Optional method question

M

MLewis720

New User
Location
North Carolina
Occupation
Electrician
A single family dwelling is supplied with a 120/240 volt, single phase, three wire service. This dwelling has 2,240 square feet, a total appliance load of 18,500 VA, 10,000 VA of air conditioning, and 25,000 VA of electrical heating which is controlled by six thermostats. Using the optional method, what is the total computed load for this dwelling?
I get 27,888 but the answer key says it's 39,720. I did 2,240x3=6,720 for the square footage. 4,500 for small appl. 18,500 for nameplates. 6,720+4,500+18,500=29,720
First 10 kw at 100%=10,000. Remainder at 40%= 7,888. After demand factor I found the air conditioning and heat to both be 10,000.
10,000+7,888+10,000=27,888. What did I do wrong?
 
I think you are correct and the answer key is wrong. They missed the part about 40% after the first 10kVA of general load. Their answer is the general load without demand factor + 10kVA for the A/C or heat.
 
MLewis720 said:
A single family dwelling is supplied with a 120/240 volt, single phase, three wire service. This dwelling has 2,240 square feet, a total appliance load of 18,500 VA, 10,000 VA of air conditioning, and 25,000 VA of electrical heating which is controlled by six thermostats. Using the optional method, what is the total computed load for this dwelling?
I get 27,888 but the answer key says it's 39,720. I did 2,240x3=6,720 for the square footage. 4,500 for small appl. 18,500 for nameplates. 6,720+4,500+18,500=29,720
First 10 kw at 100%=10,000. Remainder at 40%= 7,888. After demand factor I found the air conditioning and heat to both be 10,000.
10,000+7,888+10,000=27,888. What did I do wrong?
Click to expand...
Just did this same question out the JCR test book, and yes the question asks “Using the optional method, what is the total computed load for this dwelling”

Glad you wrote this because I thought I was going crazy, The only way the answer key would be correct is if it read. “Using optional method, what is the total load BEFORE derations”

I also think there are some other mistakes in this JCR book as well as other ray holder & amazon books which makes the studying process much harder
 
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