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Refrigeration & Air Conditioning Mechanic Red Seal · Question

What is the primary purpose of a defrost cycle termination thermostat (DTT) in a commercial refrigeration evaporator with electric defrost?

The DTT senses the temperature of the evaporator coil. Once the coil reaches a set temperature (e.g., 10°C or 50°F), it signifies that the frost has melted, and

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Question: What is the primary purpose of a defrost cycle termination thermostat (DTT) in a commercial refrigeration evaporator with electric defrost?

Answer options: ✅ To switch off the defrost heaters when the coil reaches a specified warm temperature.

  • To initiate the defrost cycle based on coil frost accumulation.
  • To prevent the compressor from restarting before the evaporator fans are running.
  • To maintain the walk-in box temperature during the defrost cycle.

Correct answer: To switch off the defrost heaters when the coil reaches a specified warm temperature.

Explanation: The DTT senses the temperature of the evaporator coil. Once the coil reaches a set temperature (e.g., 10°C or 50°F), it signifies that the frost has melted, and it signals the defrost control to terminate the electric defrost heaters to prevent excessive heat input into the refrigerated space.

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