Z-51 Questions with Detailed Verified Answers

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Z-51 Questions with Detailed Verified
Answers

Question:How do automatic expansion valves work?

Ans: Evaporator pressure closes the valve and spring pressure opens the
valve.

Question: When will a faulty check valve cause the most damage?

Ans: On startup.

Question: What will happen if a TEV'S sensing bulb insulation wears off of the
suction line in an 85 F Degree room?

Ans: You will flood the evaporator.

Question: What can a clogged pump strainer cause?

Ans: A reduction or loss in water flow which will lead to high condenser head
pressure.

Question: What part of the Refrigeration system is the solenoid valve part of?

Ans: The pump down cycle (Thermostat - Solenoid Valve - Low Pressure
Controller).

Question: What is the proper machine start up procedure?

Ans: Check oil, start chilled water pump, start condenser water pump, start
tower fans and start up machine.

Question: How does a reciprocating machine cycle compressors on and off?

Ans: Through the use of the low pressure control.

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Question: What refrigerant has the best Refrigeration effect and highest
latent heat?

Ans: Ammonia (R-717) / ASHRE Classification is B2.

Question: What is the leaving water temperature of an induced draft cooling
tower that is operating efficiently?

Ans: At some temperature between the dry and wet bulb temperature.

Question: What could a sudden reduction in the supply flow of the cooling
tower water result in?

Ans: An increase in head pressure.

Question: How do reciprocating compressor unloaders operate?

Ans: By keeping the compressor suction valves open.

Question: Which side of the compressor is R-22 vapor charged into?

Ans: The suction side.

Question: What should the percentage of lubricant circulated through a well
designed system be?

Ans: Lubricant should not exceed 10%.

Question: What is oil foaming in the compressor a result of?

Ans: Liquid refrigerant in the crankcase.

Question: What is the main reason for installing an oil separator on the
discharge line?

Ans: To return oil back to the compressor crank case.

Question: What causes the foaming of oil in a reciprocating compressor using
the splash system for lubrication?

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Ans: A rapid decrease in pressure.

Question: What is the purpose of oil in a refrigerant compressor?

Ans: It reduces ware and friction.

Question: What is a filter dryer used to remove?

Ans: Moisture, particles and contaminants.

Question: Where in a refrigeration system is the oil separator located?

Ans: On the discharge line as far from the compressor as possible.

Question: If a motor has 4 belts and 1 of the 4 belts are worn, how many belts
should be replaced?

Ans: All of the belts should be replaced.

Question: Does a solenoid valve vary or control the flow of refrigerant?

Ans: No.

Question: What accessory meters and controls the flow of refrigerant into the
evaporator?

Ans: The TEV (Metering Device).

Question: What will occur if you use an automatic expansion valve with a
variable load?

Ans: You will starve the evaporator.

Question: What does an automatic expansion valve do?

Ans: It maintains a constant evaporator pressure.

Question: What could cause the evaporator to not respond to the
adjustments of the TEV?

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Ans: Oil logged on the low side.

Question: What can non-condensible's cause?

Ans: High head pressure.

Question: When will compressor motor horsepower increase?

Ans: It will increase as the head pressure increases.

Question: When will compressor motor horsepower decrease?

Ans: As the suction pressure increases.

Question: When using a brine solution in a system what can be used to
prevent rusting?

Ans: Di-Chromate Tablets.

Question: What would cause a Halide torch flame to turn yellow?

Ans: A clogged sample tube.

Question: What is the purpose of having 2 compressors in a cascade system?

Ans: To operate and very low temperatures and avoid high compression ratio.

Question: Why is a pressure relief valve better than a fusible plug?

Ans: Because it can be re-seated and is cost efficient.

Question: What could cause compressor knocking?

Ans: Liquid refrigerant slugging the compressor.

Question: What would occur if a TEV'S spring were to break?