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Old 11-22-2009, 06:50 PM   #1
Steevo
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Default How many 20A convenience receptacles on a breaker?

How many 20A duplex receptacles, wired with 12/2 romex, would you put on a single 20A breaker?
I just installed 18 boxes along the walls above workbench height, and I ran the 12/2 romex from box to box, then a homerun back to the panel for a breaker at every six boxes. The neighbor looked at it and said he would have put them all on one. I think 18 is too many for one run, but is six on a run overkill?
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Old 11-22-2009, 06:55 PM   #2
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Default Re: How many 20A convenience receptacles on a breaker?

per code the load to use for calculations is 180VA/recept.
you can load a 20A circuit up to 16A
16 x 120/180 ~ 10.7, round down to 10...
I usually put no more than 8...

it depends what you are hooking up
it sounds like you did a good layout...
I might have used 3 also, maybe 2, and alternated the boxes on the circuits
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Old 11-22-2009, 06:59 PM   #3
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Default Re: How many 20A convenience receptacles on a breaker?

If this is residential, no limit, they are convenience outlets. It is like an extension cord and you are most likely only using one or two at a time. If it were commercial that would be a different story.

You can run 1/2 on one leg and other 1/2 on the second leg using the common neutral on you home run circuit.

Last edited by porschedude996TT; 11-22-2009 at 07:02 PM.
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Old 11-22-2009, 07:19 PM   #4
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Default Re: How many 20A convenience receptacles on a breaker?

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Originally Posted by Schrodingers Cat View Post
per code the load to use for calculations is 180VA/recept.
you can load a 20A circuit up to 16A
16 x 120/180 ~ 10.7, round down to 10...
I usually put no more than 8...
For residential?, are these outlets for continuous loads? I think not
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Old 11-22-2009, 07:23 PM   #5
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Default Re: How many 20A convenience receptacles on a breaker?

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For residential?, are these outlets for continuous loads? I think not
Convenience outlets are not continous. Most of the receptacles are are not used continous use. They are not like a dedicated circuit like a fridge or a washer.

I have two 20amp circuits in my shop that have 13 20 amp receptacles on them. One circuit that is a little longer than the other is wired with 10awg and the other has 12awg. My thinking was that the one with the may have a greater load on it and didn't want a voltage drop on it.

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Old 11-22-2009, 07:29 PM   #6
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Default Re: How many 20A convenience receptacles on a breaker?

I would be surprised if I ever had more than two outlets in use together. One guy can only operate so many power tools at one time. Even if I left the bench grinder spinning, and the parts washer running, and stepped over to the drill press to punch a hole in something, that is only three at a time. I might have several cordless tool batteries on chargers as once, but that would likely be off a single receptacle with a power strip for a battery charging shelf. I guess the only continuous load would be a small fridge under the bench. I just wanted a receptacle every four feet or less along the primary work area walls where I will have benches, etc.

Last edited by Steevo; 11-22-2009 at 07:32 PM.
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Old 11-22-2009, 07:31 PM   #7
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Default Re: How many 20A convenience receptacles on a breaker?

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Convenience outlets are not continous. .
I might have been a little sarcastic in my response, tough to tell on here though
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Old 11-22-2009, 07:33 PM   #8
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Default Re: How many 20A convenience receptacles on a breaker?

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I would be surprised if I ever had more than two outlets in use together. One guy can only operate so many power tools at one time. Even if I left the bench grinder spinning, and the parts washer running, and stepped over to the drill press to punch a hole in something, that is only three at a time. I might have several cordless tool batteries on chargers as once, but that would likely be off a single receptacle with a power strip for a battery charging shelf. I guess the only continuous load would be a small fridge under the bench. I just wanted a receptacle every four feet or less along the primary work area walls where I will have benches, etc.
What you did is fine, its not overkill if thats how you want it.
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Old 11-22-2009, 07:34 PM   #9
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Default Re: How many 20A convenience receptacles on a breaker?

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I would be surprised if I ever had more than two outlets in use together. One guy can only operate so many power tools at one time. Even if I left the bench grinder spinning, and the parts washer running, and stepped over to the drill press to punch a hole in something, that is only three at a time. I might have several cordless tool batteries on chargers as once, but that would likely be off a single receptacle with a power strip for a battery charging shelf. I just wanted a receptacle every four feet or less along the primary work area walls where I will have benches, etc.
Exactly, convenience Outlets. One guy can only run a couple of tools at a time. If it were a commercial application they would require you to budget power to each dedicated machine using a separate circuit.
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Old 11-22-2009, 10:19 PM   #10
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Default Re: How many 20A convenience receptacles on a breaker?

Thanks, everyone, I appreciate the feedback.
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Old 11-22-2009, 10:58 PM   #11
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Default Re: How many 20A convenience receptacles on a breaker?

