A farm building has a 5 hp, three-phase, 230V motor for irrigation, a 10 kW electric water heater, and 500 VA of general lighting. What is the minimum calculated demand load for the farm building service, excluding the farm dwelling, according to NEC 220.102?

Correct answer: A. 14,500 VA

According to NEC 220.102(B), for feeder and service loads for farm buildings (excluding the dwelling), the two largest loads are calculated at 100%, the next largest at 75%, and the remaining at 25%. First, convert the 5 hp motor to VA. For a 5 hp, 230V, 3-phase motor, using Table 430.250 FLA is 15.2 A. VA = 15.2A * 230V * sqrt(3) = 6052 VA. Loads: 1) 10 kW (10,000 VA) water heater, 2) 6052 VA motor, 3) 500 VA general lighting. The two largest loads are the water heater (10,000 VA) and the motor (6052 VA). These are taken at 100%. The next largest is general lighting (500 VA), taken at 75%. Remaining (none) at 25%. So, 10,000 VA + 6052 VA + (500 VA * 0.75) = 10,000 VA + 6052 VA + 375 VA = 16,427 VA. This is approximately 16,500 VA. However, none of the options match exactly. Let me re-evaluate the motor calculation. NEC 220.102 (B) states 'The load for general-purpose farm buildings and loads for other farm buildings, shall be determined by the demand factors given in Table 220.102.' Table 220.102 does not list motor loads directly. It refers to the 'largest load', 'second largest load', etc. For motors, NEC 430.24 states the feeder capacity must be 125% of the largest motor's FLA plus the sum of the FLAs of all other motors. So, the motor load itself should be considered at 125% of its value for calculation, *then* apply the demand factors from 220.102. Let's re-calculate: Motor (5 hp, 3-ph, 230V): 15.2 A (Table 430.250). VA = 15.2 * 230 * sqrt(3) = 6052 VA. When considering the largest motor load for a service/feeder (not specifically for 220.102), it's 125% of the largest motor. So 6052 VA * 1.25 = 7565 VA. Now apply 220.102(B). Loads: 1) 10,000 VA (water heater), 2) 7565 VA (motor), 3) 500 VA (general lighting). Largest load (water heater): 10,000 VA * 100% = 10,000 VA. Second largest load (motor): 7565 VA * 100% = 7565 VA. Next largest load (general lighting): 500 VA * 75% = 375 VA. Total = 10,000 + 7565 + 375 = 17,940 VA. This is closest to 18,500 VA (D). Let's re-verify the motor calculation. NEC 220.102 (B) refers to Table 220.102, which is a demand factor table. It does not state to apply 125% to individual motor loads first before applying the demand factors in 220.102. It refers to the 'two largest loads.' So the original 6052 VA for the motor should be used. The 125% rule for motors is typically for sizing the feeder for the motor itself, or when calculating service loads where motor loads are combined with other loads, and the largest motor's full-load current is multiplied by 1.25, and then added to other loads. However, 220.102 (B) is a specific rule for farm buildings. It says 'The load for general-purpose farm buildings... shall be determined by the demand factors given in Table 220.102'. Table 220.102 lists 'Largest load', 'Second largest load', etc. It does not state to apply 125% to motors BEFORE applying these demand factors. Therefore, the motor load should be its calculated VA (6052 VA). Let's re-calculate with 6052 VA for motor. Loads: 1) 10,000 VA (water heater), 2) 6052 VA (motor), 3) 500 VA (general lighting). Largest load: 10,000 VA @ 100% = 10,000 VA. Second largest load: 6052 VA @ 100% = 6052 VA. Next largest load: 500 VA @ 75% = 375 VA. Total = 10,000 + 6052 + 375 = 16,427 VA. This is very close to 16,500 VA (C). So, the key here is whether to apply the 125% for the motor before applying the farm building demand factors. NEC 220.102 is a specific demand factor table for farm buildings. It implies the loads are already quantified. For motor loads, the 'load' itself is usually considered the FLA or a specific VA. The 125% factor is for feeder sizing, not necessarily for the 'load' value itself when applying demand factors. However, NEC 220.60 states: 'Where two or more motors or a motor(s) and other loads are connected to a feeder or service, the rating of the feeder or service shall be based on the sum of the following: (1) 125 percent of the full-load current rating of the highest rated motor. (2) The full-load current rating of all other motors. (3) The nameplate ampere or kVA rating of all other loads that are connected to the feeder or service.' This implies that the 125% factor is applied to the largest motor load *before* combining it with other loads for the overall feeder/service calculation. Therefore, it should be applied. My previous calculation of 17,940 VA (closest to D) was correct. Let's re-confirm the motor VA: 5 hp, 3-ph, 230V. Table 430.250: 15.2 A. VA = 15.2 A * 230 V * sqrt(3) = 6052 VA. Largest motor load (for calculation per 220.60) = 6052 VA * 1.25 = 7565 VA. So the loads are: Water heater: 10,000 VA. Motor (calculated): 7565 VA. General lighting: 500 VA. Now apply NEC 220.102(B) and Table 220.102: 1. Largest load (Water Heater): 10,000 VA * 100% = 10,000 VA. 2. Second largest load (Motor): 7565 VA * 100% = 7565 VA. 3. Next largest load (General Lighting): 500 VA * 75% = 375 VA. Total Demand Load = 10,000 VA + 7565 VA + 375 VA = 17,940 VA. This is closest to 18,500 VA (D). The options are rounded, so 17,940 VA is closest to 18,500 VA. Let me recheck the options. This is a hard question due to the combination of motor calculation and farm building demand factors. Let's re-evaluate the closest option. 17,940 VA is closer to 18,500 VA than 16,500 VA. Therefore, D is the most plausible answer.