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charlie b

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I infer that you are talking about the standard 120 volt, 15 or 20 amp receptacle outlets. My answer is ?No.? We don?t know what will be plugged into a receptacle, and we don?t know if that load will be on for over three hours.

By the way, adding 25% for continuous loads is not a "demand factor." I don't even think it shows up in article 220.
 

radiopet

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Spotsylvania, VA
Les,

Are you speaking of a Dedicated Circuit to a receptacle that will have a cont. load on it?

Is that what you are asking.....or are assuming as charlie has stated that a receptacle will have a cont. load...?

Clarity may help answer your question.
 
Confused

Confused

I am designing a large mfg. area. My question is that do you apply demand factors on recpt.loads of Table 220.13 ( 2002 code ) if the loads are continuous.

Les
 

charlie b

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My answer remains the same. Add up the receptacles at 1800 VA each, and do not adjust for the possibility that any load may be continuous. Then you have two choices. One choice is to add in the other two things they mention in paragraph 220.13, and finally apply the demand factors in Table 220.11. The other choice is to treat the receptacle loads separate from the other two items, and apply the demand factors in Table 220.13. In neither case does the concept of ?continuous loads? come into play.
 

radiopet

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Spotsylvania, VA
I agree with Charlie here.....you have not defined why they would be continuous..usually something defined as continuous like they are saying a dedicated circuit to a receptacle that will run a piece of dedicated equipment per se' that is a continuous load....but not general receptacle locations as you have stated.
 

haskindm

Senior Member
Location
Maryland
In order for continuous load to be considered, the circuit must be near its capacity and the load must be on for 3-hours or more. A 20-amp circuit with one 60-watt lamp plugged into it that stays on 24-hours per day seven days per week would not be considered a continuous load. Anything that is controlled by a thermostat and plugs in, such as a refrigerator, or microwave, is not considered a continuous load. The list of equipment that is cord-and-plug connected and a continuous load is fairly short. Most cord and plug connected equipment is designed to be portable and easily exchanged. If you do have permanent equipment that is a continuous load, perhaps some thought should be given to hard-wiring the equipment, rather than plugging it in.
 

augie47

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continuous load

continuous load

haskindm said:
In order for continuous load to be considered, the circuit must be near its capacity and the load must be on for 3-hours or more. A 20-amp circuit with one 60-watt lamp plugged into it that stays on 24-hours per day seven days per week would not be considered a continuous load. Anything that is controlled by a thermostat and plugs in, such as a refrigerator, or microwave, is not considered a continuous load. The list of equipment that is cord-and-plug connected and a continuous load is fairly short. Most cord and plug connected equipment is designed to be portable and easily exchanged. If you do have permanent equipment that is a continuous load, perhaps some thought should be given to hard-wiring the equipment, rather than plugging it in.

Huh? I beg to differ. One may choose not wish to "consider" a load until the
circuit is near capacity, howver, by definition, that 60 watt lamp, once it is on for 3 hours or more is a continuous load. (per NEC)
 

charlie b

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augie47 said:
. . . that 60 watt lamp, once it is on for 3 hours or more is a continuous load. (per NEC)
I agree. But that does not change my answer to the original question. The notion of continuous loads does not enter into the calculation of loads associated with general purpose receptacles.

For that matter (and I might have missed something here), I believe that the concept of continuous loads is not addressed in 220. That is, we don't address continuous loads, as part of the process of performing service and feeder calculations. An extra 25% is included in the calculation of load for the largest motor, but that is not presented in terms of continuous operation of that motor.

The two points at which the notion of continuous loads is discussed are in connection with sizing the conductor and sizing the breaker, not in connection with calculating the load.
 

haskindm

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Location
Maryland
I guess what I should have said is that it doesn't matter if a load is continuous until the amperage load on a conductor is approaching the ampacity of the conductor. Figuring the 60-watt lamp at 125% still does not come anywhere close to loading the conductor to its maximum. It would only become an issue when I put close to 40 60-watt lamps on a 20-amp circuit and left them on continuously.
 

iwire

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Massachusetts
augie47 said:
howver, by definition, that 60 watt lamp, once it is on for 3 hours or more is a continuous load. (per NEC)

That particular lamp might be a continuous load but that will not make the circuit a continuous load unless that is the only lamp in the circuit.

Continuous Load. A load where the maximum current is expected to continue for 3 hours or more.

So if you have a circuit with ten 60 watt lamps and five of them stay on 24 hours a day the circuit is still not a continuous load until all the lamps are on for at least the same 3 hour period.
 

haskindm

Senior Member
Location
Maryland
iwire,
In your example the five lights that are on continuously (3-hours or more) would be calculated at 125% of their load. The five lights that are in use non-continuously would be calculated at 100%. The two values would be added together and compared to the ampacity of the circuit to determine if the circuit was adequate. In your example and assuming a 120-volt circuit:

60 watts at 120 volt = .5 amps

.5 amps X 5 lamps X 125% = 3.125 amps
.5 amps X 5 lamps = 2.5 amps
3.125 amps + 2.5 amps + 5.625 amps calculated load.
This would certainly be OK for either a 15 or 20 amp circuit.
 
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