Does Building Code require a Main Breaker on a sub panel?

[sambelcher]

Hello,

My garage has a sub panel with a 10-3 wire running back to the main panel in the house.

I'm going to add some outlets and light fixtures, and I will ge getting a building permit. So, the work will be inspected, and I'll have to correct some things that were not done properly by the previous owner. (7 of the 8 wires in the panel don't have clamps on the wire where it enters the breaker box, wires are not stapled to the studs, etc.)

My question is this: The panel in the garage does not have a "main" shut off. There are individual breakers for each circuit, but no switch to kill power to everything. Is a main breaker required for a sub-panel?

Thanks
Sam

 

[Grazz256]

Are you in the US or Canada?

I don't think the CEC directly requires it, but its definately a good idea. Much easier to garuntee you won't get zapped if you can see where it was turned off.

 

[Gooch]

Hello,

My garage has a sub panel with a 10-3 wire running back to the main panel in the house.

I'm going to add some outlets and light fixtures, and I will ge getting a building permit. So, the work will be inspected, and I'll have to correct some things that were not done properly by the previous owner. (7 of the 8 wires in the panel don't have clamps on the wire where it enters the breaker box, wires are not stapled to the studs, etc.)

My question is this: The panel in the garage does not have a "main" shut off. There are individual breakers for each circuit, but no switch to kill power to everything. Is a main breaker required for a sub-panel?

Thanks
Sam

Attached or detached garage?

 

[StaggeringGoat]

It shouldn't need a main if there is already one at the main panel. You should have a "master" breaker in the main panel for this subpanel.

 

[Aceman]

It shouldn't need a main if there is already one at the main panel. You should have a "master" breaker in the main panel for this subpanel.

You can't say that for sure without him answering Gooch's question first:

Attached or detached garage?

 

[jake26]

What is 10/3 wire? 30 or 40 amps?

Just curious.

 

[theoldwizard1]

I am NOT a pro, but I was always told any remote panel requires a "disconnect" so you can do work on it "cold" without having to find the main and "lock it out" there. That does NOT necessarily mean a breaker.

I worked in "old" computer rooms for many years. Huge old A/C units. A few years ago, each was fitted with an external lock out/safety switch (even though most had internal ones).

 

[Salem747]

You don't NEED a breaker in a sub-panel, in Canada anyway. But it sure is handy if you ever want to do any work in the garage panel. You don't have to go to the panel in the house to shut off thepower to the panel.

Breakers aren't as pricey as they were for a while either. A 60A breaker is only $23. You do need a panel that has a spot for a main though. I ended up using a 100A panel for my garage that came with a 100A main but the service from the house was only 60A. So the 100A just acts as a disconnect.

 

[sambelcher]

The 10-3 is on a 30 amp breaker (in the main panel in the house.)

I'm in the USA - Seattle area.

And the garage is attached.

 

[Charles (in GA)]

The 10-3 is on a 30 amp breaker (in the main panel in the house.)

I'm in the USA - Seattle area.

And the garage is attached.

On a sub in a ATTACHED garage, no, no disconnect needed.

If it were detached, yes, it would need a disconnect (not a breaker per se, but it could be a breaker), either in or near the sub panel or outside the building where the feeder enters the building...... and the disconnect must be rated at no less than 60 amps (NEC225.39) if the feeder supplies or has the potential of supplying more than two circuits (even it the feeder is rated at less than 60 amp.)

Charles

 

[sambelcher]

Thanks to all for your replies. Now I just have to wait and see what kind of inspector I get.

 

[ddawg16]

It was my understanding that as long as the sub had 6 or less breakers, no main breaker in the panel was necessary. If more than 6, then the sub panel must have a main disconnect breaker in the panel.

 

[Gooch]

It was my understanding that as long as the sub had 6 or less breakers, no main breaker in the panel was necessary. If more than 6, then the sub panel must have a main disconnect breaker in the panel.

pretty sure that only applies to services, not sub feeders.

 

[AussieDan]

The relevant code sections are:

VI. Service Equipment — Disconnecting Means
230.70 General. Means shall be provided to disconnect all conductors in a building or other structure from the service entrance conductors.

II. More Than One Building or Other Structure
225.30 Number of Supplies. Where more than one building or other structure is on the same property and under single management, each additional building or other structure that is served by a branch circuit or feeder on the load side of the service disconnecting means shall be supplied
by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
225.31 Disconnecting Means. Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.

A subpanel in an attached garage is still part of the same structure, and is covered by the main breaker in the main panel. A detached garage is a separate structure, so it needs its own disconnect.

230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard.

225.33 Maximum Number of Disconnects.
(A) General. The disconnecting means for each supply permitted by 225.30 shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switch-board. There shall be no more than six disconnects per supply grouped in any one location.

Up to 6 breakers in a detached garage can be used without a main breaker in the subpanel, since you can shut off power to the structure using 6 or less breakers. Once you add a 7th breaker you would need a separate means to disconnect power to the structure, meaning the subpanel needs a main breaker or a back-fed breaker marked appropriately.

So, in an attached garage the OP is fine without a main breaker in the subpanel.

 

[BigJohn20]

Up to 6 breakers in a detached garage can be used without a main breaker in the subpanel, since you can shut off power to the structure using 6 or less breakers. Once you add a 7th breaker you would need a separate means to disconnect power to the structure, meaning the subpanel needs a main breaker or a back-fed breaker marked appropriately.

AussieDan,

There is a very relevant part in the NEC2008 that all but excludes standard 6 space main lug panels w/o a main breaker in detached buildings as the sole disconnecting means:

225.36 Suitable for Service Equipment.
The disconnecting means specified in 225.31 shall be suitable for use as service equipment.

Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.

 

[sambelcher]

Thanks very much. This is exactly what I needed to know.

If you have computer questions, I may be able to return the favor.

 

[AussieDan]

sambelcher,

Glad we could help!

BigJohn20,

I'm not sure that I follow how that would exclude a 6 space main lug panel, as it seems to fall within the definition of service equipment:

Service Equipment. 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 building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.

Am I missing something here?

 

[BigJohn20]

sambelcher,

Glad we could help!

BigJohn20,

I'm not sure that I follow how that would exclude a 6 space main lug panel, as it seems to fall within the definition of service equipment:

Am I missing something here?

A few of the MLOs I've seen are only rated as service equipment when used in conjunction with a main breaker/main breaker retention kit. It doesn't matter if it seems to fall in the definition of service equipment; the spec sheet on the inside of the panel has to say that it is rated for it.

I'll have to double check the 6 space Murray and Eaton MLOs, as we typically run a 10/20 or a main breaker renovation panel.

 

[AussieDan]

Seems like there is always another section waiting to trip you up! You are of course correct that the panel must be marked as being suitable for use as service equipment:

230.66 Marking. Service equipment rated at 600 volts or less shall be marked to identify it as being suitable for use as service equipment. Individual meter socket enclosures shall not be considered service equipment.

It seems like most main lug panels are only listed for use as service equipment with a separate disconnect or a back-fed breaker and clip. In any case (especially considering the small price differential between a main lug and main breaker panel) it makes sense to have a single disconnect that allows you to cut power to the garage in an emergency.

 

[v7guy]

I don't have a disconnect in the garage subpanel, but I do have a 100A breaker in the house main that feeds it. It's labeled "garage subpanel" and throwing it shuts off everything but the lights. NY is pretty **** and this was wired by a registered electrician, so I assume it's on the up and up.