I've always been confused on whether I need a main breaker for a sub-panel.
Situation 1 - Residential main service with a feeder breaker feeding sub-panel mounted within or on home. Is there a situation when the sub-panel needs a main?
Situation 2 - Residential main service with a feeder breaker feeding sub-panel mounted on seperate structure or somewhere else on property. Sub-panel only needs a main IF there are more than six breaker handles (twin counts as two handles), correct?
Situation 3 - 400A residential main service with first 200A main supplying the built-in distribution. Second 200A main feeding 20/40 sub-panel located on other side of house. Sub-panel has conduit provisions to supply future sub-panels located on other structures or areas of property.
Situation 4 - Commercial main service on exterior of building. Individual feeder (main) breakers feeding sub-panels located in each commercial suite. Every sub-panel I've ever seen in these situations always has a main breaker.
[This message has been edited by royta (edited 02-14-2007).]