need help with test question

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Random Rookie

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Illinois, USA
Hello Everyone!
I came across the test question regarding demand load calculation that I'm struggling to solve. Simply none of the answers fits my results. If someone can please explain me where is my mistake. Here is the question:
A two story dwelling has 9,375 sq/ft on each floor. Included in this living space is on the first floor 30' x 40' unfinished space ( not adapted for future use) and 13' 5" x 20' open porch. Calculate the general lighting, small appliance and laundry demand load. House has two kitchens, two laundry rooms and four bathrooms.
a) 22,677 VA standard calculation method
b) 23,412 VA standard calculation method
c) 59,220 VA standard calculation method
d) 63,750 VA standard calculation method

So here is how I'm doing it: 9,375 sq/ft x 2 floors = 18,750 sq/ft total
18,750 - (30'x 40' + 13'5" x 20") = 17,282 sq/ft living space
17,282 sq/ft x 3 VA = 51,847 VA General lighting
2 x laundry 1500 VA = 3000 VA
4 x small appliance (there are two kitchens) 1500 = 6000 VA
total: 60,847 VA
demand load = 10,000VA(100%of first 10,000VA) + 50,847 VA x 0,4 (40% of remaining) = 30,338.8KV

It doesn't fit any of the answers...
 
david luchini

david luchini

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Engineer
Random Rookie said:
Hello Everyone!
I came across the test question regarding demand load calculation that I'm struggling to solve. Simply none of the answers fits my results. If someone can please explain me where is my mistake. Here is the question:
A two story dwelling has 9,375 sq/ft on each floor. Included in this living space is on the first floor 30' x 40' unfinished space ( not adapted for future use) and 13' 5" x 20' open porch. Calculate the general lighting, small appliance and laundry demand load. House has two kitchens, two laundry rooms and four bathrooms.
a) 22,677 VA standard calculation method
b) 23,412 VA standard calculation method
c) 59,220 VA standard calculation method
d) 63,750 VA standard calculation method

So here is how I'm doing it: 9,375 sq/ft x 2 floors = 18,750 sq/ft total
18,750 - (30'x 40' + 13'5" x 20") = 17,282 sq/ft living space
17,282 sq/ft x 3 VA = 51,847 VA General lighting
2 x laundry 1500 VA = 3000 VA
4 x small appliance (there are two kitchens) 1500 = 6000 VA
total: 60,847 VA
demand load = 10,000VA(100%of first 10,000VA) + 50,847 VA x 0,4 (40% of remaining) = 30,338.8KV

It doesn't fit any of the answers...
Click to expand...

You used the Optional Calculation not the Standard Calculation. I don't get one of their answers exactly, but I get pretty close to one of them.
 
Last edited:
R

Random Rookie

Member
Location
Illinois, USA
Thank You for responding,
Honestly I would mark answer B, but that would be me guessing based on some calculations. I don't understand how it should look like in standard method, please explain.
 
M

Malywr

Senior Member
Location
New Jersey USA
Random Rookie said:
Hello Everyone!
I came across the test question regarding demand load calculation that I'm struggling to solve. Simply none of the answers fits my results. If someone can please explain me where is my mistake. Here is the question:
A two story dwelling has 9,375 sq/ft on each floor. Included in this living space is on the first floor 30' x 40' unfinished space ( not adapted for future use) and 13' 5" x 20' open porch. Calculate the general lighting, small appliance and laundry demand load. House has two kitchens, two laundry rooms and four bathrooms.
a) 22,677 VA standard calculation method
b) 23,412 VA standard calculation method
c) 59,220 VA standard calculation method
d) 63,750 VA standard calculation method

So here is how I'm doing it: 9,375 sq/ft x 2 floors = 18,750 sq/ft total
18,750 - (30'x 40' + 13'5" x 20") = 17,282 sq/ft living space
17,282 sq/ft x 3 VA = 51,847 VA General lighting
2 x laundry 1500 VA = 3000 VA
4 x small appliance (there are two kitchens) 1500 = 6000 VA
total: 60,847 VA
demand load = 10,000VA(100%of first 10,000VA) + 50,847 VA x 0,4 (40% of remaining) = 30,338.8KV

It doesn't fit any of the answers...
Click to expand...

I have 23,244VA so I got something wrong too.
Check 220.42 this is dwelling
Also example Annex D
 
Dennis Alwon

Dennis Alwon

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Location
Chapel Hill, NC
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Retired Electrical Contractor
Firstly, why would you give a question that was 3'5" x 20' instead of 3'6" x 20' That is unnecessary math..

Secondly I came up with 23,246 VA so I am not sure what the tester did. My guess is he did something with the sq.ft or did something with the bath receptacle?????
 
R

Random Rookie

Member
Location
Illinois, USA
Got it, thank You everyone!
23,244 VA is my result although I found it pretty bizarre that two methods of calculating the same thing leads to two different results off by ~7000VA, not mentioning that test answers are apparantly slightly off from the truth as well.
 
david luchini

david luchini

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Staff member
Location
Connecticut
Occupation
Engineer
Random Rookie said:
Got it, thank You everyone!
23,244 VA is my result although I found it pretty bizarre that two methods of calculating the same thing leads to two different results off by ~7000VA, not mentioning that test answers are apparantly slightly off from the truth as well.
Click to expand...

I would certainly expect different results from different methods. But the method you used doesn't apply to the load as you calculated it. That method applies to a single dwelling unit, and to the entire feeder/service load, not just a portion of it.
 
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