When is a main breaker required in a distribution panel

[mull982]

Can anyone tell me what the requirements are for when a main breaker is required in a distribution panel? Is there a section in the code that covers this?

I know that if the panel is rated the same as an upstream breaker feeding the panel then no main is required. I also know that if a panel is sub fed with feed through lugs then no main is required if the sub-fed panel is the same rating as the main in the upstream panel. Is this correct?

The only case I can think of where a main is required is possibly a panel located on the secondary of a transformer in order to satisfy the requirements of the secondary protection of the transformer.

 

[charlie b]

Short answer: "Never."

Longer answer: Nothing ever requires a main breaker in any panel of any description. Nothing. Nada. Zilch.

There are rules that say that all conductors must be protected against overcurrent, and other similar rules about panels, and still other rules about transformer secondary windings. You have addressed them already. But even in those cases where a overcurrent protection is needed, you are never required to achieve that protection by use of a main breaker in a panel.

 

[Dennis Alwon]

If by distribution panel you mean main distribution panel then the only time you need a main breaker is when you have more than six handles. If this is a sub panel then the only time a main is required is again over six disconnects at a detached structure.

 

[augie47]

I would direct you to 408.36, 230.71 and 225.33

 

[readydave8]

550.11 seems relavent?

 

[jim dungar]

I would direct you to 408.36, 230.71 and 225.33

None of those require the main device to be located inside of the panel.

 

[Chamuit]

I had to put one in a panel to maintain the series rating of the system once.

Required by the engineer.

 

[jim dungar]

Required by the engineer.

The engineer's desires are not code.

I do know that UL's series rating do not require the upstream device to be in the same enclosure as the lower rated device.

 

[augie47]

None of those require the main device to be located inside of the panel.

Jim, I agree, I was simply trying to provide some references.

 

[Eng]

The engineer's desires are not code.

I do know that UL's series rating do not require the upstream device to be in the same enclosure as the lower rated device.

And the code is not a design manual. NEC 90.1

 

[norcal]

And the code is not a design manual. NEC 90.1

If that is the case, please explain the requirement for a neutral for switches in the 2011 NEC? A bit off topic but when that is brought up, it makes me wonder.

 

[kwired]

None of those require the main device to be located inside of the panel.

That is correct. Inside the panel is often the choice that makes the most sense but is not a requirement.

If that is the case, please explain the requirement for a neutral for switches in the 2011 NEC? A bit off topic but when that is brought up, it makes me wonder.

In recent years the NEC has gone against their own words and made it more of a design manual in many cases. Usually to protect the unqualified installers or service people that don't use the NEC anyway

 

[Eng]

If that is the case, please explain the requirement for a neutral for switches in the 2011 NEC? A bit off topic but when that is brought up, it makes me wonder.

Makes me wonder also. Seems like with this requirement the NEC is stepping into the design of systems and not necessarily sticking with creating an electrically safe installation.

The requirement for neutrals at switches should be up to the facilities maintenence and engineering staff if they would like the flexibility in the future to replace a switch with a peice of utilization equipment, an outlet.

 

[kwired]

Makes me wonder also. Seems like with this requirement the NEC is stepping into the design of systems and not necessarily sticking with creating an electrically safe installation.

The requirement for neutrals at switches should be up to the facilities maintenence and engineering staff if they would like the flexibility in the future to replace a switch with a peice of utilization equipment, an outlet.

That is not the reason the neutral is required. Proximity sensors, timers, and other automatic switching devices that may require a neutral to operate is the main reason for this rule. Note you do not have to have a neutral in the switch box if there is an easy way to get one there such as raceway wiring method with capacity to pull a neutral later if needed.

 

[jim dungar]

Just because it contains several requirements, still does not make it a design manual. It also contains some definitions, but I doubt you would call it a dictionary.

 

[iwire]

Just because it contains several requirements, still does not make it a design manual. It also contains some definitions, but I doubt you would call it a dictionary.

IMO once you start indicating where outlets must be installed it becomes a design manual.