Main Breaker Question

[GLENN THOMAS]

Hi folks, I just finished installing a 60 amp sub feed and wiring in my detached garage and had the inspection yesterday. The inspector said that if I have more than 6 throws in the panel I will need to install a main breaker. The inspector said he would pass me as long as I gave him my word that I would install a main breaker.

The panel I used is a Square D from the big orange BORG and is supposed to be convertible from a main lug to a main breaker. Home depot doesnt have main breakers and no one working there knows how to convert it. The electrical inspector told me I could just rearrange my existing breakers and install a 60 amp breaker along with the rest of them and use that as a main.

Has anyone ever heard of this before. Im assuming he meant to connect the 2 hots to a double pole breaker and then install the breaker like any other. It seems to me that a breaker installed in this manner would basically be in the circuit backwards. Could I have misunderstood him or is this something that is commonly done?

TIA

Glenn

[Brad Sperr]

Do you have the model number of the panel you're using? I thought that the 60A 6-8 space Square D panels they have at Home Depot were main lug only, but I could be wrong. It sounds like the inspector was suggesting you install a back fed breaker, which works just like you described. I think you're also required to install a retaining clip on back fed breakers, but the real electricians should be of more help.

[GLENN THOMAS]

Brad,

I dont have the model number with me as Im not home today but the box has 12 spaces in it. Ive done more research since posting and according to the Square D web site boxes with less than 12 spaces are main lug only. I also found some info from there site on back feeding and you are correct on having the breaker secured some how. Now that I know that the use of a breaker in this manner is called back feeding I have found a lot more info.
I appreciate your response.

GT

[Chuck Werts]

I think Brad is correct. Back feed the breaker and there should be a retaining clip available.

[Bryan Wellman]

This is what you're looking for....

http://static.schneider-electric.us/...272-304-02.pdf

All you are doing is locking the breaker into the panel. This assures that it can't become loose and cause arching issues inside the panel.

[Aaron Wingert]

Agreed, if you're using a main lug only panel then you're best bet is to backfeed a breaker as a "main". The ampacity of the breaker should be equal to greater ampacity than the breaker in your main panel that feeds the sub. If you're feeding with 60 amps, there's nothing wrong with backfeeding a 100 amp breaker in the subpanel as there isn't more than 60 amps of potential in the subpanel (originating at your main panel's 60 amp feeder breaker).

From the NEC...
408.16 Overcurrent Protection:
(F) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type-main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.

The breaker must be retained in place as suggested. Since it is hot as long as it is connected to the hot feeder, the retention device is required to prevent it from being rolled off the buss bar by someone who doesn't know what they're doing.

Here's square D's option for Homeline and QO main lug panels..
http://ecatalog.squared.com/pubs/Cir...1100HO9902.pdf

[Brad Sperr]

Sorry I misread your post, Glenn, but I thought you might have one of the smaller Square D panels. Your right that the 12 space panel should have convertible mains. If it's a QO panel, then the breaker will be a QOM1 size. The model number will be QOMxVH (where x equals the ampacity you want). To install it you just remove the nuts holding down the main lugs and slip the bolt in main breaker over those studs and reinstall the nuts. Using a main, as opposed to a back-fed breaker, will save you a couple of spaces in your panel, and you can probably find one pretty cheap on ebay.

[Roger Frazee]

You have been given very good advice on the backfed main breaker and hold down kit required.

Just to add some information that only the diehards will want to read........

Your inspector is correct about a single throw service rated disconnect for the building but the 6 disconnect rule was never in the picture for your application.

Your garage requires a 'service rated' disconnect nearest the point of entrance' of the supply feeder. In order for that to take place using a load center panel it must be rated 'Usable for use as service equipment'. So to determine if it is look at the specifications sheet for the panel. Its located either on the door cover or a side wall of the enclosure.

It will look like the attached drawing at the end of this post.

The panel specs. must say that the backfed double pole breaker makes the panel suitable for service equipment... some panels do not have the provision for a back fed main breaker with hold down kit.

Prior to the 2008 NEC some inspectors are not aware that the 6 disconnect rule only applies if the panel is not used as an appliance and lighting branch circuit panel board. You can see this language in the below attached drawing. So if you have one circuit breaker 30 amps or less with a neutral connection in the branch circuit that supplies lights or an appliance you cannot use the 6 disconnect rule at all. This effectively eliminates the 6 disconnect rule as a means of service disconnect to a building in just about all residential load centers used as sub-panels to the dwelling service equipment where the first means of service disconnect is located.. In simple terms a single throw back fed breaker or single throw main breaker is required if the panel qualified as a LA&BCP.

Now this was all prior to the 2008 code cycle. In 2008 they elimated this LA&BCP thing all together and a qualifying single throw breaker is required as the building disconnect in these situations where you are sub-feeding a detached building load center.

One last thing that also disqualifies the panel if you could use the 6 disconnect rule is there must be at least one combination for a single phase panel using double pole or single pole breakers where 6 disconnects use up all of the spaces of the panel. An example would be if I have a 12 space panel and I install 6 double pole breakers in it ...that combination of breakers uses all the spaces of the panel. This is disregarding any split bus configurations which are no longer allowed. If you cannot fill all the spaces in the panel with some combination where 6 single throws of the hand disconnects all power to the building with all spaces occupied then the 6 disconnect rule cannot be used. This means if I have a panel in a detached residential building/shop with 12 spaces and by some miracle I am not using it as a LA&BCP then I could put a maximum of 6 single pole breakers in it but none of which could supply lights or receptacles at 30 amps or less using a neutral if my jurisdiction is on 2005 or prior. If 2008 then you must have a single throw breaker in that panel for the detached building disconnect if the breaker panel is where you want the building disconnect to be located. You could keep the mlo panel and install a remote single enclosure service rated disconnect which would serve as the building disconnect. Notice I'm saying disconnect there is no requirement that the service rated disconnect be a circuit breaker since the feeder is protected at the dwelling panel with a circuit breaker.

In these situations I prefer to use the mlo panel and install a single throw service rated disconnect upstream of the mlo panel at the point of entrance of the feeder either inside or outside the detached building. This does two things it meets the requirement for the "disconnect" to be located at the nearest point of entrance of the feeder to the detached building and then I can install the breaker panel anywhere I what inside if the nearest point of entrance is not suitable for my needs otherwise.

Now all that said the easiest way generally to satisfy code for the building disconnect is to install a single throw backfed double pole breaker or main breaker in the panel as long as the breaker panel containing the 'service rated' disconnect is located at the nearest point of entrance of the supply feeder.

Don't you just love how clear the NEC is....

[GLENN THOMAS]

Thanks everyone for taking the time to help out. I guess the big borgs dont sell the main breakers and out of the 2 Home Depots and 2 Lowes I couldnt find anyone with enough knowledge to know what I was trying to do. When I bought the convertible panel I just assumed HD would have the main breakers to convert it. In any case I went ahead and installed a back feed breaker and all is well.

Again, thanks for the help.

GT