Number of recepts on a 20A branch circuit

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shespuzzling

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Hi,

Trying to reconcile NEC 2008 210.21(B)(2) with 220.14(I), specifically Exhibit 220.4 which is in the 2008 Handbook. See attached for the two excerpts.

I had previously convinced myself that the maximum number of convenience outlets that could be on a single 20A branch circuit is 13. (180VA per outlet * 13 outlets = 2340VA, which is under 20A*120V=2400VA). This was under the assumption that the NEC prescribed load for convenience outlets already takes into account continuous vs non-continuous loading. Exhibit 220.4 also shows 13 outlets on a 20A branch circuit.

Now reading 210.21(B)(2) I'm not so sure. Has anybody else noticed this apparent contradiction? What's the actual max # of outlets on a 20A circuit?

Document1.jpg
 
If the max load allowed on a 20A branch circuit is 16A (per 210.21(b)(2)), then that means a maximum of (10) 180VA convenience outlets. However the exhibit referenced shows 13 convenience outlets, which would be a total ampacity of 19.5A at 120V.
 
ahhh got it, so the maximum indicated in 210.21(b)(2) is for a cord and plug connected load on a single receptacle? So even if I had a non-continuous cord and plug load rated at 20A, I'd have to use a 30A branch circuit and receptacle.
 
At the risk of being chastised again, I will restate my opinion, long held and frequently contradicted, that 210 and 220 don't speak with one another. The 180 VA per outlet is for calculating the minimum load for the building. It is not a design criterion. So my belief is that there are no limits to the number of outlets on a circuit, regardless of the occupancy. Specifically, when article 210.21(B) speaks of maximum loads, nothing requires us to count the outlet at 180 VA each. Instead, it is talking about what gets actually plugged into the outlet.

You may fire when ready, Gridley.
 
shespuzzling said:
ahhh got it, so the maximum indicated in 210.21(b)(2) is for a cord and plug connected load on a single receptacle? So even if I had a non-continuous cord and plug load rated at 20A, I'd have to use a 30A branch circuit and receptacle.
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No, a 20 amp or larger single receptacle on a 20 amp individual branch circuit can have a 20 amp non-continuous load.

210.22 Permissible Loads, Individual Branch Circuits.
An individual branch circuit shall be permitted to supply
any load for which it is rated, but in no case shall the load
exceed the branch-circuit ampere rating.
Click to expand...
 
But if you have convenience outlets and you're not designing for a particular cord and plug connected appliance you have to assume 180VA at a minimum, which would mean 13 outlets maximum.
 
charlie b said:
At the risk of being chastised again, I will restate my opinion, long held and frequently contradicted, that 210 and 220 don't speak with one another. The 180 VA per outlet is for calculating the minimum load for the building. It is not a design criterion. So my belief is that there are no limits to the number of outlets on a circuit, regardless of the occupancy. Specifically, when article 210.21(B) speaks of maximum loads, nothing requires us to count the outlet at 180 VA each. Instead, it is talking about what gets actually plugged into the outlet.

You may fire when ready, Gridley.
Click to expand...


I'll fire.

Article 220 is for calculating branch cir, feeders, services. Section 220.14(I) states 180va per receptacle but this section is under Part II which states Branch Circuit Load Calculation. So part II says branch circuit load calculation and 220.14(I) states 180 per receptacle then how do you reconcile your statement. IMO, it is saying that the branch circuit cannot have more than 180 va per receptacle.
 
shespuzzling said:
But if you have convenience outlets and you're not designing for a particular cord and plug connected appliance you have to assume 180VA at a minimum, which would mean 13 outlets maximum.
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Disagree. Load calcs and load usage are not the same thing. If they were, you could argue that every 20a receptacle circuit is allowed to supply 13 receptacles.

Added: You aren't assuming that each receptacle will actually be loaded at 180va when you allow for it when doing load calcs. There's no guarantee that 180va will ever be exceeded or not exceeded.
 
