HV014 - Study Guide

Explain why a technician should wear safety gear when handling liquid nitrogen.

Exposure can result in severe cold burns and frostbite

Explain the harvest process in an ice machine with a vertical cube evaporator.

Hot gas from the compressor's discharge line is directed through the evaporator to warm up and loosen the cubes from their molds. The sheet of ice cubes falls and breaks apart into individual cubes in the storage bin.

Explain why it is important for compressed air to be dry when used in manufacturing and industrial processing

Moisture may rust tools

Explain the harvest phase in an ice machine with an inverted cube evaporator.

Once the ice cubes are formed, the ice molds are warmed until the cubes fall out due to gravity. The warming is done by electric heating elements or hot-gas defrost operation. The cubes drop down onto a deflector tray, slide through a chute, and arrive in the ice cube storage bin.

Explain what will happen if a keel cooler is undersized.

The head pressure can become excessively high

Explain why the secondary loop piping should be insulated.

To maximize efficiency by minimizing the absorption of heat from any unconditioned space.

Explain why the suction line should slope downward to the compressor.

To permit oil drainage

Why is it necessary for a trap to be at the bottom of a compressor discharge line riser?

To prevent oil and liquid refrigerant from returning to a compressor

Identify four variables that affect the selection of the compressor, condenser, and evaporator.

capacity of metering device, temperature control, air circulation, duty of the system.

List three factors that affect suction line temperature.

defrost method, design temperature , relative humidity,evaporator temperature difference.

Explain why a vertical suction riser should have a smaller diameter than a horizontal suction line.

helps maintain minimum velocity for oil return.

Why is it critical to maintain the proper refrigerant velocity in the suction line?

so oil is returned to the compressor.

Explain what will happen if a keel cooler is oversized.

will provide too much subcooling when the boat is in cold water.