Damaging breakers upon installation and other theories

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mark32

mark32

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Currently in NJ
A few months ago I installed a transfer panel for a portable generator. (To help visualize this arrangement, I put this panel next to the main panel in which I reused an existing 100a breaker that was feeding an existing sub panel elsewhere in the house) When I re-energized the new panel I heard a sizzling coming from the existing Siemens or BR 100a breaker. When I removed it it was easy to see it had been arcing. I stuck a small flat head screwdriver into the part that pushes onto the buss and it was very weak, it had no strength left to it. I replaced it later in the day but a few thoughts entered my mind as to what caused this failure in the first place.

First thought, I, and most everyone I know, terminate a majority of breakers (All push on breakers by the way) once they are in the panel. I think by torquing the termination I/we are putting some stress on the tang that conforms to the buss.

Second thought, This breaker had #2 cu terminated to it and being a rather stout conductor, it possibly put continuous stress on those tangs, especially when you consider this breaker had not a breaker on either side of it.

Any thoughts?
 
Mark,
I have the same thoughts. I always get concerned when I see breakers that don't sit flat and square in the panel. When landing larger conductors, usually above #6 I strip and terminate them on the breaker, pull the breaker out, tighten the lugs with the breaker in my hand to the desired torque, then Rick it back into place.
 
Pullnwire, looks like you and I are the only two to have such thoughts/concerns. I really thought more would have shared similar assumptions or at least had the described situation cross their minds.
 
I see this as potentially a bigger problem with Siemens, GE, BR, and other similarly designed breakers. I also feel those designs are cheaper priced for a reason.

I do not see this as a problem at all with bolt on breakers or even I-Line and should be less of a problem with QO and CH style breakers.
 
What do the manufacturer's installation instructions say?

I know of some that say to land the wire on the breaker then mount the breaker, while other types (from the same manufacturer) say to mount the breaker then land the wire.
 
Okay, now we're getting somewhere. Jim, I haven't seen such installation instructions. I just looked over at schneider's website for Square D info and saw nothing of the sort. Could you provide a link to such info regardless of manufacturer?
 
mark32 said:
Okay, now we're getting somewhere. Jim, I haven't seen such installation instructions. I just looked over at schneider's website for Square D info and saw nothing of the sort. Could you provide a link to such info regardless of manufacturer?
Click to expand...

Load Centers - Homeline and QO
http://static.schneider-electric.us...QO Single Phase Load Centers/40271-419-04.pdf

3. Install the wire terminal end of the circuit breaker to the mounting rail and push inward until the plug-on jaw fully engages the bus bar connector. Keep the bottom of the circuit breaker
case against the mounting rail.
4. Remove the wire insulation from the branch wire as required. Install the branch wire into the load terminal of the branch circuit breaker.
 
Thanks Jim, I was actually hoping it would say something more along the lines of what you stated first in your post #5, that being to land the wire first, then mount the breaker. According to the Square D instructions, it mirrors what most do anyway.
 
mark32 said:
Thanks Jim, I was actually hoping it would say something more along the lines of what you stated first in your post #5, that being to land the wire first, then mount the breaker. According to the Square D instructions, it mirrors what most do anyway.
Click to expand...

Oh, you wanted this instead:
http://static.schneider-electric.us...ircuit Interrupters-AFCI/HOM/48840-122-03.pdf

6. Connect load power (D) and load neutral (E). See Figure 1 or side of circuit breaker for torque value.
7. Install circuit breaker into panel and re-torque wire connectors.
 
Interesting Jim, I wonder if they are suggesting such a procedure because the terminals are harder to get to (Once mounted) on afci's. Hmmm. Thanks!
 
mark32 said:
Interesting Jim, I wonder if they are suggesting such a procedure because the terminals are harder to get to (Once mounted) on afci's. Hmmm. Thanks!
Click to expand...
Never read those instructions before, and they likely are packed with every AFCI breaker in the box:angel:. But knowing how difficult the neutral terminal is to terminate compared to the ungrounded terminal on this and other breakers when installed, it it probably more about access to the terminal. Besides we are talking about conductors that will be no larger than maybe 10AWG for this particular breaker. What about the larger, stiffer conductor sizes terminated on a breaker causing problems as suggested earlier in this thread?
 
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