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Z-51 TEST 2025 LATEST 400 REAL EXAM
QUESTIONS AND CORRECT ANSWERS/ Z-51
REFRIGERATION TEST EXAM
How many phases will a 3 HP motor use? - ANSWER ✔✔- 3 Phases.
If you were running 3 compressors what would the state of the refrigerant be
leaving the 3rd evaporator coil? - ANSWER ✔✔- It would be a slightly
superheated vapor.
What does a TEV do? - ANSWER ✔✔- It restricts the amount of refrigerant that
flows from the high side to the low side.
When does a halide torch turn from blue to green or purple? - ANSWER ✔✔-
When a leak is detected.
What does a rectifier do? - ANSWER ✔✔- It converts AC voltage to DC voltage.
What is the function of a thermostat? - ANSWER ✔✔- It's purpose is to cycle the
compressor on and off.
What is the main purpose for a crankcase breather line? - ANSWER ✔✔- The
main purpose is to prevent oil from slugging the compressor.
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Where can the middle port on manifold gauges be connected to? - ANSWER ✔✔-
It can be connected to the recovery machine, charging cylinder or vacuum pump.
Why is a forced draft cooling tower better than a natural draft cooling tower? -
ANSWER ✔✔- Because it is smaller and it is not affected by prevailing winds.
What should an RMO do after recovering as a liquid when attempting to open the
chiller for servicing? - ANSWER ✔✔- You should next, recover as a vapor and
then proceed to open the chiller for servicing.
What is the proper way to start up a pump? - ANSWER ✔✔- Open the suction
valve and then slowly throttle open the discharge.
How do automatic expansion valves work? - ANSWER ✔✔- Evaporator pressure
closes the valve and spring pressure opens the valve.
When will a faulty check valve cause the most damage? - ANSWER ✔✔- On
startup.
What will happen if a TEV'S sensing bulb insulation wears off of the suction line
in an 85 F Degree room? - ANSWER ✔✔- You will flood the evaporator.
What can a clogged pump strainer cause? - ANSWER ✔✔- A reduction or loss in
water flow which will lead to high condenser head pressure.
What part of the Refrigeration system is the solenoid valve part of? - ANSWER
✔✔- The pump down cycle (Thermostat - Solenoid Valve - Low Pressure
Controller).
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What is the proper machine start up procedure? - ANSWER ✔✔- Check oil, start
chilled water pump, start condenser water pump, start tower fans and start up
machine.
How does a reciprocating machine cycle compressors on and off? - ANSWER
✔✔- Through the use of the low pressure control.
What refrigerant has the best Refrigeration effect and highest latent heat? -
ANSWER ✔✔- Ammonia (R-717) / ASHRE Classification is B2.
What is the leaving water temperature of an induced draft cooling tower that is
operating efficiently? - ANSWER ✔✔- At some temperature between the dry and
wet bulb temperature.
What could a sudden reduction in the supply flow of the cooling tower water result
in? - ANSWER ✔✔- An increase in head pressure.
How do reciprocating compressor unloaders operate? - ANSWER ✔✔- By keeping
the compressor suction valves open.
Which side of the compressor is R-22 vapor charged into? - ANSWER ✔✔- The
suction side.
What should the percentage of lubricant circulated through a well designed system
be? - ANSWER ✔✔- Lubricant should not exceed 10%.
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What is oil foaming in the compressor a result of? - ANSWER ✔✔- Liquid
refrigerant in the crankcase.
What is the main reason for installing an oil separator on the discharge line? -
ANSWER ✔✔- To return oil back to the compressor crank case.
What causes the foaming of oil in a reciprocating compressor using the splash
system for lubrication? - ANSWER ✔✔- A rapid decrease in pressure.
What is the purpose of oil in a refrigerant compressor? - ANSWER ✔✔- It reduces
ware and friction.
What is a filter dryer used to remove? - ANSWER ✔✔- Moisture, particles and
contaminants.
Where in a refrigeration system is the oil separator located? - ANSWER ✔✔- On
the discharge line as far from the compressor as possible.
If a motor has 4 belts and 1 of the 4 belts are worn, how many belts should be
replaced? - ANSWER ✔✔- All of the belts should be replaced.
Does a solenoid valve vary or control the flow of refrigerant? - ANSWER ✔✔-
No.
What accessory meters and controls the flow of refrigerant into the evaporator? -
ANSWER ✔✔- The TEV (Metering Device).
