What is the six breaker throw rule?
Monday, February 3, 2020
The “six breaker throw rule” is a requirement in the National Electrical Code [NEC 230.71(A)]) that a service must have have a main disconnect that shuts off all power and it cannot take more than six switch throws to do it. The main disconnect or disconnects also must be clearly marked, as in the photo above.
Most service panels today have a single main disconnect, but there was an era in the mid-20th century when a panel with multiple mains, called a “split-bus panel,” was often used for residential construction. For more details, go to our blog post What is a split bus electric panel?
Subpanels are not required to have a main disconnect, with one exception. See Does a subpanel require a main breaker by code? for more on that. Also, we suggest reading When was the "maximum of six switches or breakers" first required for the main disconnect in a house electrical system?
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