NEC 220.84 Calculation with Electric Range

[wowsk]

I have a 4 unit town house that I used 220.84 to calculate the load for the entire building. The stove that is to be used is 15KW at 240V. This is the sum of all 4 burners, oven element, and broiler element.

Am I allowed to use 220.55 to get by using a maximum demand of 8kW+((15kW-12kW) * 5%) = 8.15kW?

It just doesn't make sense to me to use 15kW for the calculation as no one is going to have all elements running full steam.

Or is it assumed the 45% demand factor I can apply from 220.84 accounts for this?

Thanks

 

[wwhitney]

I have a 4 unit town house that I used 220.84 to calculate the load for the entire building. The stove that is to be used is 15KW at 240V. This is the sum of all 4 burners, oven element, and broiler element.

Am I allowed to use 220.55 to get by using a maximum demand

No, for a 220.84 calculation, nothing in Article 220 Part III applies, including Table 220.55. 220.84(C)(3) says to use the nameplate rating of the range. Then you get to apply a 45% demand factor at the end.

of 8kW+((15kW-12kW) * 5%) = 8.15kW?

The above calculation is incorrect, 220.55 would be 8 kW * (1 + ceiling (15-12) * 0.05) = 8 * 1.15 = 9.2 kW for one range, or 17 kW * 1.15 = 19.6 kW for 4 ranges.

Cheers, Wayne

 

[wowsk]

Thanks Wayne, appreciate the help.

 

[Dennis Alwon]

No, for a 220.84 calculation, nothing in Article 220 Part III applies, including Table 220.55. 220.84(C)(3) says to use the nameplate rating of the range. Then you get to apply a 45% demand factor at the end.



The above calculation is incorrect, 220.55 would be 8 kW * (1 + ceiling (15-12) * 0.05) = 8 * 1.15 = 9.2 kW for one range, or 17 kW * 1.15 = 19.6 kW for 4 ranges.

Cheers, Wayne

Shouldn't that be 17kw * 1.25= 21.25

 

[wwhitney]

Shouldn't that be 17kw * 1.25= 21.25

Determining the multiplier for identical ranges over 12 kW is based on the rating of a single range, not the value from Table 220.55. So for (4) 15 kW ranges, the multiplier is 1.15, and the table value is 17 kW, so the answer is 17 * 1.15.

Cheers, Wayne

 

[Dennis Alwon]

Determining the multiplier for identical ranges over 12 kW is based on the rating of a single range, not the value from Table 220.55. So for (4) 15 kW ranges, the multiplier is 1.15, and the table value is 17 kW, so the answer is 17 * 1.15.

Cheers, Wayne

Sorry I was thinking 17kw range---duh...