single phase panels would use an MG 3 pole breaker as a Main, there is no need to, Sq. D makes perfectly good 2 pole main breakers. In addition, I believe that MG breaker will need to have the power "looped through" all three poles, otherwise the trip sensing elements will be biased to act too soon, causing nuisance tripping. I find it hard to believe that Sq. D would make that kind of blunder from the factory.

More likely, someone had an MLO (Mail Lug Only) panelboard, then when you needed an MCB version, they could not get the retrofit kit fast enough and kluged this together with parts on hand. If I were an inspector, I would reject it.

"Will work for (the memory of) salami"

RE: Circuit breaker to distribution panel connection

I agree with Jeff that this looks like a field-designed masterpiece. It might last 50 years, but it is probably not per UL and thus an NEC violation.

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