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charlie b said:
You may fire when ready, Gridley.
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I'm ready to fire with you, as I agree with you completely. For example, I would have no concern with placing more than 10 or 13 Christmas lighting receptacles on a single 15a or 20a circuit, respectively.
 
LarryFine said:
Disagree. Load calcs and load usage are not the same thing. If they were, you could argue that every 20a receptacle circuit is allowed to supply 13 receptacles.

Added: You aren't assuming that each receptacle will actually be loaded at 180va when you allow for it when doing load calcs. There's no guarantee that 180va will ever be exceeded or not exceeded.
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What value would you use then to calculate the load on a branch circuit serving convenience outlets? And are you suggesting that the exhibit in the handbook which indicates 13 outlets max on a 20A is incorrect?
 
shespuzzling said:
What value would you use then to calculate the load on a branch circuit serving convenience outlets?
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To calculate, as for service load calcs, I'd use 180va. To actually decide how to load them, i.e. assign circuits, it depends.

In a residential kitchen, for example, general-use countertop receptacles, typically two or three per circuit; for known appliances, like microwave and refrigerator, one per circuit.

In a commercial hallway, where the janitorial staff needs to plug in the floor buffer, I would place more than 13 on a 20a circuit if there was enough hallway to warrant that many.

And are you suggesting that the exhibit in the handbook which indicates 13 outlets max on a 20A is incorrect?
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I am, especially if the handbook is not an enforceable part of the NEC.
 
Dennis Alwon said:
So part II says branch circuit load calculation and 220.14(I) states 180 per receptacle then how do you reconcile your statement.
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By noting that everything you said has to do with article 220. That is all about calculating load, so that any given branch circuit, or feeder, or service will have enough capacity to handle what will be served by it. It is not about making design decisions of how many branch circuits are needed, or what can be connected to any single branch circuit. I like Larry’s example of a building with long hallways. The janitor’s vacuum cleaner or floor buffer will be plugged into only one outlet at a time, so it does not matter how many outlets are on the same circuit.
Dennis Alwon said:
IMO, it is saying that the branch circuit cannot have more than 180 va per receptacle.
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How, then, can we allow a person in my building (office type) to ride a bike to work, take a shower, and plug a 1200 watt hair dryer into an outlet in the locker room? Since I know that is possible, I won’t choose to design the building with a large number of locker room outlets on the same circuit. But if I know enough about the likely use of outlets, I can make my own design decisions about how many outlets to put on the same circuit.

I say again, a different way this time: 210 is 210, and 220 is 220, and never the twain shall meet. (OK, now I owe apologies for misquoting both Rudyard Kipling and Admiral George Dewey.)
 
Here's what confuses me. Last week you guys had mostly convinced me that a duplex receptacle was two outlets. And this graphic shows otherwise. What am I missing?
 
MAC702 said:
Here's what confuses me. Last week you guys had mostly convinced me that a duplex receptacle was two outlets. And this graphic shows otherwise. What am I missing?
Click to expand...

It goes by the yoke. 1 yoke= 1 receptacle, doesn't matter how many plugs you can stick into it. Single, duplex or triple counts as ONE receptacle.

-Hal
 
charlie b said:
At the risk of being chastised again, I will restate my opinion, long held and frequently contradicted, that 210 and 220 don't speak with one another. The 180 VA per outlet is for calculating the minimum load for the building. It is not a design criterion. So my belief is that there are no limits to the number of outlets on a circuit, regardless of the occupancy. Specifically, when article 210.21(B) speaks of maximum loads, nothing requires us to count the outlet at 180 VA each. Instead, it is talking about what gets actually plugged into the outlet.

You may fire when ready, Gridley.
Click to expand...

Fire at me also, I agree with Charlie here.

You can have two receptacles on the circuit but plug in two items that draw more than 20 amps combined and that 180 VA per receptacle means nothing. Plug in 100 small desktop items that only draw millamps each and you may never blow the 20 amp breaker either. This is design issue more than code requirements, or should be anyway.
 
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