Computed Load Calculations

[deee]

These steps "1 through 8" are what I follow when doing load calculations. The question at the bottom of the page is one that I run across that doesn't seem to fit into my steps here. Step #4 and Step #7. Maybe someone can tell me if they apply or they don't and why.

Computed Load Calculations for Store Room​

1. General Lighting Loads (sq/ft area) 220.12 Use Table 220.12 to calculate minimum light load and 220.15(a) says to use demand factor of 125% for calculating minimum calculated load.

1. Receptacles 220.14 says to use 220.14(I) to calculate the receptacle loads at 180va each. 220.44 allows the demand factors of Table 220.44

1. Show Window Lighting if used.220.14(G)(2) Says 200va per 1ft and 220.44(A) says 200va per linear foot; However 220.44(B) is considering Tract Lighting and has 150va per sq/ft added if used. 210.19(A)(1)(a) says to use the demand of 125% for continuous loads. Generally Lighting loads are considered continuous in commercial applications.

1. Combine the General lighting Loads 220.42 says to use the demand factors of Table 220.42

1. Water Heater or Specific Appliance, if used. 220.14(A) says for a specific appliance use the nameplate current rating.

1. Motor Loads. "ACs are considered Hermetic." 220.50 says to use 430.24, 430.25, 430.26 and for hermetic refrigerant motor compressors use 440.6(A) which states the name plate current ratting shall be used.

1. Outside Sign and Lighting. (Only if used on a TEST.) 220.14(F) says to calculate a minimum of 1200va for required branch circuit specified by 600.5. 600.5(A) states "Each commercial building and each commercial occupancy accessible to pedestrians shall be provided with at least one outlet in an accessible location at each entrance to each tenant space for sign and outline lighting system use."

1. Combine the loads and divide by the voltage (multiply the voltage by 1.732 for 3 phase to get the corrected voltage) to get the computed load.

What is the computed load for a store room with the following? 2300 sq/ft of floor area.70 receptacles, 15 ft of show window, a 24 amp 3phase air conditioner, a120 volt 1500 watt water heater. The service is a 120/208 wye.

 

[jrohe]

I am assuming by the "store room" in the question, the question is referring to a "store," as a "storage space" within another occupancy would not likely have 70 receptacles, 15 feet of show window, or a water heater. Because I am assuming this is a "store," my calculations below also include provisions for one exterior sign although the sign is not mentioned in the question.

Base Loads
General Lighting: 3 VA/sf * 2300 sf = 6900 VA
Receptacles: 70 receptacles * 180 VA/receptacle = 12600 VA
Show Window Lighting: 200 VA/lf * 15 lf = 3000 VA
HVAC: 24 amps * 208 volts * sqrt(3) = 8647 VA
Water Heating: 1500 watts (VA)
Exterior Sign: 1200 VA

Demand Loads
General Lighting: No demand factor permitted by T220.42. Demand load = 6900 VA.
Receptacles: (12600 VA - 10000VA) * 0.5 + 10000 VA = 11300 VA
Show Window Lighting: No demand factor permitted. Demand load = 3000 VA
HVAC: No demand factor permitted. Demand load = 8647 VA
Water Heating: No demand factor permitted. Demand load = 3000 watts (VA)
Exterior Sign: 1200 VA

Noncontinuous Demand Load Summary
Receptacles: 11300 VA
HVAC: 8647 VA
Water Heating: 3000 watts (VA)
Total: 22947 VA

Continuous Demand Load Summary
General Lighting: 6900 VA
Show Window Lighting: 3000 VA
Exterior Sign: 1200 VA
Total: 11100 VA

Feeder or Service Sizing Load
Noncontinuous Demand Load: 22947 VA
Continuous Demand Load: 11100 VA * 125% = 13875 VA
Total: 36822 VA
Equivalent Amps: 36822 VA / (208 * sqrt(3)) = 102.3 amps

 

[Dennis Alwon]

Duplicate-- Go Here