gregsparky
Member
IN AN INDUSTRIAL APPLICATION, HOW MANY GENERAL USE RECEPTACLES ARE ALLOWED ON A 20 AMP/120 VOLT CIRCUIT?
HOW MANY?
- Thread starter gregsparky
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Re: HOW MANY?
I figured that would be the answer. I'm not the OP, but I have a question to which I have seen conflicting answers: Does the 180va take into account the 80% rule, or do you have derate the circuit by 20% (allow 20% headroom)?
Bottom line is the correct answer:
A. 10 (13 minus 20%)
B. 13 (13 minus 0%)
../Wayne C.
PS: My early wiring days go back far enough that we called 120-volts 110-volts in which case a 20-amp circuit was about 2000 watts (rounding down). I got it in my head early on for residential work that each general purpose lighting outlet had to be figured at 1.5 amps (imprecise). Even with such imprecise calculations the answer came out to 13.33 outlets per lighting circuit. I would round down further to 12. It's curious to me that my rule of thumb actually wasn't too far off the non-residential code.
[ September 13, 2003, 01:43 PM: Message edited by: awwt ]
I figured that would be the answer. I'm not the OP, but I have a question to which I have seen conflicting answers: Does the 180va take into account the 80% rule, or do you have derate the circuit by 20% (allow 20% headroom)?
Bottom line is the correct answer:
A. 10 (13 minus 20%)
B. 13 (13 minus 0%)
../Wayne C.
PS: My early wiring days go back far enough that we called 120-volts 110-volts in which case a 20-amp circuit was about 2000 watts (rounding down). I got it in my head early on for residential work that each general purpose lighting outlet had to be figured at 1.5 amps (imprecise). Even with such imprecise calculations the answer came out to 13.33 outlets per lighting circuit. I would round down further to 12. It's curious to me that my rule of thumb actually wasn't too far off the non-residential code.
[ September 13, 2003, 01:43 PM: Message edited by: awwt ]
big john
Senior Member
- Location
- Portland, ME
Re: HOW MANY?
I also interpret the eighty percent loading rule to apply to the connected device.
Though I have seen some cases where the following didn't apply, I'm told part of the UL listing actually works to ensure that:
Using 15A recepticals as an example; if you have a device that draws more than 12A (80% of 15) then it should be equiped with a plug designed to only fit 20A receps.
-John
I also interpret the eighty percent loading rule to apply to the connected device.
Though I have seen some cases where the following didn't apply, I'm told part of the UL listing actually works to ensure that:
Using 15A recepticals as an example; if you have a device that draws more than 12A (80% of 15) then it should be equiped with a plug designed to only fit 20A receps.
-John
gregsparky
Member
Re: HOW MANY?
I AM LOOKING FOR THE SECTION IN THE CODE BOOK THAT TELLS US HOW MANY RECEPTACLES CAN BE INSTALLED ON A GENERAL DUTY RECEPTACLE CIRCUIT IN AN "INDUSTRIAL" APPLICATION? I QUESS I THOUGHT I KNEW THE ANSWER BUT MAYBE NOT. I THOUGHT THERE WAS NO SET AMOUNT. REMEMBER NOW, I'M NOT CALCULATING A LOAD ON THE CIRCUIT, I'M JUST ADDING PLUGS AS I GO. IS THERE A MAXIMUM?
I AM LOOKING FOR THE SECTION IN THE CODE BOOK THAT TELLS US HOW MANY RECEPTACLES CAN BE INSTALLED ON A GENERAL DUTY RECEPTACLE CIRCUIT IN AN "INDUSTRIAL" APPLICATION? I QUESS I THOUGHT I KNEW THE ANSWER BUT MAYBE NOT. I THOUGHT THERE WAS NO SET AMOUNT. REMEMBER NOW, I'M NOT CALCULATING A LOAD ON THE CIRCUIT, I'M JUST ADDING PLUGS AS I GO. IS THERE A MAXIMUM?
Re: HOW MANY?
In a dwelling unit there isn't a limit on the number of receptacles on a branch circuit. In a industrial application it is computed at 180 va per receptacle. I have a reference book that gives this figure but I don't have it with me at this time. You can look in the 2002 NEC 220.3 (B)(9). Receptacle outlets shall be computed at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. Then again like most things it would depend on the inspector you had at the moment.
In a dwelling unit there isn't a limit on the number of receptacles on a branch circuit. In a industrial application it is computed at 180 va per receptacle. I have a reference book that gives this figure but I don't have it with me at this time. You can look in the 2002 NEC 220.3 (B)(9). Receptacle outlets shall be computed at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. Then again like most things it would depend on the inspector you had at the moment.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: HOW MANY?
Keep in mind local codes and ordinances may apply, it may be less than 13.
Keep in mind local codes and ordinances may apply, it may be less than 13.
david
Senior Member
- Location
- Pennsylvania
Re: HOW MANY?
[ September 14, 2003, 01:02 PM: Message edited by: david ]
[ September 14, 2003, 01:02 PM: Message edited by: david ]
russ
Senior Member
- Location
- Burbank IL
Re: HOW MANY?
With no known load, I would say 13, just like mclain laid it out.
If there were a known load, it could not exceed the branch circuit rating.
If it were a continuous load, then the circuit would be required to be rated at 125% of the load.
Sometimes it's not as easy as blanket numbers.
It would depend on the use of the receptacles.
Russ
[ September 14, 2003, 03:44 PM: Message edited by: russ ]
With no known load, I would say 13, just like mclain laid it out.
If there were a known load, it could not exceed the branch circuit rating.
If it were a continuous load, then the circuit would be required to be rated at 125% of the load.
Sometimes it's not as easy as blanket numbers.
It would depend on the use of the receptacles.
Russ
[ September 14, 2003, 03:44 PM: Message edited by: russ ]
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