# Size of Sub-panel's main bkr.



## subelect (Nov 25, 2007)

I have a customer that just remodeled his porch to be used as his laundry. 
He is adamant that he wants a sub-panel with a main bkr in the porch so he can shut off all equipment if there are any issues. He told me three different times to make sure I installed a panel with a main. 
In addition to the washer and dryer circuits, I will have 3 other branch circuits (5 throws total). When I replace the service panel next week, I plan to run an 8/3 Romex out to the new sub-panel, fed from a double pole 50 amp bkr. in the service entrance. 
It is less expensive for me to purchase a 12 space panel with a 100 amp main than using an 8 space panel with a back-fed main bkr and hold down device. Plus, with the 12 space panel, the customer will have spaces remaining. 
Is it against Code to use that 100 amp main with 8/3 NM? The wire is protected in the service entrance, so my gut feeling is that it does not matter what size main bkr. I use. Is this correct or do I have to replace that main bkr. with a 50 amp main?
Thanks,
Rick


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## Dennis Alwon (May 9, 2009)

You can do that however you better check the ampacity of 8/3 nm. Remember it is rated 60C


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## Turtle3000 (Feb 25, 2012)

8/3 @ 60c is only good for 40 amps I believe


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## JHFWIC (Mar 22, 2012)

I would run 6/3.


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## MDShunk (Jan 7, 2007)

Since your subfeed is overcurrent protected at the breaker it leaves in your main panel, that "main breaker" in the new laundry room is nothing more than a local disconnect. It does nothing as far as overcurrent protection goes (under 99 out of 100 normal circumstances). You could put a 1200 amp main there, if you felt like it.


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## subelect (Nov 25, 2007)

Thanks for the advice, I appreciate it.
I have to make sure that the lugs on the sub-panel are rated for the size NM wire that I run to it. My favorite AHJ has pointed that out to me in the past that I put too small of wire into the lugs and bending the wire over (doubling it) is not legal.
My latest mistake that he graciously invited me to correct was to have more than one EGC (not neutral) under a lug at a time. I can't find anything on the panel nomenclature nor the NEC to say that you are allowed to double up ground wires. He prefers single EGCs and if you run out of room, pigtail to wire nuts. 
Anyway, thank you for your input. 
Rick


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## MDShunk (Jan 7, 2007)

subelect said:


> Thanks for the advice, I appreciate it.
> I have to make sure that the lugs on the sub-panel are rated for the size NM wire that I run to it. My favorite AHJ has pointed that out to me in the past that I put too small of wire into the lugs and bending the wire over (doubling it) is not legal.
> My latest mistake that he graciously invited me to correct was to have more than one EGC (not neutral) under a lug at a time. I can't find anything on the panel nomenclature nor the NEC to say that you are allowed to double up ground wires. He prefers single EGCs and if you run out of room, pigtail to wire nuts.
> Anyway, thank you for your input.
> Rick


You're allowed 2 egc's under the same screw in most panel brands. The little sticker that comes with the ground bar kit says one or two #14's or #12's.

One good way to get a small conductor in large lugs is to take the lug off, crimp a ring terminal on the end of the conductor, and use the lug attaching screw to bolt the ring terminal to the bus.


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## scrypps (Apr 3, 2011)

MDShunk said:


> You're allowed 2 egc's under the same screw in most panel brands. The little sticker that comes with the ground bar kit says one or two #14's or #12's. /quote]
> 
> That's not the case, its very important to look at that sticker. I'm friends with a member of code panel 3 and he is very adamant about this. There are very few bus bars that really allow more than one conductor per lug.


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## scrypps (Apr 3, 2011)

scrypps said:


> MDShunk said:
> 
> 
> > You're allowed 2 egc's under the same screw in most panel brands. The little sticker that comes with the ground bar kit says one or two #14's or #12's.
> ...


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## ohmega (Apr 19, 2010)

scrypps said:


> scrypps said:
> 
> 
> > That's not the case, its very important to look at that sticker. I'm friends with a member of code panel 3 and he is very adamant about this. There are very few bus bars that really allow more than one conductor per lug.
> ...


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## MDShunk (Jan 7, 2007)

scrypps said:


> scrypps said:
> 
> 
> > That's not the case, its very important to look at that sticker. I'm friends with a member of code panel 3 and he is very adamant about this. There are very few bus bars that really allow more than one conductor per lug.
> ...


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## scrypps (Apr 3, 2011)

Remember, if you are using type NMS cable (romex) you have to use 6 guage wire for 50 amps. 8 copper is good for the 75 degree column, so you can use it in pipe or some other wiring method thats rated for 75 degree. 

I just had an argument with someone about this, they are more senior, so I conceded, but 240.4 gives layouts for small conductor amperage, #8 doesn't fall into the requirments of 240.4.


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## scrypps (Apr 3, 2011)

My bad, you're right, that rule is for the grounded conductor not the egc. 408.4 says you can't land a neutral with another neutral, or a grounded with another grounded, in the same termination, unless the conductors are in parallel and the the terminal is identified for it.


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## BBQ (Nov 16, 2010)

MDShunk said:


> Since your subfeed is overcurrent protected at the breaker it leaves in your main panel, that "main breaker" in the new laundry room is nothing more than a local disconnect. It does nothing as far as overcurrent protection goes (under 99 out of 100 normal circumstances). You could put a 1200 amp main there, if you felt like it.


Exactly.


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## Pistol (Aug 16, 2012)

I have always used #8 romex on a 40A breaker, but I have put it on a 50A on occasion.


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## manchestersparky (Mar 25, 2007)

scrypps said:


> My bad, you're right, that rule is for the grounded conductor not the egc. 408.4 says you can't land a neutral with another neutral, or a grounded with another grounded, in the same termination, unless the conductors are in parallel and the the terminal is identified for it.


I believe the correct code section would be 408.41

408.41 Grounded Conductor Terminations. Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor

Exception: Grounded conductors of circuits with parallel
conductors shall be permitted to terminate in a single terminal
if the terminal is identified for connection of more
than one conductor.


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## Dennis Alwon (May 9, 2009)

Pistol said:


> I have always used #8 romex on a 40A breaker, but I have put it on a 50A on occasion.


That may be compliant for a/c units or motors but not ranges or panels


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