do you need a main breaker in an electrical panel?

Answer 1

Depends on your term "need". There are panels available without and certain interpretations of codes that would allow their use. In some countries it quite normal to have a main switch not main breaker because faults should be taken care of by circuit breakers and system design should ensure maximum loads are not too high.

However, the cost is small relative to cost of the complete system and it makes most sense to have it, especially since the "no main breaker" option in the US is nothing (no main switch)

Answer 2

Despite the claims made above about a main breaker being mandatory in all circumstances, in the U.S. this is not necessarily true.

The National Electric Code allows, under certain very restricted conditions, that a main breaker is not required. However, these restrictions are such that there is still adequate ability to detect and clear faults on circuits.

For the vast majority of electrical panels, a main breaker is required. The points made by other respondents are true, in that a main breaker makes it easier to maintain the feeder breakers in the panel, however, they are not the primary reason for having the main breaker.

The primary reason for having a main breaker is that the overcurrent protection devices (typically a fuse) upstream of the panel, perhaps on the primary side of the service transformer in residential installations, would not be able to provide adequately co-ordinated backup protection to the individual feeder breakers on the small circuits. A 100 amp circuit breaker can backup a 15 amp circuit breaker, but not the transformer primary fuse (on the medium voltage side of the transformer).

Answer 3

depends on what you mean by main breaker. yes, all distribution panels need to be able to switch off the in-coming power mains. this does not need to be a breaker in the sense that it has a trip at a specified load, it can be manually operated.

you didn't say if you were talking about existing mains service, or for new distribution panel. i would always suggest a panel with a main breaker, even for sub-distribution circuits. Replacement of an existing service box just to put in a breaker might not be necessary.

Answer 4

Yes, a main breaker is essential to deactivate the entire electrical panel when you want to repair / remove / install a single circuit breaker or to immediately pull power from the entire house or office with one step (if there were smoldering wires and you could smell something burning, but couldn't tell where it was coming from).

By the electrical code, you are required to have a main breaker. Most all modern circuit cabinets have one.

Answer 5

If it takes more than tripping 6 breakers to shut-off all service, a main breaker is required

Answer 6

depends upon what the electrical code is being used in your country. Canadian Electrical code says:
14-606 Panelboard Overcurrent Protection
(1) Except for panelboards where more than 90% of the overcurrent devices supply feeders or motor branch circuits,EVERY panelboard shall be protected on the supply side by overcurrent devices having a rating not greater than that of the panelboard.
(2) The overcurrent protection required by Subrule (1) shall be permitted to be in the primary of a transformer supplying the panelboard provided the rating of the panelboard is NOT LESS than 125% of the rated secondary current of the transformer and the primary overcurrent device is rated or set at NO MORE than 125% of the rated primary current of the transformer.

Answer 7

Yes, aside from manditory laws and common sense, you can not service a system, at least safely, without it. The need to have a main shut down is real important for fire safety also.