You may only plan to use 2 or 3 at any given point, but needs change - and owners change. A future owner might see that you have 20 outlets and decide to use them all - or your needs might change down the road to where you require more amperage, so if anything I'd recommend planning ahead.

There may not be any written rule saying you can't have any more than 10 devices per circuit, but based upon loads I think the general rule of thumb is 10 receptacles for 15A or 13 receptacles for 20A. I guess when I'm doing the work I never exceed 10 devices per circuit, and if I find myself in a position where I will have 15 devices, I split them evenly between two. In the scope of things, this really isn't an area I wish to cut corners and it is always easier and cheaper to do things right the first time.
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Old 11-22-2009, 11:58 PM   #12
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Default Re: How many 20A convenience receptacles on a breaker?

I would not worry about some future owner as far as the number of receptacles on a circuit. Keep the number reasonable for your use. If some future owner loads up all the outlets he will pop the breaker. At that point he can hire an electrician to split the circuits or rewire as he sees fit.
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Old 11-23-2009, 02:05 PM   #13
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Default Re: How many 20A convenience receptacles on a breaker?

The other thing to think about is what happens when you do trip a circuit breaker. I have my computer/radio/etc on a separate breaker so my computer doesn't reset.
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Old 11-23-2009, 02:47 PM   #14
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Default Re: How many 20A convenience receptacles on a breaker?

Steevo keep in mind that 12/2 WG is rated at 20 amp. If you use 20 amp rated receptacle you can rate them at full ampere. You will note that 15 amp rec. in quick wire only take 14/2, all 20 amp 120v have screw terminals. In my shop I used #12 with all 20 amp rec. because of the load deversity you can have all of them one one circuit. First check your City or State codes. I put every six 20 amp rec. on one 20 amp breaker. In a garage line lose is minimal. Always remember that motor circuits need to be calculated on the horse power and full load amps. Remember that a motor starts a five times the full load current.
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Old 11-23-2009, 04:38 PM   #15
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Default Re: How many 20A convenience receptacles on a breaker?

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Steevo keep in mind that 12/2 WG is rated at 20 amp. If you use 20 amp rated receptacle you can rate them at full ampere. You will note that 15 amp rec. in quick wire only take 14/2, all 20 amp 120v have screw terminals. In my shop I used #12 with all 20 amp rec. because of the load deversity you can have all of them one one circuit. First check your City or State codes. I put every six 20 amp rec. on one 20 amp breaker. In a garage line lose is minimal. Always remember that motor circuits need to be calculated on the horse power and full load amps. Remember that a motor starts a five times the full load current.
Amen to that, coyote66.
20A all the way.
No stab connected receptacles here, all will be 20A screw-term for full capacity capability.
It sounds like, at 6 per breaker, I am well covered.
Thanks everyone.
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Old 11-23-2009, 05:53 PM   #16
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Default Re: How many 20A convenience receptacles on a breaker?

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I think 18 is too many for one run, but is six on a run overkill?
I'm not an electrician (although I play one on TV), regardless of the type of project, I always make efforts to error on overkill as opposed to questionable/borderline, when time, materials and $$$ allow of course If that's what you want to do, your panel supports it, you can run the proper wire, maintain safety and comply with code, then why not?
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Old 11-25-2009, 12:32 AM   #17
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Default Re: How many 20A convenience receptacles on a breaker?

I've been installing a lot of new circuits/wiring in my shop, since the entire place only had 2 outlets. I've been running two or 3 20A outlets per breaker. As others have said you can have as many as you want though, just like plugging in a big power strip.

I'm only 1 guy so I can't use much at once, but, I like to leave one dedicated circuit for my air compressor, another for a small heater, another for some extra lights, and some extras for whatever. All those things could potentially be on at once in my shop, but everybody is different...

As far as I'm concerned you can't have too many dedicated outlets/circuits, but 10-12ga copper wire cost so freakin' much these days...
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Old 11-25-2009, 05:12 AM   #18
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Default Re: How many 20A convenience receptacles on a breaker?

I like to run each "wall" in the shop on a separate breaker. Then I use dedicated circuits for certain tools and appliances. That way I can easily label and find breakers in the panel. The overhead lights are always on their own circuit with an emergency light. Task lighting can use the wall outlets.

Of course BIG shops may need multiple circuits per wall.
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Old 11-25-2009, 05:32 AM   #19
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Default Re: How many 20A convenience receptacles on a breaker?

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That way I can easily label and find breakers in the panel.
Yeah, that's a great thing to do in a shop/garage. I have labeled every cover plate on every outlet/switch in the place with a number corresponding to the breaker. Thinking about painting the cover plate for each 20A circuit a different color for easy reference.
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