Core Flashcards

Refrigerant leaving an evaporator should be in what state for proper system operation?

Answer: Low-pressure, low-temperature vapor (superheated)

The evaporator boils liquid refrigerant into low-pressure vapor that should leave slightly superheated.

In a refrigeration cycle, which component raises the refrigerant's pressure and temperature?

Answer: Compressor

The compressor increases both the pressure and temperature of the refrigerant vapor.

Why must a technician evacuate a system to a deep vacuum after recovery and before recharging?

Answer: To remove moisture and non-condensable gases such as air

Deep evacuation boils off moisture and pulls out air, preventing acid formation and poor performance.

What instrument provides the most accurate measurement of a deep vacuum during system evacuation?

Answer: An electronic micron (vacuum) gauge

A micron gauge reads vacuum levels far more accurately than a standard compound gauge.

Moisture left inside a refrigeration system can combine with refrigerant and oil to form what damaging substance?

Answer: Acids that corrode components and cause compressor failure

Moisture reacts to form acids that corrode internal parts and can destroy the compressor.

When charging a system with a near-azeotropic blend (such as a 400-series refrigerant), why should it generally be charged as a liquid?

Answer: The blend's components can fractionate, changing composition if charged as vapor

Zeotropic and near-azeotropic blends can fractionate during vapor charging, so they are charged as liquid to preserve composition.

A frost line forming partway along the evaporator or suction line most commonly indicates:

Answer: A restriction or low refrigerant charge

Frost at an abnormal point often signals a restriction or undercharge causing localized pressure drop.