Sizing a service load

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Bballfan1700

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Journeyman Electrician
Hey all, I'm having a bit of difficulty solving this question. As follows:

Using the standard method, calculate the service load for a 2,200 sq ft single family dwelling containing the following loads: range 14kW at 240, dryer 4.20 kW at 240V, dishwasher 1.20 kVA at 120V, waste disposer ¼ hp at 120V, water heater 4.20 kW, A/C two units 12A at 120V, electric heat 6 kW at 240V, and attic fan 1 ½ hp at 120V.

  • 142A
  • 133A
  • 160A
  • 130A
As many times as I've done it keep getting 119A, which isn't close to any of the answers above, not sure if I'm getting air conditioner and water heater flip flopped? I assumed I go based off the water heater 100% since there's one. Maybe it's something else I'm not getting? Thanks for your help in advance!
 
I get 141A...assume its 142 with rounding.

Don't forget the 75% four the 4 appliances as Dennis mentioned.
The range is 9.6kw.
The dryer is 5kw.
The heat is 6kw. (Larger than the AC)
The lighting, small appliance and laundry is 11.1kw total...3kw at 100% and 8.1kw at 35% (2.835kw.)

Total is 33.89kw, or 141A @ 240V
 
I think that the question askers forgot the 75% for the four appliances. I get 142A when you don't apply the 75% appliance demand factor.
 
Bballfan1700 said:
As many times as I've done it keep getting 119A, which isn't close to any of the answers above, not sure if I'm getting air conditioner and water heater flip flopped? I assumed I go based off the water heater 100% since there's one. Maybe it's something else I'm not getting? Thanks for your help in advance!
Click to expand...
Can you show your math, maybe we can spot the error if there is one.
 
david luchini said:
I think that the question askers forgot the 75% for the four appliances. I get 142A when you don't apply the 75% appliance demand factor.
Click to expand...


I don't know how you are getting that high. I found an error in mine as I used amps instead of VA but I still only get 28,935 or 121 amps

2835 Va for part 1
6300 Va for appliances- I used 600va for disp and 2400 for fan
5000 Va for Dryer
8800 Va for range
6000 va for heat

Total 28935 VA

What am I missing
 
2200 x 3 = 6600
3000va- SA (1200va dish) (696va waste) (4200 Water heater) (attic fan 2400va x1.25=3000va)
1500va- LA (1200va + 696va + 4200va +3000va) = 9096va x 0.75= 6822va
8800 range
6000 heat
6822va
+ 5000 dryer
= 37722va /240v = 157.175 (157amperes)
 
Dell3c said:
2200 x 3 = 6600
3000va- SA (1200va dish) (696va waste) (4200 Water heater) (attic fan 2400va x1.25=3000va)
1500va- LA (1200va + 696va + 4200va +3000va) = 9096va x 0.75= 6822va
8800 range
6000 heat
6822va
+ 5000 dryer
= 37722va /240v = 157.175 (157amperes)
Click to expand...


That is not correct. You have to take 6600 and add 3000 for small appliance branch circuit and 1500 for Laundry. Take the first 3000 at 100% and the rest at 35%. Then you add the rest-- appliances at 75%
 
Dennis Alwon said:
I don't know how you are getting that high. I found an error in mine as I used amps instead of VA but I still only get 28,935 or 121 amps

2835 Va for part 1
6300 Va for appliances- I used 600va for disp and 2400 for fan
5000 Va for Dryer
8800 Va for range
6000 va for heat

Total 28935 VA

What am I missing
Click to expand...
It should be 5835 for Part I.

And I'm not sure how you are getting 6300 for appliances.
 
Well I used 2400 for attic fan should be 3000 but that doesn't make much difference. I used 600 for disposal based on art 430.

1200 + 600 +4200+2400= 8,400 X 75% = 6300
 
2200 x 3 = 6600
6600 (1200va + 696va + 4200va + 2400va x 0.75)=6375va
3000 SA
1500 LA
=(11,100va)
-3000
= 8100
x 0.35
2835va
+3000
=5835va
(5835va +6375va +5000va +8800va + 6000va)=32010 /240v =133.375 (133 amperes)
 
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