General Lighting Load Calculations

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McKinney

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13700 sh 13700 tyler tx
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Service manager
Regarding general lighting load calculations , when is it required to apply 125% ?

Non Dwelling Example : 12,000sqft x 3.5 = 42k **** 120x20amp = 2400 = 42k dived by 2400= 17.5

Thank You,
 
I should say I have never seen a calculation that required 125% for lighting in a residence. The 3 watts/ft sq. takes all that into account.
 
Here is what the 2020 states

(J) Dwelling Units.


In one-family, two-family, and multifamily dwellings, the minimum unit load shall be not less than 33 volt-amperes/m2 (3 volt-amperes/ft2). The lighting and receptacle outlets specified in 220.14(J)(1), (J)(2), and (J)(3) are included in the minimum unit load. No additional load calculations shall be required for such outlets. The minimum lighting load shall be determined using the minimum unit load and the floor area as determined in 220.11 for dwelling occupancies. Motors rated less than 1⁄8 hp and connected to a lighting circuit shall be considered part of the minimum lighting load.
  • (1)
    All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in 210.11(C)(3) and 210.11(C)(4)
  • (2)
    The receptacle outlets specified in 210.52(E) and (G)
  • (3)
    The lighting outlets specified in 210.70
Click to expand...
 
McKinney said:
Regarding general lighting load calculations , when is it required to apply 125% ?

Non Dwelling Example : 12,000sqft x 3.5 = 42k **** 120x20amp = 2400 = 42k dived by 2400= 17.5

Thank You,
Click to expand...
The 125% comes into play when sizing conductors for a feeder 215.2(A)(1)(a), or for branch circuit wiring with continuous loads per 210.19(A)(1)(a).
Lighting can be a continuous load in non dwelling occupancies, a lot of times it is more likely a combination of continuous and non-continuous.
 
The reason for my question is that I am taking a master pre-exam and one of the prep questions asked the following .... what is the MINIMUM number of 120v 15a general lighting branch Circuits for a 2100sqft dwelling ?

My answer was ..... 2100sqft x 3va =6300 divided by 1800 = 3.5 4 circuits

5 questions later it asked the following.....What is the LEAST amount of general lighting circuits required for a 6,000 sqft bank ?

I did my math the same as the dwelling question above and my answer was wrong because I did not include 125%

Is the 125% required for non dwelling and not required for dwelling?

Thank you
 
Fred B said:
The 125% comes into play when sizing conductors for a feeder 215.2(A)(1)(a), or for branch circuit wiring with continuous loads per 210.19(A)(1)(a).
Lighting can be a continuous load in non dwelling occupancies, a lot of times it is more likely a combination of continuous and non-continuous.
Click to expand...
Fred, you answered my question. Thank you sir
 
Every calculation I have seen for lighting in a non dwelling there was always a 125% for continuous use. There isn't many situations in a non dwelling where the lights wouldn't be on continuously
 
I believe all the table values in 220 for a given occupancy type has the continuous value build into the w/sq ft numbers, so you should not have to add or multiply by 1.25.
This would apply to service sizing, not feeders or bc’s.
 
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