MLO Panel

[papa]

When is it ok to use a main lugs only panel and where would a main breaker panel be required.

 

[StephenSDH]

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

 

[Dennis Alwon]

When is it ok to use a main lugs only panel and where would a main breaker panel be required.

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?

 

[don_resqcapt19]

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.

 

[Red Wiggler]

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.

 

[jim dungar]

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.

These are called 'molded case switches'.