Z-51 TEST 2025 LATEST 400 REAL EXAM
QUESTIONS AND CORRECT ANSWERS/ Z-51
REFRIGERATION TEST EXAM
How many phases will a 3 HP motor use? - ANSWER ✔✔- 3 Phases.
If you were running 3 compressors what would the state of the refrigerant be
leaving the 3rd evaporator coil? - ANSWER ✔✔- It would be a slightly
superheated vapor.
What does a TEV do? - ANSWER ✔✔- It restricts the amount of refrigerant that
flows from the high side to the low side.
When does a halide torch turn from blue to green or purple? - ANSWER ✔✔-
When a leak is detected.
What does a rectifier do? - ANSWER ✔✔- It converts AC voltage to DC voltage.
What is the function of a thermostat? - ANSWER ✔✔- It's purpose is to cycle the
compressor on and off.
What is the main purpose for a crankcase breather line? - ANSWER ✔✔- The
main purpose is to prevent oil from slugging the compressor.
,2|Page
Where can the middle port on manifold gauges be connected to? - ANSWER ✔✔-
It can be connected to the recovery machine, charging cylinder or vacuum pump.
Why is a forced draft cooling tower better than a natural draft cooling tower? -
ANSWER ✔✔- Because it is smaller and it is not affected by prevailing winds.
What should an RMO do after recovering as a liquid when attempting to open the
chiller for servicing? - ANSWER ✔✔- You should next, recover as a vapor and
then proceed to open the chiller for servicing.
What is the proper way to start up a pump? - ANSWER ✔✔- Open the suction
valve and then slowly throttle open the discharge.
How do automatic expansion valves work? - ANSWER ✔✔- Evaporator pressure
closes the valve and spring pressure opens the valve.
When will a faulty check valve cause the most damage? - ANSWER ✔✔- On
startup.
What will happen if a TEV'S sensing bulb insulation wears off of the suction line
in an 85 F Degree room? - ANSWER ✔✔- You will flood the evaporator.
What can a clogged pump strainer cause? - ANSWER ✔✔- A reduction or loss in
water flow which will lead to high condenser head pressure.
What part of the Refrigeration system is the solenoid valve part of? - ANSWER
✔✔- The pump down cycle (Thermostat - Solenoid Valve - Low Pressure
Controller).
,3|Page
What is the proper machine start up procedure? - ANSWER ✔✔- Check oil, start
chilled water pump, start condenser water pump, start tower fans and start up
machine.
How does a reciprocating machine cycle compressors on and off? - ANSWER
✔✔- Through the use of the low pressure control.
What refrigerant has the best Refrigeration effect and highest latent heat? -
ANSWER ✔✔- Ammonia (R-717) / ASHRE Classification is B2.
What is the leaving water temperature of an induced draft cooling tower that is
operating efficiently? - ANSWER ✔✔- At some temperature between the dry and
wet bulb temperature.
What could a sudden reduction in the supply flow of the cooling tower water result
in? - ANSWER ✔✔- An increase in head pressure.
How do reciprocating compressor unloaders operate? - ANSWER ✔✔- By keeping
the compressor suction valves open.
Which side of the compressor is R-22 vapor charged into? - ANSWER ✔✔- The
suction side.
What should the percentage of lubricant circulated through a well designed system
be? - ANSWER ✔✔- Lubricant should not exceed 10%.
, 4|Page
What is oil foaming in the compressor a result of? - ANSWER ✔✔- Liquid
refrigerant in the crankcase.
What is the main reason for installing an oil separator on the discharge line? -
ANSWER ✔✔- To return oil back to the compressor crank case.
What causes the foaming of oil in a reciprocating compressor using the splash
system for lubrication? - ANSWER ✔✔- A rapid decrease in pressure.
What is the purpose of oil in a refrigerant compressor? - ANSWER ✔✔- It reduces
ware and friction.
What is a filter dryer used to remove? - ANSWER ✔✔- Moisture, particles and
contaminants.
Where in a refrigeration system is the oil separator located? - ANSWER ✔✔- On
the discharge line as far from the compressor as possible.
If a motor has 4 belts and 1 of the 4 belts are worn, how many belts should be
replaced? - ANSWER ✔✔- All of the belts should be replaced.
Does a solenoid valve vary or control the flow of refrigerant? - ANSWER ✔✔-
No.
What accessory meters and controls the flow of refrigerant into the evaporator? -
ANSWER ✔✔- The TEV (Metering Device).
