Example No. D6 Maximum Demand for Range Loads
Table 220.55, Column C, applies to ranges not over 12 kW. The application of Note 1 to ranges over 12 kW (and not over 27 kW) and Note 2 to ranges over 8 3/4 kW (and not over 27 kW) is illustrated in the following two examples:
A. Ranges all the same rating (See Table 220.55, Note 1)
Assume 24 ranges each rated 16 kW. From Table 220.55, Column C the maximum demand for 24 ranges of 12 kW rating is 39 kW.
16 kW exeeeds 12 kW by 4
5% x 4 = 20% (5% increase for each kW in excess of 12)
39 kW x 20% = 7.8 kW increase
39 kW + 7.8 kW = 46.8 kW (value to be used in selection of feeders)
B. Ranges of unequal rating (See Table 220.55, Note 2)
Assume:
5 ranges each rated 11 kW
2 ranges each rated 12 kW
20 ranges each rated 13.5 kW
3 ranges each rated 18 kW
5 x 12 |
= 60 kW (Use 12 kW for range rated less than 12) |
2 x 12 |
= 24 kW |
20 x 13.5 |
= 270 kW |
3 x 18 |
= 54 kW |
30 ranges |
408 kW total kW |
408 kW ÷ 30 ranges = 13.6 kW (average to be used for calculation)
From Table 220.55, Column C, the demand for 30 ranges of 12 kW rating is 15 kW + (1 kW x 30 ranges) = 45 kW.
13.6 exceeds 12 by 1.6 (use 2 kW)
5% x 2 = 10% (5% increase for each kW in excess of 12 kW)
45 kW x 10% = 4.5 kW increase
45 kW + 4.5 kW = 49.5 kw: (value to be used in selection of feeders)