Robert Zan
Member
If a building has 40 apartment units and if you want to add 5Kw dryer to each unit, how will you calculate the additional Amps increase on the feeder (240V, single phase) power supply? The choices given are maximum 300 Amps.
adding dryers... 40 of them
- Thread starter Robert Zan
- Start date
- Status
- Location
- Massachusetts
You would do an entire load calculation following the rules in Article 220.
FrancisDoody
Senior Member
- Location
- Durham, CT
Dryer Calculations
Dryer Calculations
24-42 dryers
To find the percentage of the demand factor that would be applied to the full load of 40 dryers you would use this formula from Table 220.54
%=35-[0.5 x (40-23)]
%=35-[0.5 x (40-23=17)]
%=35-[0.5 x 17]
%=35-[8.5]
%=35-8.5
%=26.5
40 Dryers at 5000 VA=200,000 total VA
200,000 X 26.5%=53000 VA
53,000/240v=221 A
The additional load would be 221 amps
Dryer Calculations
24-42 dryers
To find the percentage of the demand factor that would be applied to the full load of 40 dryers you would use this formula from Table 220.54
%=35-[0.5 x (40-23)]
%=35-[0.5 x (40-23=17)]
%=35-[0.5 x 17]
%=35-[8.5]
%=35-8.5
%=26.5
40 Dryers at 5000 VA=200,000 total VA
200,000 X 26.5%=53000 VA
53,000/240v=221 A
The additional load would be 221 amps
- Status