Determine the feeder capacity fastened-in-place appliance load in a dwelling unit

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ones_zeros

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Hello,
I was trying to figure out this calculation to make sure I fully understand its steps to get the correct answer
Here is the question

Calculation Example
Determine the feeder capacity needed for a 120/240-volt fastened-in-place appliance load in a dwelling unit for the following:

Appliance Rating Load
Water heater 4000 W, 240 V 4000 VA
Kitchen disposal 1/2 hp, 120 V 1176 VA
Dishwasher 1200 W, 120 V 1200 VA
Furnace motor 1/4 hp, 120 V 696 VA
Attic fan 1/4 hp, 120 V 696 VA
Water pump 1/2 hp, 240 V 1176 VA


STEP 1.
Calculate the total of the six fastened-in-place appliances:

Total load = 4000VA + 1176 Va + 1200 VA +696 VA + 696 VA + 1176 VA =8944 VA

STEP 2.
Because the load is for more than four appliances, apply a demand factor of 75 percent:

8944 VA X 0.75 = 6708 VA

When the question asks
Determine the feeder capacity needed for a 120/240-volt fastened-in-place appliance load in a dwelling unit
Click to expand...
Is 6708 VA the answer there looking for?

Thanks for helping
 
IMO, you would need to add 294 va to your 8944 va for 25% of the largest motor
 
OK, so your saying take the
8944 VA +294 VA = 9238 VA

then take 9238 VA X 0.75 =6928.5 VA (would this be the final answer?)


thanks
 
can you guys verify for me that my final answer is correct?

Calculation Example
Determine the feeder capacity needed for a 120/240-volt fastened-in-place appliance load in a dwelling unit for the following:

Appliance Rating Load
Water heater 4000 W, 240 V 4000 VA
Kitchen disposal 1/2 hp, 120 V 1176 VA
Dishwasher 1200 W, 120 V 1200 VA
Furnace motor 1/4 hp, 120 V 696 VA
Attic fan 1/4 hp, 120 V 696 VA
Water pump 1/2 hp, 240 V 1176 VA


STEP 1.
Calculate the total of the six fastened-in-place appliances:

Total load = 4000VA + 1176 Va + 1200 VA +696 VA + 696 VA + 1176 VA =8944 VA

STEP 2.
Because the load is for more than four appliances, apply a demand factor of 75 percent:

8944 VA X 0.75 = 6708 VA

When the question asks
Determine the feeder capacity needed for a 120/240-volt fastened-in-place appliance load in a dwelling unit


Is 6708 VA the answer there looking for?


25% of the largest motor8944 VA +294 VA = 9238 VA

then take 9238 VA X 0.75 =6928.5 VA (would this be the final answer?)
Click to expand...


thanks for helping
 
I would not consider the attic fan, furnace blower nor the water pump as an appliance. The code is not perfect on this issue but that is my opinion.

220.53 says nothing about 125% for motors.... This question is not clear. Are they saying all those items are appliances or are they asking you to determine which are appliances and calculate the load on those items?
 
Dennis: I fear all we will get is opinions but as far as the 25%, I added it since 220.50 references 430.24 where they add the 25% and also in Annex D, Example D3a adds the 25% fro that feeder calculation. Not saying I'm necessarily correct just justifying.
 
Since the op was using 75% I believe we are using the standard calculation. D(3)(a) is for industrial feeders.
 
Well that is taking 25% of the largest motor which happens to be an a/c unit. An a/c unit is not an appliance. I can tell you that on mike holt spreadsheet he does not take 25% of appliance motor. Either 100% or 75% if there are 4 or more. My opinion is you don't need 125% but I am often wrong on these calcs
 
Dennis Alwon said:
but I am often wrong on these calcs
Click to expand...

As I suspect many of us are. :D

Here is what I see as kind of funny, when we take a test on this it matters. We get all stressed one way or the other trying to reach the same answer as the creator of the test.

However, in real life none of it matters that much, 25% more or less on one specific item is not going to result in a safety or usability issue. The article 220 calculation are so conservative you would really have to screw up badly to end up with an unsafe installation.


(Notice how I did not say if I see it like Dennis or Gus, when I do calculations I use the examples in the back and hope for the best. :p)
 
That's a cop out...:D But you are correct. I hardly ever do a dwelling calculation and 25% of a motor in a dwelling will not mean anything at all. I can't understand why the standard calculation usually will return a number 40-50 amps higher than the optional calculation
 
Thanks guys for all your help & time
i agree this question is very vague

I have to ask...
if you guys had to answer this question on a test
how would you answer it?

Thanks again!
 
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