One method of controlling the capacity of reciprocating compressors is to bypass the discharge from one or more cylinders back to the suction side of the compressor. The control is called

One method of controlling the capacity of reciprocating compressors is to bypass the discharge from one or more cylinders back to the suction side of the compressor. The control is called

a) compressor unloading
b) damping
c) suction throttling
d) cylinder bypass
e) sectional evaporating






Answer: D

Which of the statements about automatic expansion valves is false?

Which of the statements about automatic expansion valves is false?

a) The valve maintains constant pressure in the evaporator during compressor operation regardless of the load.
b) When the compressor stops the valve automatically shuts off.
c) A spring exerting a downward force on the diaphragm tends to open the valve.
d) The spring force is countered by evaporator pressure acting upward against the diaphragm which closes the valve.
e) The control may be used with multiple cooling coils connected to the same compressor.

Answer: E

A method of controlling the capacity of reciprocating refrigeration compressors, whereby the discharge of high-pressure refrigerant is re-introduced to the suction side of the compressor, is called:

A method of controlling the capacity of reciprocating refrigeration compressors, whereby the discharge of high-pressure refrigerant is re-introduced to the suction side of the compressor, is called:

a. Compressor unloading
b. Cylinder throttling
c. Suction throttling
d. Hot gas bypass
e. Cylinder unloading






Answer: D

The most widely used refrigerant metering device, which consists of a pressure-sensitive bellows or diaphragm connected to a temperature sensing bulb, is a/an:

The most widely used refrigerant metering device, which consists of a pressure-sensitive bellows or diaphragm connected to a temperature sensing bulb, is a/an:

a. Thermostatic expansion valve
b. Automatic expansion valve
c. Capillary tube
d. Equalizer
e. Constant pressure valve






Answer: A

The simple, small-bore device that restricts the flow of liquid from the condenser to the evaporator and maintains a pressure difference between the two, is called:

The simple, small-bore device that restricts the flow of liquid from the condenser to the evaporator and maintains a pressure difference between the two, is called:

a. A high-pressure float valve
b. A low-pressure float valve
c. An equalizer line
d. A capillary tube
e. An intermediate valve (pressure reducing valve)





Answer: D

In a refrigeration system controlled by a high-pressure float valve, excessive refrigerant charge will cause

In a refrigeration system controlled by a high-pressure float valve, excessive refrigerant charge will cause 

a. Liquid carry-over to the compressor
b. The float chamber to become flooded
c. The evaporator to be starved of refrigerant
d. Frost formation on the evaporator
e. The compressor to run continuously






Answer: A

The type of operation that stops a refrigeration compressor when the temperature setpoint of the cooled substance is reached, then re-starts the compressor when the temperature set-point is exceeded, is called:

The type of operation that stops a refrigeration compressor when the temperature setpoint of the cooled substance is reached, then re-starts the compressor when the temperature set-point is exceeded, is called:

a. Intermittent operation
b. Continuous operation with reduced output
c. Cylinder bypass
d. Unloading
e. Variable guide vane operation






Answer: A

Which of the following statements about the evaporator bypass dampers in a refrigeration system is true?

Which of the following statements about the evaporator bypass dampers in a refrigeration system is true? 

a. They decrease the resistance to the passage of air when they close
b. When the face damper is closed, the quantity of air passing over the evaporator coils is at a maximum
c. The quantity of air passing through the duct depends on the damper position
d. Multi-speed blowers cannot be used in combination with face and bypass dampers
e. Actuators are required to provide damper movement

Answer: E

The automatic expansion valve in a refrigeration system operates on the principle of balancing:

The automatic expansion valve in a refrigeration system operates on the principle of balancing:

a. The volumetric expansion of a fluid against a return spring
b. Evaporator temperature against a return spring
c. Condenser pressure against a return spring
d. Condenser temperature against a return spring
e. Evaporator pressure against a return spring







Answer: E

In refrigeration systems, the most common methods used to control the capacity of a reciprocating compressor are:

In refrigeration systems, the most common methods used to control the capacity of a reciprocating compressor are:

a. Cylinder bypass and hot gas bypass
b. Intermittent operation and continuous operation
c. Cylinder unloaders and variable speed drives
d. Suction throttling and variable inlet vanes
e. Cylinder unloaders and cylinder bypass






Answer: B

What will the effect be if insufficient liquid refrigerant is admitted to the evaporator by a thermostatic expansion valve?

