MLO Panel

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Say you have a 800A panel with a 200A branch breaker that feeds a smaller 200 A panel the same voltage. The 800A panel already has the 200A branch breaker to protect the 200A panel so you can install a MB or MLO panel. I like specing a MB panel so if you are standing at the 200A panel you have a local disconnect. In this situation you have (2) 200A breaker protecting the panel, which is fine, who knows which one will trip or both. If there is a transformer stepping down the voltage for a panel then you need to have overcurrent protection between the transformer and the secondary panel, which you could commonly use the MB in your panel as this overcurrent protection device.

-Steve
 
papa said:
When is it ok to use a main lugs only panel and where would a main breaker panel be required.
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Main breaker panels are usually at the service as the main disconnects. main lugs are generally used as sub panels fed from the main breaker panels.

Do you have a particular circumstance you are thinking about?
 
I am not aware of any place where the code requires that the panel have a main breaker, however there are rules requiring overcurrent protection for the panel and rules requiring a means of disconnect for buildings. Often the most cost effective way to comply with these rules is the use of a main breaker.
 
Breaker disconnecting means

Breaker disconnecting means

Don't they make a breaker that is rated for the appropriate amperage, but does not have thermal interupting capabilities? In other words it is just a disconnecting means for the panel. It is still being protected by the up-stream breaker.
 
Red Wiggler said:
Don't they make a breaker that is rated for the appropriate amperage, but does not have thermal interupting capabilities? In other words it is just a disconnecting means for the panel. It is still being protected by the up-stream breaker.
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These are called 'molded case switches'.
 
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