commercial service calculations

[gras]

What size electric service is needed for a commercial office building if 4200 square feet, two 4.5kw water heaters, ten 1/4HP ceiling fans, 15kw heat, 7 1/2HP AC, 3kw sign, 3kw site lighting, 8kw of office equipment if single phase 120/240 volt? please show how you got your answer. Thank-you

 

[roger]

What size electric service is needed for a commercial office building if 4200 square feet, two 4.5kw water heaters, ten 1/4HP ceiling fans, 15kw heat, 7 1/2HP AC, 3kw sign, 3kw site lighting, 8kw of office equipment if single phase 120/240 volt? please show how you got your answer. Thank-you

Here's the way this works gras, (welcome to the forums) you have to try to do this yourself and show your steps of how you ended up with your answer, we will then confirm your answer or critique your work and help you get the correct answer .

Roger

 

[gras]

Commerical Service Calculations

Commerical Service Calculations

Thanks Rodger,
Here how I got my answer,
step #1 Table 220.12 4200 x 3.5 = 14,700
step # 2 Demand 100 %
step # 3 heat vrs ac heat larger 15,000
step # 4 outlets 8000
sign 3000
site lighting 3000
step # 5 Demand for outlets not over 10kva
step # 6 no kitchen
step # 7 largest moter 1/4 ceiling fan 5.8 x 125%= 7.25 x 120v = 870
9 other fans at 5.8x120v=696x9=6264
7134 total for fans
50,834 total load divided by 240 = 211.8 so a 225amp service?

 

[AllCircuitsElectrical]

2008 NEC back of book Annex D Examples >>D3

 

[augie47]

I believe you overlooked the 125% factor for the continuous load items. As noted in Post 4, Example D3 might help.

 

[gras]

commerical service calculations

commerical service calculations

Do I have to increase table 220.12 by 25% and also the sign and the site ligting by 25%

 

[augie47]

See if the * note at example D-3 helps.

 

[Smart $]

Also, your largest motor is likely included in your HVAC calculation at 125%. If it is, an additional extra 25% for the second largest motor is not required.