Load calculation

[wc86]

Would a 3 unit multifamily with window mounted plug-in air conditioners and baseboard heat tied to gas water heaters(not house load) qualify for using the 220.84 optional method? If so how would the calculation work if there were multiple a/c units in each apartment in different quantities?

 

[tortuga]

Would a 3 unit multifamily with window mounted plug-in air conditioners and baseboard heat tied to gas water heaters(not house load) qualify for using the 220.84 optional method? If so how would the calculation work if there were multiple a/c units in each apartment in different quantities?

For the service or feeder load of all 3?
Whats the total square feet of all units?
What are the nameplate ratings of all the appliances fastened in place ?
Whats the larger load heating or AC?

 

[wwhitney]

Would a 3 unit multifamily with window mounted plug-in air conditioners and baseboard heat tied to gas water heaters(not house load) qualify for using the 220.84 optional method?

220.84(A)(3) requires each unit to be "equipped" with electric space heating or air conditioning. Sounds like that would qualify, although I imagine the details might be subject to further scrutiny.

If so how would the calculation work if there were multiple a/c units in each apartment in different quantities?

220.84 just totals the connected load for the units (excluding house loads, calculated separately) and applies a demand factor. The exception is that you only need to use the larger of the air conditioning and heating loads, but in your example you don't have any heating load. So you'd add up all the air conditioning loads for your total connected load.

Cheers, Wayne

 

[tortuga]

Note that 220.84 is just for the service or feeder that supplies all the units. Then you use the 220.82 optional calc for each dwelling unit feeder.