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  • Writer's pictureTodd Engle

Shut it all down, The Main disconnect

All electrical systems require a means of disconnection so that the service can be shut down quickly if any dangerous conditions exist. In this section, we will look at the types of disconnects, and the common problems that need to be reported.

The service equipment is the necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load-end of service conductors to a house, and intended to constitute the main disconnecting means for service. The disconnecting means for service should be located outside or inside the house as close as possible to the point of entrance of the service conductors. The service equipment must be identifiable and marked as a service disconnect. A common service size for a single-family house is 200 amps. And the main 200-amp breaker located at a main panelboard would be the main disconnect for the service.


It is required that the entire electrical supply to the home be able to be shut off with six or fewer moves of the hand. This can be in the form of one or more knife switches, one or more fuses or fuse blocks, and, most commonly and in more recently built homes, by throwing the breaker(s).

If the supply cannot be disconnected from one location in this manner, the home inspector should report that the system is in need of repairs or upgrade.

Types of Disconnect

As discussed, different systems are in common use today, depending on the age of the property:

  • knife switch: This is the oldest type of disconnecting means. We all remember the old horror movies where Dr. Frankenstein was shown energizing his creation. The switches he used were knife switches.

  • fuse blocks: Often called mains and range panels, the electrical supply is shut down by pulling the two fuse blocks from the panel.

  • breaker(s): This is the most common type of disconnect we encounter. Throwing one or more breakers shuts off the electrical power. In most cases, we see a single main breaker, but there are "split-bus" panels where the homeowner would need to trip several breakers to effect a total shut-down.

Thank you InterNachi

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