220.18 maximum load

[Strathead]

Here is a mind twister to me. I was floored the other day, when I was discussing and (I now believe mistakenly) was lead to believe that the code doesn't limit the number of light fixtures on a branch circuit in a dwelling unit. Correct me if I am wrong, but right here, people have contended that there is no limit to the number of receptacles on a branch circuit in a dwelling unit? I was hung up on this for a couple days, but have come to this conclusion:

220.18 states that the total load shall not exceed the rating of a the branch circuit. Even though the code calculations for 220.12 show the minimum number of branch circuits that can feed a dwelling unit, they don't supersede 220.18 so there has to be a determination of the impact of each outlet on any one branch circuit. You can't count a duplex as zero amps just because nothing is plugged in to it at the time. So I contend that the 90va per single receptacle of 180va per duplex is required by code, just like 150va per 2 feet of track and the maximum lamp wattage of a fixture and all of the other load guidelines in article 220.

So my questions: Am I remembering correctly that it has been contended here that you don't have to limit the number of duplexes on say a 20 amp dwelling unit branch circuit. If so, those that feel that way. what is your position on what I wrote above.

After reading this a couple times I contend that you do, in fact, have to limit the number of duplexes on a branch circuit to the factor of 180va per. And if you don't, do you believe you can put an unlimited number of can lights on a dwelling unit circuit as well?

 

[david luchini]

I think 210.11(B) addresses your dilemma, together with 220.14(J).

I see no reason to calculate a "load" for each receptacle in residential applications.

 

[Strathead]

I think 210.11(B) addresses your dilemma, together with 220.14(J).

I see no reason to calculate a "load" for each receptacle in residential applications.

Not really IMO. You still have to ensure that you don't overload an individual circuit. And while a typical track home wouldn't have this issue, a fancy mansion could. For the feeder fine, but for the branch circuits I believe we have the responsibility to ensure they comply with 220.18 and that would mean no more than 13 duplexes on a 20 amp circuit.

 

[david luchini]

Not really IMO. You still have to ensure that you don't overload an individual circuit. And while a typical track home wouldn't have this issue, a fancy mansion could. For the feeder fine, but for the branch circuits I believe we have the responsibility to ensure they comply with 220.18 and that would mean no more than 13 duplexes on a 20 amp circuit.

And what if a homeowner decided to put 2A of load on each of the 13 duplexes on a 20A circuit? There is no way to ensure that a receptacle circuit is not overloaded.

If the total load is 24000 VA, and the minimum required 10 branch circuits are installed, and the load is "evenly proportioned" among those 10 branch circuits, then how could any of them exceed their rating?

If you are concerned about it, install more than the minimum required branch circuits.

 

[roger]

I agree with David and here is Mikes take on it.

Q6. Is there a maximum number of duplex outlets on a 20A Circuit?
A6. For dwelling units there is no maximum number [220.14(J)]. For nondwelling applications, each 15A or 20A, 125V general-use receptacle outlet is considered as a 180 VA per mounting strap. With that said, the maximum number of 15A or 20A, 125V receptacles on a 20A circuit is 13.
Circuit VA = Volts x Amperes
Circuit VA = 120V x 20A
Circuit VA = 2,400 VA
Number of Receptacles = 2,400 VA/180 VA
Number of Receptacles = 13

IMO, the NEC takes into consideration that it would be better to allow an unlimited number of receptacles on a circuit rather than have to rely on extension cords to make up for a limited number. In my house the same number of utilization equipment (load) is pretty much set in each room however, the furniture layout moves whenever she gets an inkling and it makes sense to have receptacles waiting to be used.

Roger

 

[charlie b]

My take is that the process of calculating how much load must be allocated for a building is independent of the process of designing the branch circuits for that building. Rudyard Kipling wrote, "East is East and West is West, and never the twain shall meet." We can say the same about 210 and 220. Article 210 gives me a minimum number of branch circuits and tells me where certain ones must go. But I can put in more, if I wish. Article 220 tells me I need to account for 180 VA for any outlet that is not designated for use by a specific appliance. But I can assign a higher load, if I wish. When I design a room's outlet layout, I will limit the number of receptacles on a given circuit. But I do that because I choose to, because I don't want the owner or tenant to be unhappy about circuits tripping, not because any load calculation in 220 establishes a limit on the design of a circuit that is called for in 210.

