3 Phase Panel for Single Plase

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Old 08-30-11, 06:07 AM
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3 Phase Panel for Single Plase

Is it possible to use a 3 phase breaker box for single phase? Someone gave me a 30 circuit 3 phase square D panel box and I'd like to use it as a sub panel for for garage. Can I just activite two hots and run a jumper to the other one so they all work? Or is there another way to do it?
thanks,
joe
 
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Old 08-30-11, 09:05 AM
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No jumper, just use A and B, and don't install breakers in any of the C spaces. In other words every third slot will remain empty.
 
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Old 08-30-11, 08:55 PM
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Is it possible to use a 3 phase breaker box for single phase?
Is it possible? Yes. Will the inspector allow it? Doubtful. Is it a good idea? No
 
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Old 08-31-11, 08:11 AM
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Don't forget, all the knock outs must be plugged where the third phase breakers would normally go as well as unused breaker locations where you do have service. For $30 I wouldn't mess with it.
 
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Old 08-31-11, 07:44 PM
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You'll also be only able to use 20 spaces.
 
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Old 08-31-11, 09:56 PM
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Originally Posted by CasualJoe View Post
Is it possible? Yes. Will the inspector allow it? Doubtful. Is it a good idea? No
Code reference?

Originally Posted by Justin Smith View Post
You'll also be only able to use 20 spaces.
A garage subpanel isn't going to require more than that.
 
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Old 09-01-11, 07:33 AM
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Originally Posted by JerseyMatt View Post
Code reference?
How about (2011) 110.3(A)(1), 110.12. It might even be a violation of the UL listing as it is intended to be installed as a three phase panel.

Originally Posted by JerseyMatt View Post
A garage subpanel isn't going to require more than that.
And a single phase, 20 circuit, 20 space panel with 5 breakers is about $53.
 
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Old 09-01-11, 08:05 AM
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Originally Posted by Tolyn Ironhand View Post
How about (2011) 110.3(A)(1), 110.12. It might even be a violation of the UL listing as it is intended to be installed as a three phase panel.
One could argue that it is future planning for installation of a rotary phase converter and 3 equipment, no?



And a single phase, 20 circuit, 20 space panel with 5 breakers is about $53.
Last time I checked, $53 > Free..
 
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Old 09-01-11, 08:27 AM
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But Matt, he's talking a garage, where he will use maybe 5 circuits, max. Sometimes "free" ain't. Think of space confinements, too. Small box...neat. 3 phase box...big and obtrusive......but "free"!!
 
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Old 09-01-11, 10:54 AM
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Free crap is still crap.

One could argue that it is future planning for installation of a rotary phase converter and 3 equipment, no?
Not really since the feed is from the house, not a phase converter. I am also thinking of the next poor homeowner who thinks he has tons of room in the panel only to fine 1/3 of the spaces are dead.
 
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Old 09-01-11, 10:55 AM
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yeah true


...................
 
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Old 09-01-11, 11:59 AM
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Once ran into a commercial electrical upgrade where the contractor used a residential single phase panel to replace a three phase panel. When he got through the customer noticed the AC units weren't cooling. Guess why? LOL
 
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Old 09-01-11, 12:40 PM
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I wonder what he did with the C phase conductor -- left it dangling? Hmm, I wonder what this extra #2/0 goes to? Maybe I'll just tape it up and hope nobody notices.

As to the OP, I think you probably could use the three phase panel for your garage, but I agree with the other guys that I don't think it's the best idea. If for no other reason than when the inspector sees it he will wonder what else might be wrong. The worst thing that will happen though is that you'll have to replace it with a single phase panel if the inspector doesn't approve but you don't lose much by putting it in there to start with. It would go a long way to put an obvious label on the panel cover indicating 240/120V only. Leave the third phase unconnected and blank out those breaker spaces with plugs if they are open.
 
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Old 09-01-11, 07:23 PM
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Originally Posted by JerseyMatt
Code reference?
How about (2011) 110.3(A)(1), 110.12. It might even be a violation of the UL listing as it is intended to be installed as a three phase panel.
Exactly! I have yet to see a 3-phase loadcenter approved for use on a single phase system. It's definitely a violation of the U.L. approval.
 
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Old 09-02-11, 08:29 AM
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Not arguing that it isn't the wrong part for the job, but what if the panel were installed with intention to install a phase converter later on? Only one phase comes into it..
 
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Old 09-02-11, 05:57 PM
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Originally Posted by JerseyMatt View Post
Not arguing that it isn't the wrong part for the job, but what if the panel were installed with intention to install a phase converter later on? Only one phase comes into it..
I would think the inspector would say something like......fine, when you get the converter installed, call us for your inspection. Till that time, install a single phase panel for your housepower.
 
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Old 09-07-11, 08:08 PM
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One thing I should mention: I have sold many a used 3 phase panels on eBay and have gotten enough cash for them to purchase the single phase panel I posted AND a case of beer AND a steak. Just some food for thought.

Not arguing that it isn't the wrong part for the job, but what if the panel were installed with intention to install a phase converter later on? Only one phase comes into it..
In the case of using it with a phase converter, you would still need a disconnect. If I was doing that kind of job, I would feed the garage with a single phase feeder to a single phase panel. Then from the single phase panel you would install a feeder to the converter (breaker in single phase panel being your disconnect) Then converter to three phase panel. Then to your branch circuits.

IE: single phase panel>converter>3 phase panel
 
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Old 09-07-11, 11:42 PM
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One drawback about useing the phase converter is that it will be genrally wired in delta format and when you use the phase converter with single phase load do not use on manufactered leg due the voltage between the manufactered phase et netural will typically read 190 to 208 depending on set up.

{ note it very rare to see phase converter to run in wye format unless you have motour generator set up }


Merci,
Marc
 
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