Water heater calc commercial setting

[comsparky]

Hey guys I have a situation where the customer has a small commercial office. There are 9 small sinks to wash hands that have little thankless 120v 1400w water heaters beneath each sink. The AHJ has failed the job because they are running off a 100 amp 3 phase service feeder. Now I know this doesn't fall under the dwelling demand factor, so are all 9 heaters to be calculated at 100 % ? I guess he is saying all 9 could run simultaneously and for long enough to create a problem. I gotta run them and see what the actual draw is, although I guess it's the nameplate that matters.
Thanks

 

[comsparky]

It looks like there are no demand factors for multiple water heaters in a commercial bldg, those only apply to dwelling units. It's 100% of nameplate unless it's a continuous load.

 

[HEYDOG]

If you have nine water heaters that are 120 bolts on a 3 phase 4 wire wye system. You can put 3 water heaters between L1 and neutral., 3 water heaters between L2 and the neutral, and 3 water heaters between L3 and the neutral. That would only be 4,200 watts per line or 35 amps per line. Not sure what else you might have being fed from same panel! Even at 1,25% it is 44 amps per line.

 

[comsparky]

I agree. The inspector seems to think that it needs a larger feed. There are other circuits obviously although they're all general use receptacles. I'll have to do a load calculation on everything and see what I come up with.