This question has been debated in this forum several times. I don't think there has been a concensus. I do recall not getting a great deal of support for the point of view I outline above. That does not concern me.

 

[ActionDave]

So my questions: Am I remembering correctly that it has been contended here that you don't have to limit the number of duplexes on say a 20 amp dwelling unit branch circuit. If so, those that feel that way. what is your position on what I wrote above.

There is no limit on the number of duplex recepts you can put on a general lighting circuit. It is a design issue.

I have worked on my fair share of McMansions. Yea, the rooms are big, yea, there is a lot of them. Nobody that I have seen outfits all those extra bedrooms and dens with a bunch of high wattage fixtures. Table lamps, clock radios, digital picture viewers, sure. Toaster ovens, microwaves, coffee pots, hair dryers and curling irons in the living areas; not so much. Truth is big houses are the same as small houses, more power gets used in the kitchen and the bathroom in the morning than gets used in the whole house the rest of the day and night.

After reading this a couple times I contend that you do, in fact, have to limit the number of duplexes on a branch circuit to the factor of 180va per. And if you don't, do you believe you can put an unlimited number of can lights on a dwelling unit circuit as well?

No, you can't put an unlimited number of can lights on a single circuit. There is a big difference between putting more lights on one switch than the circuit can hold vs. putting extra recepts in a room just to make it more convenient for the HO to have places to plug in a table lamp or digital picture viewer and his favourite lava lamp.

 

[Strathead]

There is no limit on the number of duplex recepts you can put on a general lighting circuit. It is a design issue.

I have worked on my fair share of McMansions. Yea, the rooms are big, yea, there is a lot of them. Nobody that I have seen outfits all those extra bedrooms and dens with a bunch of high wattage fixtures. Table lamps, clock radios, digital picture viewers, sure. Toaster ovens, microwaves, coffee pots, hair dryers and curling irons in the living areas; not so much. Truth is big houses are the same as small houses, more power gets used in the kitchen and the bathroom in the morning than gets used in the whole house the rest of the day and night.
No, you can't put an unlimited number of can lights on a single circuit. There is a big difference between putting more lights on one switch than the circuit can hold vs. putting extra recepts in a room just to make it more convenient for the HO to have places to plug in a table lamp or digital picture viewer and his favourite lava lamp.

So what if I put 11 can lights on the circuit, then how many receptacles can I put on the circuit? Or If I put 12 can lights on it? Again, tell me why you don't have to assign some value to a duplex to comply with 220.18? Do you contend the same unlimited argument for receptacle?

 

[Strathead]

My take is that the process of calculating how much load must be allocated for a building is independent of the process of designing the branch circuits for that building. Rudyard Kipling wrote, "East is East and West is West, and never the twain shall meet." We can say the same about 210 and 220. Article 210 gives me a minimum number of branch circuits and tells me where certain ones must go. But I can put in more, if I wish. Article 220 tells me I need to account for 180 VA for any outlet that is not designated for use by a specific appliance. But I can assign a higher load, if I wish. When I design a room's outlet layout, I will limit the number of receptacles on a given circuit. But I do that because I choose to, because I don't want the owner or tenant to be unhappy about circuits tripping, not because any load calculation in 220 establishes a limit on the design of a circuit that is called for in 210.

This question has been debated in this forum several times. I don't think there has been a concensus. I do recall not getting a great deal of support for the point of view I outline above. That does not concern me.

As a PE, you can follow your own guideline, and I don't think even those who dispute that you don't have to limit the number, still limit it because it is the right thing to do. You have some support for your view now, and I am glad that I have at least one. With all of the over the top things in the code, like arc fault and such, it is surprising to me that people would think they can just put an unlimited number of recepts on a circuit. On the flip side, I see the argument that you could put two welding receptacles on the same 50 amp circuit if you were going to move the welder from one place to another, but that can be dealt with with signage.

 

[takelly]

You can not put as many lighting outlets on a circuit as you want. Luminaires are not receptacles.
220.14 (D) Luminaires. An outlet supplying luminaire( s) shall be calculated based on the maximum volt-ampere rating of the equipment and lamps for which the luminaire( s) is rated.

 

[Strathead]

You can not put as many lighting outlets on a circuit as you want. Luminaires are not receptacles.
220.14 (D) Luminaires. An outlet supplying luminaire( s) shall be calculated based on the maximum volt-ampere rating of the equipment and lamps for which the luminaire( s) is rated.

