# 120v sub panel



## backstay (Feb 3, 2011)

When I do off grid stuff, it's mostly 120 volt. I will pull the main(branch circuit style) install a single pole instead. Then use a double pole to tie the buss together.


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## BBQ (Nov 16, 2010)

Slick, no doubled up terminals. :thumbup1:


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## HARRY304E (Sep 15, 2010)

BBQ said:


> Slick, no doubled up terminals. :thumbup1:


You're a Stiff..................:laughing:


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## frenchelectrican (Mar 15, 2007)

FlyingSparks said:


> Is there anything in the NEC that prohibits using a jumper to connect two bus bars together, to create a 120v sub panel?


I am pretty sure they did not mention too much on that part but I will suggest to make sure you make a warning note in front of the panel say " 120 volts only " so that way if someone try to find a way to get 240 volts they will find out it is not avaible so that one way you can do that.

Otherwise just do on one side of bussbar and skip the other breaker postion so that is the other option you can do but again use " 120 volt only " sign 

Merci,
Marc


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## Bugz11B (May 12, 2013)

Not sure if its allowed or not, I do think its a bad idea (I dont like the idea of potentially loading a phase and unbalancing my system). If you do go ahead and do it please follow Marc's advise and LABEL it clearly. I see your in Florida did FPL ask you to do it?? They have asked me to do it before.


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## chicken steve (Mar 22, 2011)

I'll come in on a 3rd for that notion, keep the multiwire branch circuits out of it and it'll probably be ok if it's not introducing too much of an unbalanced load to the overall system

~CS~


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## Bugz11B (May 12, 2013)

chicken steve said:


> I'll come in on a 3rd for that notion, keep the multiwire branch circuits out of it and it'll probably be ok if it's not introducing too much of an unbalanced load to the overall system
> 
> ~CS~


I think a multiwire would just be flat out illegal in this situation because it would be 2 circuits of the same phase sharing a neutral. That was the cause of the only burnout house I've seen caused by electric.
*edit* wasn't correcting you i was now 2nd'ing your comment


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## chicken steve (Mar 22, 2011)

a big 10-4 Erik

i'd like to think there'd be more than the usual 110.3B to tank this

there's an awful lot of them out there....

~CS~


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## BBQ (Nov 16, 2010)

HARRY304E said:


> You're a Stiff..................:laughing:


As usual a well thought out post by Harry. :laughing:


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## Speedskater (Oct 2, 2009)

_Middle Atlantic write about using a panel board as a 120/120 system:_

All same phase‟ 120/120 isolation transformer-based power distribution remains a recommended solution for any localized AV system (e.g. all equipment located in close proximity).
However, when it comes to a larger, or a more widely distributed AV system, the properties of a 120/240 split single phase arrangement are more beneficial.
There are two main reasons for this; the first is simply that *when it comes to 120/120 it is not always intuitive to think that the electrical panel board requires a double sized neutral bar.* If the panel is not factory-integrated into the isolation transformer there can be confusion in the field, leading to installation errors and, if indeed installed incorrectly, can introduce a dangerously undersized neutral bus into the facility.


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## FlyingSparks (Dec 10, 2012)

Just for everyone's notice, I haven't done this and I don't plan on doing this. I was merely interested after I saw there are small older panels out there that are 120v only. I had thought about whether or not converting a 120/240 into a 120 panel was nec-compliant. I do realize the downside of having to future-proof the installation, with a person that might not understand "120v only" and stick a dual-pole breaker in.


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## FlyingSparks (Dec 10, 2012)

Erik.Schaeffer said:


> Not sure if its allowed or not, I do think its a bad idea (I dont like the idea of potentially loading a phase and unbalancing my system). If you do go ahead and do it please follow Marc's advise and LABEL it clearly. I see your in Florida did FPL ask you to do it?? They have asked me to do it before.


Nah, I am in the progress energy, I mean duke energy controlled area. I am low voltage and this was something I was merely interested in, I do plan on trying to move up in the electrical industry and try to score a job as an electrical apprentice.


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## Big John (May 23, 2010)

I've heard of guys taking ungrounded subpanels in old houses, and converting them to straight 120V in order to get a ground conductor without repulling the feed (I think someone on here posted about doing that?). Seems like a good trick to keep your back pocket.


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## BBQ (Nov 16, 2010)

Speedskater said:


> _Middle Atlantic write about using a panel board as a 120/120 system:_
> 
> All same phase‟ 120/120 isolation transformer-based power distribution remains a recommended solution for any localized AV system (e.g. all equipment located in close proximity).
> However, when it comes to a larger, or a more widely distributed AV system, the properties of a 120/240 split single phase arrangement are more beneficial.
> There are two main reasons for this; the first is simply that *when it comes to 120/120 it is not always intuitive to think that the electrical panel board requires a double sized neutral bar.* If the panel is not factory-integrated into the isolation transformer there can be confusion in the field, leading to installation errors and, if indeed installed incorrectly, can introduce a dangerously undersized neutral bus into the facility.


There is no need for a larger neutral


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## Jlarson (Jun 28, 2009)

BBQ said:


> There is no need for a larger neutral


Consider the source, an AV outfit. They probably want a double size, solid brass, gold plated, cryogenic vapor treated neutral bar. :laughing: :laughing:


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## Speedskater (Oct 2, 2009)

Well the Neutral current will equal the sum of the A and B legs rather than the difference. Now, whether that requires a larger bus bar is a different question.

Some of the writers of the 63 page white paper are far from audiophiles. 

Henry W. Ott
Neil Muncy
Bill Whitlock

and the references even more-so.
Jim Brown
Mike Holt
Warren H. Lewis
Ralph Morrison
Philip J. Simmons

Not an audiophile on either list.


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## Big John (May 23, 2010)

For the install to be compliant the neutral conductor has to be at least the same ampacity as the feeder. That takes care of any concerns about multiple buses: You will not have more current leaving than you have coming in.


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## SteveBayshore (Apr 7, 2013)

We design 120 volt panels in the process plants that we build for control and instrumentation circuits. Usually a 3 or 5 kva 480x120/240 transformer with the secondary windings in parallel for a 120 volt only output. Install a jumper across the two main lugs and backfeed a single pole 50 for a main.
Eliminates the possibility of having 240 volts present in instrumentation or control enclosures that contain multiple circuits. Square D has built these for us numerous times in custom MCCs.


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## CFL (Jan 28, 2009)

I've installed 120v panels and 120v services for landscape lighting. Panel and meter can were 120/240v but I installed a jumper from bus to bus. All in the name of saving a buck.


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