Using the Optional Calculation Method

[Angel Electric]

Using the optional calculation method, what is the calculated load for a service serving a single family dwelling when given the following information.

The dwelling has 1200 Sq. Ft. and the following electrical appliances that are fastened in place!

1-240 Volt 10 KVA range
1-240 volt 4800 Va clothes dryer
1-disposal 750 VA
The air conditioning is rated at 5000 VA and the baseboard heating, which is controlled by six separate thermostats is rated at 10000 VA.

I have followed my study manual and got. 19740 VA

The answer provided is 20460 VA.

I have worked this several times and I am not getting the same answer as the one provided. It is really making me second guess all I have learned regarding residential load calculations.

 

[wirebender]

I get 20460 with the info provided. See 220.82(B) and (C)
Maybe you should show your calculations.

Also, why no water heater?

 

[Angel Electric]

Calculations

Calculations

1200 sq. Ft. x 3 = 3600 VA.
Small App. x 2 = 3000 VA.
Laundry = 1500 VA.
Range = 8000 VA.
Dryer = 5000 VA.
Disposal = 750 VA.
______________+____________
21250 VA -10000=11250 X .40= 4500 VA.

10000
+ 4500 Derated Calculation
------------------------

Add The Ac + 5000
--------------------
19500 VA.

Thanks In Advance!!

 

[Angel Electric]

Could you show me the calculations for this answer? I think it will clear up.

Could you show me the calculations for this answer? I think it will clear up.

The test booklet I'm using does not show how they worked out the answers. Could you please share the worked out problem. I want to follow on this one..

 

[Dennis Alwon]

I get 20,460

 

[Dennis Alwon]

1200 sq. ft x 3 = 3600
Laundry 1500
2 Kit Cir. 3000
Dryer 4800
Range 10000
Disposal 750

total 23650



first 10,000 at 100% 10000
Next at 40% 13650 * 40% = 5460


10000+5460= 15460
A/c is largest load @ 5000

15460 + 5000 = 20460

 

[Dennis Alwon]

You have 8kw for the range instead of 10,000
and the dryer should be 4800 not 5000-- 8kw for range & 5000 for dryer is for non optional calc

 

[Dennis Alwon]

Check your addition on the calc. your 21 2150 is not correctly added. At that point you should have 21850 and then correct for the range and dryer 21850+2000 (range addition)-200(dryer deduct)=23650

 

[Angel Electric]

Big 10-4

Thanks for the assist... I dont care what the other teaching authorities say about this site... You guys have been there for the Industry in an awesome way for respectable profit...
Thanks...
I'm taking my contractors test for NC. Soon. I keep getting 72-75 on practice test... I wont be going to take it until I get a 85 or better.. I could not get there without this site...

I see I added incorrectly as well as derated the range and uprated the dryer unnecessarily.

 

[Dennis Alwon]

Big 10-4

Thanks for the assist... I dont care what the other teaching authorities say about this site... You guys have been there for the Industry in an awesome way for respectable profit...
Thanks...
I'm taking my contractors test for NC. Soon. I keep getting 72-75 on practice test... I wont be going to take it until I get a 85 or better.. I could not get there without this site...

Good luck-- and thanks for the compliments... You live year round at the outer banks?

 

[Angel Electric]

Yes, It is a neat place...

 

[Dennis Alwon]

I have not been there in many many years-- used to do alot of bird watching on the outer banks. It is a nice area