Like I said don't, put 12 of them on the circuit at 150VA is 1800 VA continuous, then put twenty duplexes or so on the same circuit. Nothing wrong with that, right?

article 220 also assigns 180va for duplexes and doesn't specifically assign or nix that from residential duplexes. Again, duplexes have to count for something in a branch circuit. 220.18 must be complied with. One of you defending the unlimited duplexes on a circuit, please address exactly how you justify that in the context of 220.18, or do you believe 220.18 doesn't apply to residential branch circuit with duplexes on it? As you obviously believe it applies to a residential circuit with only can lights on it.

 

[roger]

Like I said don't, put 12 of them on the circuit at 150VA is 1800 VA continuous, then put twenty duplexes or so on the same circuit. Nothing wrong with that, right?

Correct however, once you put a known load on a circuit you should consider it when adding outlets.

article 220 also assigns 180va for duplexes and doesn't specifically assign or nix that from residential duplexes.

220.14(J) does in fact tell us that we don't need to worry about them in dwelling units.

(J) Dwelling Occupancies.
In one-family, two-family, and
multifamily dwellings and in guest rooms or guest suites of
hotels and motels, the outlets specified in (J)(1), (J)(2), and
(J)(3) are included in the general lighting load calculations
of 220.12. No additional load calculations shall be required
for such outlets.

Roger

 

[don_resqcapt19]

Assuming the circuit is installed and protected per the rules in the NEC, the only danger of an overloaded circuit is an irate customer. It is not a safety or code issue.

 

[kwired]

Assuming the circuit is installed and protected per the rules in the NEC, the only danger of an overloaded circuit is an irate customer. It is not a safety or code issue.

That is how I approach it. Even in non dwellings you can get away with some things if you take actual load into consideration whether you actually comply with code or not. I see the 180 VA per outlet as somewhat a game with inspectors/code more so then a realistic look at actual load. One outlet may only see 10VA, another one may see 1500, plan carefully.

Should you misjudge what will be plugged in - overcurrent protection kicks in.

 

[ActionDave]

So what if I put 11 can lights on the circuit, then how many receptacles can I put on the circuit? Or If I put 12 can lights on it? Again, tell me why you don't have to assign some value to a duplex to comply with 220.18? Do you contend the same unlimited argument for receptacle?

I contend the code is meant to ensure safety, not be an antidote to stupidity.

More can lights means more load on a circuit. More recpts does not mean more load on a circuit. A hundred recepts in a room does not mean one hundred things are going to be plugged in, it just means the HO a lot of choice where to plug in a table lamp.

 

[Strathead]

Correct however, once you put a known load on a circuit you should consider it when adding outlets.

220.14(J) does in fact tell us that we don't need to worry about them in dwelling units.



Roger

I can't agree or disagree, so as devil's advocate, I contend that 220.14(J) doesn't negate 220.18 so you still need to concern yourself with how many receptacle are on a circuit. Also, can't find it right now, but there is a code that states the circuits shall be evenly divided. You can't comply with that without assigning some value to receptacles.

 

[Strathead]

Assuming the circuit is installed and protected per the rules in the NEC, the only danger of an overloaded circuit is an irate customer. It is not a safety or code issue.

But a circuit that violates 220.18 violates the code. That is a catch 22.

 

[ActionDave]

But a circuit that violates 220.18 violates the code. That is a catch 22.

No catch 22. The number of recpts on a circuit does in no way govern the maximum load it will see.

 

[jumper]

Also, can't find it right now, but there is a code that states the circuits shall be evenly divided.

You are thinking of 210.11

You can't comply with that without assigning some value to receptacles.

For a dwelling unit you can. There is no direct assigned value.


This what MH says:

Number of circuits

There’s no maximum number of receptacles on a dwelling unit circuit. But how do you determine the minimum number of circuits for general lighting and general-use receptacles? Divide the total calculated load in amperes by the ampere rating of the circuits used [210.11]. See Example D1(a) in Annex D. If you calculate the total load based on VA/square foot, ensure the individual loads are evenly proportioned among multioutlet branch circuits within the panel board.

http://ecmweb.com/code-basics/branch-circuits-part-1

 

[petersonra]

Assuming the circuit is installed and protected per the rules in the NEC, the only danger of an overloaded circuit is an irate customer. It is not a safety or code issue.

bingo!