To calculate that number, divide the VA rating of the circuit by 180VA for each receptacle strap.If youd like to see updated information on this topic, please check out this recently published article, Load Calculations Part 1.For example, you must know the definitions in Art.Art. 210 says about continuous loads, and understand the overcurrent protection requirements set forth in Art.
Thus when you calculate branch-circuit, feeder, and service loads, you must use a nominal system voltage of 120V, 120240V, 208Y120V, 240V, 347V, 480Y277V, 480V, 600Y347V, or 600V unless otherwise specified (220.2) ( Fig. When the ampere calculation exceeds a whole number by 0.5 or more, round up to the next whole number. For, example, round 29.5A up to 30A, but round 29.45A down to 29A. For example, youll find motors in Art. Art. 440. To know if you should look in another Article, use the NEC index. Unless specified otherwise, loads shall be computed using the nominal system voltage such as 120V, 120240V, 208Y120V, 240V, 347V, 480Y277V, 480V, 600Y347V or 600V. Calculate the feeder demand load for dryers at 100 of the appliance rating. If the dryers run continuously, you must size the conductor and protection device at 125 of the load 210.19(A), 215.3, and 230.42. Table 220.18 demand factors dont apply to commercial dryers. What size branch-circuit conductor and overcurrent protection does the NEC require for a 7kW dryer rated 240V when the dryer is in a multi-family dwelling laundry room ( Fig. Therefore, you must use a 30A breaker with a 10 AWG conductor. The reduced demand factors for multiple dryers (Table 220.18) dont apply in a commercial setting. Calculate the feederservice demand load for electric heating equipment at 100 of the total heating load. The feeder or service demand load cant be less than the sum of the two largest appliance loads. The demand factors of Table 220.20 dont apply to space-heating, ventilating, or air-conditioning equipment. You can assume a laundry circuit isnt a continuous load and that commercial laundry circuits are rated 1,500VA unless noted otherwise in the project drawings or exam question. Calculate it at 125 of the general lighting load listed in Table 220.3(A). For service calculations, consider every 5 feet (or less) of multi-outlet receptacle assembly to be 180VA. When you can reasonably expect a multi-outlet receptacle assembly to power several appliances simultaneously, consider each foot (or less) as 180VA for service calculations. Normally, a multi-outlet receptacle assembly isnt a continuous load 220.3(B)(8). Electrical Panel Load Calculation Trial Circuit DependsThe maximum number of receptacle outlets permitted on a commercial or industrial circuit depends on the circuit ampacity.
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