Multifamily Laundry Room Elec Dryer Demand

[phbui]

If I am calculating the load for a multifamily building with 100+ dwelling units using optional method and there is a shared laundry room that has 17 washer/dryers fed from house panel, would the dryers be calculated at 100%?

 

[david luchini]

Yes

 

[Fred B]

In order to use the optional method you must meet all the requirements of 220.84 and then would use the name plate rating of the dryers.
Otherwise would use the larger of 5000W or name plate rating and apply 220.54 for demand factor for getting total load to be applied. Table shows this for your 17 dryers.

12–23

47% minus 1% for each dryer exceeding 11

Also add in 220.52(B) Laundry Circuit Load.
A load of not less than 1500 volt-amperes shall be included for each 2-wire laundry branch circuit installed as covered by 210.11(C)(2). This load shall be permitted to be included with the general lighting load and shall be subjected to the demand factors provided in Table 220.42.

 

[wwhitney]

220.84(B) specifies that house loads be calculated separately under Part III.

220.54, which is part of Part III, refers to clothes dryer(s) in a dwelling unit(s). That means Table 220.54 demand factors would not apply to clothes dryers in a common laundry room. Table 220.54 is for the situation of a service or feeder supplying multiple units, where each clothes dryer is within an individual unit.

Which makes sense--with a common laundry room with 17 dryers shared by 100+ dwelling units, the utilization factor for each dryer is going to be much higher than if you had 100+ dryers, one in each dwelling unit.

Cheers, Wayne