What will the effect be if insufficient liquid refrigerant is admitted to the evaporator by a thermostatic expansion valve?

a. Insufficient force will be generated against the diaphragm and spring to open the expansion valve
b. The heat in the vapour leaving the evaporator causes the pressure in the thermal element to increase opening the expansion valve
c. The room temperature will decrease closing the expansion valve
d. The thermal element reaches an equilibrium leaving the expansion valve in the same position
e. The expansion valve will fail to respond





Answer: B

The device that guides refrigerant vapour into a centrifugal compressor in the same direction as the compressor impeller is turning, is called a

The device that guides refrigerant vapour into a centrifugal compressor in the same direction as the compressor impeller is turning, is called a

a. Inlet damper
b. Cylinder bypass
c. Variable Inlet Guide Vanes
d. Damper control
e. Compressor unloader

Answer: C

Sectional evaporators, installed in a refrigeration plant, control their capacity by

Sectional evaporators, installed in a refrigeration plant, control their capacity by

a. Varying the quantity of air passing over the evaporator coils
b. Intermittent operation of the compressor
c. Using solenoid valves to stop the refrigerant flow to one or more evaporator sections
d. Altering the evaporator pressure in one or more of the evaporator sections
e. Switching gear in the compressor




Answer: C

In a refrigeration system controlled by a high pressure float valve, insufficient refrigerant charge will cause

In a refrigeration system controlled by a high pressure float valve, insufficient refrigerant charge will cause

a. Automatic system shut down
b. A boost in the compressor's discharge pressure
c. Liquid carry-over to the compressor
d. Starving of the evaporator and reduced cooling capacity
e. The compressor to run continuously





Answer: D

The thermostatic expansion valve operates on the principle of balancing:

The thermostatic expansion valve operates on the principle of balancing:

a. The volumetric expansion of a fluid against a return spring
b. Evaporator temperature against a return spring
c. Condenser pressure against a return spring
d. Condenser temperature against a return spring
e. Evaporator pressure against a return spring






Answer: A

In a refrigeration system, a weighted valve pin is used in a high-pressure float valve system in order to:

In a refrigeration system, a weighted valve pin is used in a high-pressure float valve system in order to:

a. Get proper pressure drop into the evaporator
b. Reduce frosting of the line immediately after the float valve
c. Allow the room temperature to be adjusted
d. Act as a pressure relief device
e. Prevent flooding of the evaporator






Answer: B

The control used in a mechanical refrigeration system to maintain a constant level of liquid refrigerant in the accumulator tank of a flooded evaporator is called

The control used in a mechanical refrigeration system to maintain a constant level of liquid refrigerant in the accumulator tank of a flooded evaporator is called

a. A thermostatic expansion valve
b. An automatic expansion valve
c. A low-pressure float valve
d. A hand operated expansion valve
e. A high-pressure float valve





Answer: C

Manual or hand-operated expansion valves are seldom used in modern refrigeration systems except, occasionally:

Manual or hand-operated expansion valves are seldom used in modern refrigeration systems except, occasionally:

a. To control the temperature of the evaporator
b. In the bypass line around the automatic control valve
c. To control the temperature of the cooling medium
d. In the compressor oil cooling system
e. To control the temperature of the condenser




Answer: B

Which of the following is NOT a refrigerant metering device?

Which of the following is NOT a refrigerant metering device?

a. Low-pressure float
b. Automatic expansion valve
c. Thermostat
d. Capillary tube
e. High-side float






Answer: C