Calculate how many lighting circuits

[Bishop__8128]

When calculating how many lighting branch circuits you may need in a dwelling I was told you can use the numbers 600 for 15 amps and 800 for 20amp, and divide that into the square footage of the home. My question is, is that correct and would you round up or round down?

Ex:
1250sqft. ÷ 800= 1.5625 round up to get 2 branch circuits. Correct?

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[Greg1707]

3 volt amps per square foot

3 volt amps per square foot

I just use three volt amps per square foot and multiply times the number of square feet. This is for lighting and general receptacle load.
Having a fixed number as you suggest is not useful since there is no way to anticipate the type of bulbs etc. LED vs incandescent.

 

[luckylerado]

1250sqft * 3va/sqft = 3750 va Minimum lighting load required per 220.12

3750va/120v=31.25A=3 15A circuits or 2 20A circuits

220.12 Informational Note: The unit values herein are based on
minimum load conditions and 100 percent power factor
and may not provide sufficient capacity for the installation
contemplated.

 

[Smart $]

When calculating how many lighting branch circuits you may need in a dwelling I was told you can use the numbers 600 for 15 amps and 800 for 20amp, and divide that into the square footage of the home. My question is, is that correct and would you round up or round down?

Ex:
1250sqft. ÷ 800= 1.5625 round up to get 2 branch circuits. Correct?

Sent from my SM-N900T using Tapatalk

120V 20A) 1250sqft × 3VA/sqft ÷ 120V ÷ 16A = 1.95.... round up to 2

120V 15A) 1250sqft × 3VA/sqft ÷ 120V ÷ 12A = 2.60... round up to 3

120V 20A equivalent) 1250sqft ÷ 640

120V 15A equivalent) 1250sqft ÷ 480