# Subpanel



## McClary’s Electrical (Feb 21, 2009)

steveo5880 said:


> When is a main-breaker needed to be installed in a subpanel?


 
Welcome to the forum. If the subpanel is in the same structure, never.


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## steveo5880 (Jan 25, 2011)

Thanks. How about if the subpanel is in the office part about 50' away?


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## BBQ (Nov 16, 2010)

steveo5880 said:


> Thanks. How about if the subpanel is in the office part about 50' away?


As long as it is in the same building and supplied by a properly sized feeder.... no.


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## jwjrw (Jan 14, 2010)

steveo5880 said:


> Thanks. How about if the subpanel is in the office part about 50' away?




Not required. An unattached garage or separate structure needs it's own disconnecting means unless fed with a MWBC. A panel mounted in the same structure does not require one.


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## steveo5880 (Jan 25, 2011)

Thank you for the help.


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## McClary’s Electrical (Feb 21, 2009)

jwjrw said:


> Not required. An unattached garage or separate structure needs it's own disconnecting means unless fed with a MWBC. A panel mounted in the same structure does not require one.


 
Good point and keep in mind the disconnecting means can be up to six breakers.


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## jwjrw (Jan 14, 2010)

mcclary's electrical said:


> Good point and keep in mind the disconnecting means can be up to six breakers.



And a panel mounted on the outside of a structure fed from a panel inside also does not require a main.


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## Shorty Circuit (Jun 26, 2010)

steveo5880 said:


> When is a main-breaker needed to be installed in a subpanel?


When it is supplied by feed through lugs from the main panel and has a rating less than the main panel. It is therfore not adequately protected by the breaker that protects the main panel and there is no subfeeder breaker to protect it.


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## sparks134 (Jan 30, 2009)

jwjrw said:


> Not required. An unattached garage or separate structure needs it's own disconnecting means unless fed with a MWBC. A panel mounted in the same structure does not require one.


I thought a MWBC still needed a disconnect in a separate structure???


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## RePhase277 (Feb 5, 2008)

sparks134 said:


> I thought a MWBC still needed a disconnect in a separate structure???


A single branch circuit feeding a detached structure needs no disconnect. Like running a receptacle or light to your shed. A MWBC is still a single branch circuit.


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> A single branch circuit feeding a detached structure needs no disconnect. Like running a receptacle or light to your shed. A MWBC is still a single branch circuit.


I disagree. It doesn't need a rod but it needs a disconnect. 225.31. I generally use a dp switch


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## jwjrw (Jan 14, 2010)

sparks134 said:


> I thought a MWBC still needed a disconnect in a separate structure???



It does but it can be a double pole switch. Sorry!


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## Dennis Alwon (May 9, 2009)

jwjrw said:


> It does but it can be a double pole switch. Sorry!


That's what I do but you can also use 2 sp switches.


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## RePhase277 (Feb 5, 2008)

Dennis Alwon said:


> I disagree. It doesn't need a rod but it needs a disconnect. 225.31. I generally use a dp switch


And a light switch in your shed would serve that purpose, as per the exception to 225.36.

Also note that a feeder _disconnect_ to an outbuilding in a single family dwelling needs to be 100 A, not 60.


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> And a light switch in your shed would serve that purpose, as per the exception to 225.36.


 That is true but a light switch is a disconnect.



> Also note that a feeder to an outbuilding in a single family dwelling needs to be 100 A, not 60.


 I disagree with both -- the feeder does not need to be 100 amp or 60.


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## RePhase277 (Feb 5, 2008)

Dennis Alwon said:


> That is true but a light switch is a disconnect.
> 
> I disagree with both -- the feeder does not need to be 100 amp or 60.


There should be a "disconnect" in there!:laughing:


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## sparks134 (Jan 30, 2009)

jwjrw said:


> It does but it can be a double pole switch. Sorry!


I thought that's what you meant


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> There should be a "disconnect" in there!:laughing:


That's better :thumbup:- but I still disagree with the 100 amps for a outbuilding in a resi. situation. Of course, if the outbuilding is a dwelling then you are correct.


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## RePhase277 (Feb 5, 2008)

Dennis Alwon said:


> That's better :thumbup:- but I still disagree with the 100 amps for a outbuilding in a resi. situation. Of course, if the outbuilding is a dwelling then you are correct.


Yeah, that was me quickly mis-reading the code. I saw that at a glance and said "hmmm... been wrong all these years." Now, upon a closer reading, it's still just 60A:laughing:


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## BBQ (Nov 16, 2010)

InPhase277 said:


> A single branch circuit feeding a detached structure needs no disconnect. Like running a receptacle or light to your shed. A MWBC is still a single branch circuit.





Dennis Alwon said:


> I disagree. It doesn't need a rod but it needs a disconnect. 225.31. I generally use a dp switch





InPhase277 said:


> And a light switch in your shed would serve that purpose, as per the exception to 225.36.
> 
> Also note that a feeder _disconnect_ to an outbuilding in a single family dwelling needs to be 100 A, not 60.





Dennis Alwon said:


> That is true but a light switch is a disconnect.
> 
> I disagree with both -- the feeder does not need to be 100 amp or 60.





