What device will prevent a refrigeration compressor from running if suction drops below a predetermined point?

Prepare for the Master Mechanical License Test with flashcards and multiple-choice questions. Each question includes hints and detailed explanations. Get confident for your exam!

A low-pressure control is designed to monitor the suction pressure within a refrigeration system and will prevent the compressor from running if that pressure drops below a predetermined threshold. This is important for protecting the compressor from damage caused by low suction pressure, which can occur in situations such as refrigeration system leaks or insufficient refrigerant charge.

The low-pressure control acts as a safety mechanism. When the suction pressure falls below the set point, this switch opens the electrical circuit to the compressor, thereby preventing it from operating. This helps to maintain the integrity of the system and ensures that the compressor does not run in conditions where it could overheat or become damaged due to inadequate refrigerant flow.

Other devices listed serve different functions. A thermostatic expansion valve regulates the flow of refrigerant based on temperature changes, while a high-pressure switch monitors and reacts to excessive pressure. A fixed metering device is designed to control the flow of refrigerant but does not provide low-pressure protection for the compressor. Therefore, the low-pressure control is specifically tasked with ensuring that the compressor runs only under safe suction pressure conditions.

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