Dryers in a Multifamily dwelling

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aelectricalman

aelectricalman

Senior Member
Location
KY
I hope me asking these question is not bothering anyone! If so, just tell me and I will quit.

Here is my question: A multifamily dwelling (40 units) contains a 4.50KW electric Clothes dryer each. What is the feeder and service calculated load for all the dryers?

I went to Table 220.84 ( optional calc) and used 28% D.F. and got 50.4 KW. I also went to Table 220.54 and did the math (35 - [.5 x (number of dryers 40- 23)] = 26.5KW

My choices are

27KW
53KW
60KW
90KW

I feel like i cant round that 26.5 KW up to 27KW. I was told while in Engineering not to round up when sizing feeders! My obvious first choice is 26.5 but im not confident with that answer. Any thoughts.
 
Chris,

Are you sure you wern't told not to round down ? Rounding up can only make it safer, yet

more costly, rounding down will give you a smaller size .(feeder/service). That's my

thought !!
 
Couple of things real quick, T-220.84 can't be used for just dryers. It can only be used if

the entire complex is on one service and it is used for the load of all units combined.

Also, I'll do the math agian, but, I got 57.6kw using T-220.54
 
Here we go

Here we go

OK guys, big breath......
220.54 says 5000 watts or nameplate, whichever is larger...

The math
40 X 5 kw = 200 kw

Table 220.54

40 dryers would be 35% - .5% for each dryer exceeding 23

17 X .5% = 8.5%
35% - 8.5% = 26.5%
200 kw X .265 = 53 kw

Please check me, thank you.
:D
 
Sorry was writing so fast I missed a number, and symbol
40(5kva)=200000(26.5% or .265)=53Kva

The bold is what I missed above;)
 
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