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#204689 - 12/30/11 12:49 AM How Many Receptacles  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Interesting question came my way and I'd like to share it with all: How many general purpose receptacles can we install on a 120v. 20a. circuit in an office suite? Need code references please.


George Little

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#204691 - 12/30/11 02:04 AM Re: How Many Receptacles [Re: George Little]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
220.14(K) gives you two choices

(1) is you kick back to 214.14(I) "receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke."
(the good old "commercial" rule)

*or*

(2)11 volt-amperes/m2 or 1 volt-ampere/ft2 (similar to the dwelling rule where there is no limit)

I would want them to put a note on the plan about which option they used. Whether you want to reject on that is probably how busy you are
Assuming you run the numbers, if neither option worked out
it would go back.



Greg Fretwell

#204694 - 12/30/11 11:48 AM Re: How Many Receptacles [Re: George Little]  
George Little  Offline
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Joined: Jan 2004
Posts: 1,489
Michigan USA
Let me rephrase that Greg, How many duplex receptacles can I put on a 20a. 120v. circuit in other than a residential occupancy?


George Little

#204696 - 12/30/11 12:49 PM Re: How Many Receptacles [Re: George Little]  
KJay  Offline
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Joined: Nov 2007
Posts: 763
MA, USA
Greg already mentioned the other part that is needed to calculate this for banks and office buildings. 220.14[K], says we are supposed to use the larger of the two for the branch circuit load calcs.

But for the first part, according to 220.14[I], shouldn’t it go by the yoke and not the actual type or number of receptacles? A single, duplex or even an old Despard type triplex receptacle that is all on the same yoke should normally count as one receptacle at 180VA or 180W each.
So, in that case 20A X 120V = 2400W and 2400W/180VA = 13.3 then using the standard of less than 5 round down, 13 single, duplex or triplex receptacles on a 20A branch circuit.
Is this not how others would calculate this portion?



#204698 - 12/30/11 01:44 PM Re: How Many Receptacles [Re: George Little]  
George Little  Offline
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Joined: Jan 2004
Posts: 1,489
Michigan USA
KJay, I agree with your part about the 13 receptacles 100%. I think 220.14(K) is used for calculating load on a feeder or service but 220.14(I) is used when talking about or calculating the load on a branch circuit. That seems to be the issue here and I'm wondering what the rest of the gang thinks.


George Little

#204700 - 12/30/11 03:27 PM Re: How Many Receptacles [Re: George Little]  
KJay  Offline
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Joined: Nov 2007
Posts: 763
MA, USA
I’m not sure I understand, but both 220.14[I] and 220.14[K] are located in Part II of Art. 220, "Branch-Circuit Load Calculation". At least they are in the 2011 NEC, but then again, that’s the only one I have access to these days.


#204702 - 12/30/11 04:59 PM Re: How Many Receptacles [Re: George Little]  
gfretwell  Offline


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Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
Originally Posted by George Little
KJay, I agree with your part about the 13 receptacles 100%. I think 220.14(K) is used for calculating load on a feeder or service but 220.14(I) is used when talking about or calculating the load on a branch circuit. That seems to be the issue here and I'm wondering what the rest of the gang thinks.


220.14 is included in part II, "Branch Circuit Calculations".

I don't see where is says "feeder"


Greg Fretwell

#204703 - 12/30/11 06:18 PM Re: How Many Receptacles [Re: George Little]  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Greg— I respectfully don't agree with the assumption that one can put as many receptacles as they want to on a 20a. 120v. circuit. I think you are limited to 13 receptacles on said circuit. After all they are required to be calculated as 180va. each yoke per (I). Also look at 220.44.
This is a valid issue when you make a plan review or an inspection.


George Little

#204704 - 12/30/11 07:27 PM Re: How Many Receptacles [Re: George Little]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
I agree, I missed the "larger of" or simply misunderstood what they were trying to say.

(2) will actually cause more receptacle circuits, not allow more receptacles on one.

My bad.



Greg Fretwell


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