NEC 2008
Section 220.14 (A) and (I)
Suppose: A receptacle outlet is installed, so that a copy machine can be installed with a wattage of 1500. The copy machine is connected via an attachment plug to a receptacle.
How would you consider this, when determining the feeder/service demand load.
220.14 Subsection "A" specifically discusses appliances and a copy machine in my opinion is an appliance. If using subsection "A", then the demand load would be 1500 watts.
220.14 Subsection "I" specifically discusses receptacle outlets and this scenario does represent a receptacle outlet. The receptacle outlet must be calculated at not less than 180 watts. In this case, the receptacle could be counted at the 1500 watts.
Suppose you have 10 of these copy machines.
If you calculate them using subsection A, you end up with a demand load of 10 x 1500 @ 100% = 15,000 VA
If you calculate them using subsection I, you end up with a demand load of 10 x 1500 with the first 10k @ 100% and the remaining at 50% (10,000 @ 100% + 5,000 @ 50%) giving a total demand load of 12,500 VA
In this example the difference in demand is insignificant. However, in a big institutional building such as a school, university etc, the difference in demand at the point of the service can vary significantly. Which calculation method do you think is more appropriate?
Section 220.14 (A) and (I)
Suppose: A receptacle outlet is installed, so that a copy machine can be installed with a wattage of 1500. The copy machine is connected via an attachment plug to a receptacle.
How would you consider this, when determining the feeder/service demand load.
220.14 Subsection "A" specifically discusses appliances and a copy machine in my opinion is an appliance. If using subsection "A", then the demand load would be 1500 watts.
220.14 Subsection "I" specifically discusses receptacle outlets and this scenario does represent a receptacle outlet. The receptacle outlet must be calculated at not less than 180 watts. In this case, the receptacle could be counted at the 1500 watts.
Suppose you have 10 of these copy machines.
If you calculate them using subsection A, you end up with a demand load of 10 x 1500 @ 100% = 15,000 VA
If you calculate them using subsection I, you end up with a demand load of 10 x 1500 with the first 10k @ 100% and the remaining at 50% (10,000 @ 100% + 5,000 @ 50%) giving a total demand load of 12,500 VA
In this example the difference in demand is insignificant. However, in a big institutional building such as a school, university etc, the difference in demand at the point of the service can vary significantly. Which calculation method do you think is more appropriate?