NATE Refrigeration 2

Question 1

What refrigerant is used in low-temperature frozen food applications and has an evaporating temperature around -20°F?

Accepted Answer

R-404A or R-448A

Answer

R-410A

Answer

R-22

Answer

R-134a

Question 2

What is the purpose of a hot gas defrost system in commercial refrigeration?

Accepted Answer

Melt frost from evaporator coils by circulating hot discharge gas through them instead of using electric heaters

Answer

Reheat supply air after cooling

Answer

Warm the compressor oil at startup

Answer

Prevent condensation on the case glass doors

Question 3

What causes a high compression ratio in a refrigeration system?

Accepted Answer

High condensing pressure and/or low evaporating pressure

Answer

Low ambient temperature

Answer

Oversized metering device

Answer

High suction superheat only

Question 4

What is the function of the oil separator in a commercial refrigeration system?

Accepted Answer

Separate compressor oil from the discharge gas and return it to the compressor crankcase

Answer

Remove moisture from refrigerant

Answer

Filter non-condensables from the system

Answer

Regulate oil temperature

Question 5

What is the typical evaporator TD (temperature difference) used to assess evaporator performance in a refrigeration system?

Accepted Answer

Difference between return air temperature and saturated suction temperature in the evaporator

Answer

Difference between condensing temperature and ambient

Answer

Difference between supply and return air temperatures

Answer

Difference between discharge and suction pressures in degrees

Question 6

What EPA regulation governs refrigerant handling and requires recovery before service of commercial refrigeration equipment?

Accepted Answer

EPA Section 608

Answer

EPA Section 404

Answer

Clean Water Act

Answer

OSHA 29 CFR 1910