Studying for exam

[Worlds Gr8est Electrician]

I am going to be going for my limited license in the beginning of July. I took a 6 month exam prep course at a local community college and am now studying the material from the course until the day I take my exam. I just want to see what everyone else comes up with for this calculation. Here it is.

1500sq ft single family dwelling
Kitchen X2
laundry
2- 4kw wall mounted oven
1- 5.1kw counter mounted cooking unit
water heater 4.5kw
dishwasher 1200kw
washer dryer combo 5000kw

6- 7amp 240v ac units
1.5 kw bathroom space heater



Here is what I got

1500 x 3va = 4500
Kit x2 3000
laundry 1500
2 wall mounted ovens 4kw X 2 X 65% = 5200 Table 220.55
counter mounted cooking unit 5100kw X 80% = 4080 Table 220.55
water heater 4500
dishwasher 1200
washer dryer combo 5000
______________
28980
- 10000
___________
18,980 x 40%= 7,592

AC- 240 X 7amp= 1680kw X 6 = 10080

Space heater 1500kw X 65% = 975

10,000
7,592
10080
_______
27,672kw



So am I correct? Hopefully what I typed is easy to follow.

 

[david luchini]

It appears that you are using the Optional Method for Dwelling Units per 220.82.

If that is the case, I would suggest that your wall ovens and cooking units should be included at 100% in the first part of your equation, rather than applying the demand factors of 220.55.

See 220.82(B)(3).

 

[Worlds Gr8est Electrician]

Well that was my main question. Do I figure the ovens and cooking unit at 100% or apply the demand factor. Could you tell me why I shouldn't apply the demand factor. Also I wasn't 100% on whether I had the ac units figured right or not. Thanks for the help.

 

[Worlds Gr8est Electrician]

Sorry missed where you said to look at 220.82 b 3

So it says 100% of first 10 kva plays 40% of remainder. So are You saying I should total up The KVA for my to ovens and counter mounted cooking unit and figure the first 10 kva at 100% and then the remainder at 40% if so then could you tell me when I would use table 220.55 thank you

 

[david luchini]

Sorry missed where you said to look at 220.82 b 3

So it says 100% of first 10 kva plays 40% of remainder. So are You saying I should total up The KVA for my to ovens and counter mounted cooking unit and figure the first 10 kva at 100% and then the remainder at 40% if so then could you tell me when I would use table 220.55 thank you

Yes, using the optional method, add up 3va/sf of lighting, 1500va for each SA and laundry circuit, and the nameplate of appliances, ranges, ovens, cooking units, clothes dryers, permanently connected motors, etc (per 220.82(B)) and to 100% of the first 10kVA plus 40% of the remainder. Then add the heating or cooling as listed in 220.82(C). It appears to me that you figured that part correctly.

You would use T220.55 if you were calculating the feeder or service load using the method described in 220.40 rather than using the optional method.

 

[Worlds Gr8est Electrician]

Ok I am following now. The way i was figuring in the cooking appliances is for the standard method. So like you said I just figure them in at nameplate rating and add that in with the other loads and then continue on with my optional method calculation.

Thanks for the help.

This is what it should have looked like

1500 x 3va = 4500
Kit x2 3000
laundry 1500
two 4kw wall mounted ovens
one 5.1kw counter mounted cooking unit
water heater 4500
dishwasher 1200
washer dryer combo 5000
______________
32800
- 10000
___________
22800 x 40%= 9120kw

AC- 240 X 7amp= 1680kw X 6 = 10080

Space heater 1500kw X 65% = 975

10,000
9120
10080
_______
29200kw