SFD calculation has me baffled

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stockhatch

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I have a sample question booklet with this question in it:

A single family dwelling has 3200 sq ft, and the following equipment:

15,000 VA fixed space heater at 240v
14,000 VA range at 240v
6,000 VA dryer at 240v
1,000 VA disposal at 120v
1,500 fan motor at 120v
Two, non-motor, 120v, non-fastened appliances with a total nameplate rating of 4,500 VA

Using the standard method of calcualtion, determine the dwellings total load.

I figured this:

3200 sq ft X 3 VA = 9600 VA
+ 4,500 VA for 2 small appliances and washer = 14,100 VA

3,000 VA at 100% = 3,000 VA

remaining 11,100 at 35% = 3,885 VA

total general of 6,885 VA

heat = 15,000 VA at 100% = 15,000 VA

appliances = 4,500 VA at 100% = 4,500 VA

add disposal at 100% 1,000 VA ?

add blower motor @ 100% VA = 1,500 VA ?

add dryer at 100% = 6,000 VA

add range at 8,800 VA (14,000 = 8,000 VA + .10% correction due to two points over 12KW rating)


TOTAL = 43,685 VA ?

The book answer is 43,935 VA and I cant figure out why. Is there something I am missing regarding the fan motor and disposal loads? Is it something else I am missing, or is the book wrong?

Thanks in advance.
 
ASK_EDDIE

ASK_EDDIE

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220.18 A , The Largest Motor Load Is Taken At 125% , However Your Difference Is 250va It Appears That The Load Of The Disposal Was Taken Instead Of Blower Moter
 
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stockhatch

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I guess the blower motor was no longer considered the largest motor load due to it being for the AC and omitted due to the heat being used in the calculation...(Wow, what a terrible sentence that was) This was kinda a sketchy question. I hope they arent all like that.
 
ASK_EDDIE

ASK_EDDIE

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I bought quite a few study aids over the years, they're not always correct.. i've found out when you start finding mistakes on study aids you are ready to take your test.
 
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stockhatch

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LOL. Thanks. I know Im not at that point yet. I am taking the exam Sat. but I doubt Ill pass it. I just havent studied like I should. At the very least it will give me some exposure, and give me an idea of my weakest areas.
 
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