Lighting demand load

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bgolpmp

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Hello and thanks for reading.

I am studying for my Masters and have a question.
I took a class to help me prepair for the test and am doing a test over and am getting a diffrend answer than the instructor had.

Q.

Calculate the lighting demand for a store with 5,000 sq ft on the 1st floor and 6,000 sq ft on the 2nd floor, the building is slab on grade and the system operates at 120/s08 volts 3 phase 4 wires.

a) 65 amps
b) 85.3 amps
c) 91.7 amps
d) 100 amps

He says the answer is c 91.7 amps and the only way I get that answer is if I don't add the 125% for continous load for a store.

How is the correct way to figure this one out?

Thanks
Andy
 
Read 220.42 and take a look at Table 220.42. This is the "Demand Load" for the lighting part of the service calcs.
 
Dave

Thanks for the reply.

I looked at T220.42 and it says 100% but in mike holts examples he calculates it based on continuous load and multiplies by 125%?????

I am not sure if you have his book
"Electrical NEC Exam Preperation" for the 2005 code.
On page 463 figure 11-14 he states " store lighting is continuous load at 125%"

Thanks
Andy
 
Sorry....don't have Mike's Book. Mike might be calculating a feeder rather than the service calcs....does he reference 215.2?
 
It looks like he is using Table 220.12 for the calculation. Since you do not have a connected load.

You have a total of 11,000 sq.ft. and the table shows the unit load for a store is 3va/sq.ft.

So 11,000sq.ft. x 3va/sq.ft = 33,000 VA

33,000VA / (208V x 1.732) = 91.7A

Hope this helps.
 
I did the load calculation. The demand load shall be 91.7Ax125%. The lighting load in store is definitely counted as continuous load. You can ask the instructor why he came up the different answer.
 
dahualin said:
I did the load calculation. The demand load shall be 91.7Ax125%. The lighting load in store is definitely counted as continuous load. You can ask the instructor why he came up the different answer.
Click to expand...

Ah yes it is supposed to include the 125%, sorry had a brain fart and was thinking of finding the connected load towards the end of my thought process. He might have made the same mistake as I did thinking he wanted to find the connected and not the demand.
 
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