Maybe a dumb question

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tonype

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I recently read on a panel - "The sum of breaker ratings connected to any one stab is 140 amps". THis was an older Murray panel (ca. 1960's).

I am trying to figure out what this means and everything I can think of makes no sense. I am likely missing something very obvious.

Any insight?
 
In this case, a stab to me is the connection between the breaker and the bus bar. I'm not sure if they mean there's a limit of 140 amps per stab (connection), or to the bus bar (70 on each side).

The largest stab-in breaker I've ever seen is 125 amps.
 
My guess is that since two breakers opposite of each other will share the same piece of copper detail the total current that the piece of detail can safely handle is 140 amps.
 
Does not make sense but I think it means if you have more than 7 20 amp breakers plugged into the panel on one phase that would violate the listing. Is this a 150 amp panel?
 
Typically the panel will have vertical bus bars with horizontal bus on each phase. The horizontal pieces will have a much lower current rating than the vertical pieces therefore the manufacturer will limit the total current connected to any one horizontal stab. Two opposite breakers share the same stab. For example circuits 1 and 2.

I recently installed a distribution panel with 4-100 amp 3 pole CB's. The first was connected to 1,3,5 the second connected to 8,10,12, the third connected to 13,15,17 the fourth to 20,22,24. This limited the connection to any one horizontal bus stab to 100 amps.
 
Dennis Alwon said:
Does not make sense but I think it means if you have more than 7 20 amp breakers plugged into the panel on one phase that would violate the listing. Is this a 150 amp panel?
Click to expand...

It is a 200 amp panel *Model LC216EC) - you idea was the 1st I thought of, but with the number of breakers present, this did not add up
 
infinity said:
Typically the panel will have vertical bus bars with horizontal bus on each phase. The horizontal pieces will have a much lower current rating than the vertical pieces therefore the manufacturer will limit the total current connected to any one horizontal stab. Two opposite breakers share the same stab. For example circuits 1 and 2.

.
Click to expand...

I think I understand - makes sense.
 
infinity said:
My guess is that since two breakers opposite of each other will share the same piece of copper detail the total current that the piece of detail can safely handle is 140 amps.
Click to expand...


As it was explained to me years ago: GIVE THIS MAN A CUPIE DOLL!
 
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