# What is the demand load for these ranges?

• posted

Ranges of unequal rating supplied by 3-phase 208Y/120 volt circuit. Used for instructional purpose or for multiple dwelling units. What is the demand load for the service or a feeder?

6 ranges at 3 KW 10 ovens at 5 KW 14 ranges at 6 KW 45 ranges at 12 KW 25 ranges at 15 KW 1 3-phase range at 20 KW
• posted

I come up with this: Ranges of unequal rating supplied by 3-phase 208Y/120 volt circuit.

6 ranges at 3 KW 10 ovens at 5 KW 14 ranges at 6 KW 45 ranges at 12 KW 25 ranges at 15 KW 1 3-phase range at 20 KW

This problem does not fit nicely within the rules of Section 220.55 or Table

220.55 and accompanying Notes.

Divide ranges to balance load and find how many are on each two phases.

For the 3-phase range divide load by three and apply to each phase.

Phases AB AC BC 2 - 3 KW 2 - 3 KW 2 - 3 KW 4 - 5 KW 3 - 5 KW 3 - 5 KW 5 - 6 KW 5 - 6 KW 4 - 6 KW 15 - 12 KW 15 - 12 KW 15 - 12 KW 8 - 15 KW 8 - 15 KW 9 - 15 KW 1 - 7 KW 1 - 7 KW 1 - 6 KW _________________________________________ 35 - 366 KW 34 - 363 KW 34 - 359 KW

Select phases with maximum number of ranges which is AB.

2 x number of ranges/phase = 2 x 35 = 70

Double the number of ranges for each category and use 8.8 KW for any value below 8 3/4 KW.

Using 24 - 8.8 KW, 30 - 12 KW, and 16 - 15 KW use section 3 to find demand.

Demand is 81.38 KW using Section 3.

81.38 KW /2 = 40.69 KW

The total demand load is 3 x 40.7 = 122.1 KW

The line current is:

I = 122,100 / (1.732 x 208) = 122,100 / 360.3 = 339 amperes

I used my calculator at: