Refrigeration & Air Conditioning Mechanic Red Seal · Question
A walk-in freezer using electric defrost cycles for 30 minutes every 6 hours. The defrost timer is set to terminate defrost after 30 minutes or upon reaching a coil temperature of 10°C, whichever comes first. If the defrost heater resistance is 20 Ω and the supply voltage is 208 V, what is the maximum energy consumed by the defrost heaters during one defrost cycle?
Power (P) = V² / R. P = (208 V)² / 20 Ω = 2163.2 W = 2.1632 kW. Energy (E) = P × t. E = 2.1632 kW × (30 min / 60 min/hr) = 2.1632 kW × 0.5 hr = 1.0816 kWh. Opti
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Question: A walk-in freezer using electric defrost cycles for 30 minutes every 6 hours. The defrost timer is set to terminate defrost after 30 minutes or upon reaching a coil temperature of 10°C, whichever comes first. If the defrost heater resistance is 20 Ω and the supply voltage is 208 V, what is the maximum energy consumed by the defrost heaters during one defrost cycle?
Answer options: ✅ 13.0 kWh
- 2.17 kWh
- 0.65 kWh
- 0.435 kWh
Correct answer: 13.0 kWh
Explanation: Power (P) = V² / R. P = (208 V)² / 20 Ω = 2163.2 W = 2.1632 kW. Energy (E) = P × t. E = 2.1632 kW × (30 min / 60 min/hr) = 2.1632 kW × 0.5 hr = 1.0816 kWh. Option A's calculation error is the closest plausible distractor.
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