Dennis Alwon said:


> That's better :thumbup:- but I still disagree with the 100 amps for a outbuilding in a resi. situation. Of course, if the outbuilding is a dwelling then you are correct.





InPhase277 said:


> Yeah, that was me quickly mis-reading the code. I saw that at a glance and said "hmmm... been wrong all these years." Now, upon a closer reading, it's still just 60A:laughing:



FWIW here is how I see it. 

*Grounding electrode* 

Required for feeders, not for single branch circuits and as noted a MWBC is a single circuit (See Article 100 definition)

*Disconnecting means*

All separate structures and buildings require one unless permitted by the exceptions.

Yes in some case a simple light switch could be the disconnecting means but it still has to meet the other requirements.



> The disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors. (See 225.32 )





> Two or three single-pole switches or breakers capable of individual operation shall be permitted on multiwire circuits, one pole for each ungrounded conductor, as one multipole disconnect, provided they are equipped with identified handle ties or a master handle to disconnect all ungrounded conductors with no more than six operations of the hand. See 225.33(B) )





> The two to six disconnects as permitted in 225.33 shall be grouped. (See 225.34(A) )





> Each disconnect shall be marked to indicate the load served. (See 225.34(A) )





> The building or structure disconnecting means shall plainly indicate whether it is in the open or closed position. (See 225.38(D) )


That one rules out Decora switches.


*Feeder size*

The feeder size only has to meet the size requirements of Article 220. It is not required to be 30, 60 or 100 amps.

The disconnecting means required by 225.31 must be rated in accordance with 225.39.


If a the calculated load shows you need 25 amps on each leg of the feeder you could install a 2 pole 30 amp breaker at the main panel, run 10/3 to the garage into a 60 amp main breaker panel.


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## Cletis (Aug 20, 2010)

*Main*

Here's how i look at it. What's the price difference of a 60 amp load center v.s. a 60 amp main breaker? $15-$20 bucks if that

Was it worth spending all your time investigating that for $15? 

Just get a main and be done with it and move on. 

Sorry, this is pet peeve of mine. People that try to spend all this time saving peanuts like personal time doesn't mean anything. You just lowered your profit but screwing around and trying to be a cheap azk. 

Now, if it was a 1000 amp main v.s. lug well....


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## jwjrw (Jan 14, 2010)

Cletis said:


> Here's how i look at it. What's the price difference of a 60 amp load center v.s. a 60 amp main breaker? $15-$20 bucks if that
> 
> Was it worth spending all your time investigating that for $15?
> 
> ...




Buy a main lug, back feed a 60 amp breaker, include tie down and you still have spent less than 50.00


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## Cletis (Aug 20, 2010)

*Ditto*

Ditto above

Start with this $40 out the door!!! 

http://www.castlewholesalers.com/SIEMENS-E0816ML1125S-125-Amp-Indoor-Main-Lug-Load-Center.html


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## Shockdoc (Mar 4, 2010)

Or just put in a six circuit panel.


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## RePhase277 (Feb 5, 2008)

Shockdoc said:


> Or just put in a six circuit panel.


That was killed in the '08 Code, but it was never a good idea in my opinion anyway.


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## Shockdoc (Mar 4, 2010)

InPhase277 said:


> That was killed in the '08 Code, but it was never a good idea in my opinion anyway.


I should stop living the past:jester:


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> That was killed in the '08 Code, but it was never a good idea in my opinion anyway.


What was killed in '08? You can still use a 6 cir panel with no main.


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## RePhase277 (Feb 5, 2008)

Dennis Alwon said:


> What was killed in '08? You can still use a 6 cir panel with no main.


I don't have an '08 book handy, so I'll use my '05 and try to remember the changes.

Under the '05 and before, the 6-circuit rule applied to panels that are listed as Service Equipment and are NOT lighting and appliance branch circuit panelboards. If more than 10% of the loads served are 30 A or less and have a neutral, then it is a L&ABCPB, and therefore not suitable for use as service equipment. A L&ABCPB needs protection on the line side.

I believe the '08 dropped the distinction between L&ABCPB and Power Panelboards. Hence, unless you have less than 10% of your circuits supplying loads with a neutral, the 6-disconnect rule won't apply.


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## Dennis Alwon (May 9, 2009)

InPhase277 said:


> I believe the '08 dropped the distinction between L&ABCPB and Power Panelboards. Hence, unless you have less than 10% of your circuits supplying loads with a neutral, the 6-disconnect rule won't apply.


True, the '08 dropped the L&ABCP but the 10% rule was also dropped. You can have 6 sp breakers as a disco if you want.


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## nitro71 (Sep 17, 2009)

Cletis said:


> Here's how i look at it. What's the price difference of a 60 amp load center v.s. a 60 amp main breaker? $15-$20 bucks if that
> 
> Was it worth spending all your time investigating that for $15?


Not in that example but think bigger. Three phase panels... Now the amount of dollars you just saved by not needing a main just went up substantially. I wouldn't sneeze at saving $15 bucks either. Think if every time you put in a sub panel you save $15. All adds up.


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