NEC 220.53 - 75% demand to 4 central water heaters

[designer82]

Working on a 14 unit multi-family residential project, which will have central hot water via four 4.5kw (each) heat pump water heaters.

These water heaters will be located in a community mechanical space in the basement.

Question is, can I apply the 75% demand factor allowed by 220.53 to these heat pump water heaters?

It does say:
It shall be permissible to apply a demand factor of 75 percent to the nameplate rating load of four or more appliances rated 1∕ 4 hp or greater, or 500 watts or greater, that are fastened in place, and that are served by the same feeder or service in a one-family, two-family, or multifamily dwelling

My service calc. is ultra close and the 75% demand would actually make big difference if I can use it.(new transformer vs. no new transformer needed)\

I don't see why not personally. Would appreciate your thoughts. Thanks

 

[JoeStillman]

If the water heaters were located in four of the 14 units there would be no question that you can take the 75% diversity. I would use the 75% factor in the overall service calc, but not in the house panel feeder sizing calc.