Tied Double Main

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abrownpe

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Florida (Tampa area)
For a second time, I've found a main panel with a double main it, ie it has (2) 150A Double Pole circuit breakers as a main with a tie between all 4 handles of the breaker. When is this done and why? Is it to code? This panel I don't have the right to open up and is in a business, the last one I knew was a no-no was in a residence. Anybody?
 
Do you have a photo? Is it like this?

97a5022a-462a-40c3-a96c-973263970615_400.jpg
 
abrownpe said:
For a second time, I've found a main panel with a double main it, ie it has (2) 150A Double Pole circuit breakers as a main with a tie between all 4 handles of the breaker. When is this done and why? Is it to code? This panel I don't have the right to open up and is in a business, the last one I knew was a no-no was in a residence. Anybody?
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There is nothing wrong with it, it is just how the manufacturer chose to make the breaker.

My own home has a 'four pole' 200 amp main.
 
The NEC does not let you freely "roll your own" from two 2-pole breakers.
But the manufacturer has engineered and tested this combination, and it has, I am sure, an internal common trip mechanism .
External handle ties alone cannot do that.
 
K8MHZ said:
Wow.

Are those really individual 150 amp breakers, or are the handles labeled to reflect the assembly current?

If each breaker could handle 150 amps, then it would take 300 amps to cause a trip, as the current would be divided equally between breakers, would it not?
Click to expand...

The labeling is the total.

I would bet you have a pair of 75 amp breakers in parallel for each line.
 
abrownpe said:
When is this done and why? Is it to code?
Click to expand...
The Code has nothing to say about a breaker manufactured as you describe.

The "why" is a matter of the manufacturer's engineering / economics. It is not for us, in the installation / maintenance field to question how, only a Nationally Recognized Testing Laboratory signs off on the assembly.

FYI, several manufacturers have done this type of Main Breaker assembly, and they are not restricted to "only commercial" or "only residential" or "only industrial" use.
 
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