NATE Refrigeration

Question 1

What is the refrigeration effect and how is it calculated?

Accepted Answer

Heat absorbed in the evaporator; calculated as evaporator outlet enthalpy minus evaporator inlet enthalpy

Answer

The refrigeration effect is the heat absorbed per pound of refrigerant in the evaporator, equal to the enthalpy difference across the evaporator.

Question 2

What refrigerant is commonly used in medium-temperature commercial refrigeration cases in the US?

Accepted Answer

R-404A / R-448A

Answer

R-404A has been the standard for medium-temperature commercial refrigeration, and R-448A is the common lower-GWP replacement.

Question 3

What does a suction line accumulator protect in a refrigeration system?

Accepted Answer

Compressor from liquid refrigerant slugging

Answer

The accumulator traps liquid refrigerant on the suction line, boiling it off slowly rather than allowing it to enter and damage the compressor.

Question 4

At what temperature range does a medium-temperature refrigeration system typically maintain a reach-in display case?

Accepted Answer

28°F to 40°F

Answer

Medium-temperature refrigeration maintains product temperatures between 28°F and 40°F for dairy, deli, and produce applications.

Question 5

What is the purpose of a filter-drier in a refrigeration system?

Accepted Answer

Remove moisture and contaminants from the refrigerant circuit

Answer

The filter-drier contains desiccant that absorbs moisture and a filter screen that traps particulates to protect the metering device and compressor.

NATE - North American Technician Excellence Practice Test