Electric Range Load in 220.42 vs 220.84

[KBot9]

I have an existing multifamily, say 100 units, that wants to upgrade each panel and run electric ranges to eliminate gas. The Service is 3 phase. The Ranges are single phase three wire 220, 8000kW.

220.55 says that "where 2 or more single phase are supplied by a three phase ...service...." the calc would look like this (as shown in the Annex D5(A):

Max rages btwn any 2 phases (34) times 2 (68) then use 68 "ranges" in Table 220.55 Column "B" (cause under 8750 watts) for the "61 & Over" Line so: 25,000W & (68 *.75kW =) 51000W for 76,000W, divided by 2 for Single Phase Load (38000W) then times 3 for three phase = Total Electric Range Load on the 3 Phase Service Feeder of 114kW divided by 360 = 316.6 Amps

In the Multifamily Load Cal Option 220.84 though is says Add Electric Nameplate to total (of Gen Lighting & Small Appliances & Fixed Appliances) then use table for over 62 units and multiply by 23%. In this case 8000W * 100 Units = 800,000 *.23 = 184,000W Divided by 360 = 511.1 Amps

Big Difference for the exact same Line Item.

Since in the 220.84 method the Ranges are the same exact ranges and *If they dont exist yet the calc can be the Gen/Appliance loads times 23% then a year from now they add electric ranges and THEN I can use 220.55?

I dont understand if 220.55 trumps 220.84 now, and I can still use the Single to Three Phase electric range calc... or if 220.84 must have the full nameplate. When I can just as easily merely calculate the Service Feeder Load based on 220.84 for everything but the ranges then say Im adding the ranges later for 316 amps and "luckily" I already sized the Service Feeders for those 316 additional amps coming.

 

[wwhitney]

I only skimmed most of your post, but my comment is that 220.84's first sentence refers to doing a calculation "in accordance with Table 220.84 instead of Part III of this article".

That means whenever you are using Table 220.84 in your calculation, you are to ignore all of Article 220 Part III, which includes 220.55.

So you can do two different calculations with entirely separate methods (same input data), one using Article 220 Part III, and one using 220.84. Whichever value is less controls.

Cheers, Wayne

 

[KBot9]

Thanks Wayne. I guess that is the answer. I also answered partially myself re-reading that I cannot Do 220.84 without the Ranges then add them later since one of the very conditions to employ .84 is that ranges are included, so that settles everything, thanks.