Rhode Island - Unit 28 Review Questions - Troubleshooting and Typical Operating Conditions for Commercial Refrigeration Review Questions

What is the first thing a technician should know before beginning troubleshooting?

Knowing the correct operating pressures for a typical system. Also knowing how the equipment is supposed to function, how it sounds, whether it should be hot or cool, and when a fan should be operating. pg 649

What is the coil-to-air temperature relationship for a refrigeration system designed for minimum food dehydration? ABCD

D) 8 - 12 F pg 650

When food dehydration is not a factor, the coil-to-air temperature relationship is _____ to _____ F.

16 to 22 pg 650

How is minimum food dehydration accomplished?

By keeping the relative humidity to 90% and the temperature differential of refrigerant to air at 8 - 12 F. pg 650

Why is minimum dehydration not used on every job?

Not all foods need minimum dehydration. pg 650

What is the coil-to-air temperature relationship for an average coil where dehydration is not a factor?

16 - 22 pg 650

At what evaporator temperature does an ice maker usually begin to make ice? ABCD

D) 20 F. pg 652

What is the evaporator coil-to-air relationship when the compressor is not running?

When the compressor is off and the box temperature is up to its highest point, the coil pressure would correspond to the air temperature in the box. pg 650

What is meant by the term approach when dealing with an evaporator chilling water?

It is the difference between the evaporating temperature and the leaving-water temperature. The more efficient the heat exchange between the evaporating refrigerant and the water, the smaller the approach will be. pg 662

How can an evaporator be tested for efficiency?

To check the evaporator for efficiency, check to make sure the superheat is correct and that the evaporator has the correct amount of refrigerant. pg 661

How can a condenser be tested for efficiency?

Check for high head pressures and low subcooling. pg 663

How can a hermetic compressor be tested for efficiency?

Perform a compressor vacuum test to see if there are any bad valves. pg 668

A TXV system responds to an overcharge of refrigerant by? ABCD

B) High head pressure. Any overcharge will cause an increase in discharge pressure. pg 660

An automatic expansion valve system responds to an overcharge of refrigerant by? ABCD

B) High head pressure. Any overcharge will cause an increase in discharge pressure. pg 660

A capillary tube system responds to an overcharge of refrigerant by? ABCD

D) all of the above. It will have high suction pressure, high head pressure, and possibly a flooded compressor. pg 659 and 660

How does TXV respond to an undercharge?

The system will be starved and the suction gage and the discharge gage will read low. pg 688

How does Automatic expansion valve respond to an undercharge?

The AXV maintains a constant low-side pressure, so the low-side pressure does not go down when there is an undercharge. pg 688

How does capillary tube respond to an undercharge?

The system will be starved and the suction gage and the discharge gage will read low. pg 688