RETA CIRO REFRIGERATION CONTROLS
AND CONTROL CIRCUITS PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
Question 1
A reciprocating refrigeration compressor is controlled by a low-pressure
switch operating in pump-down mode. The thermostat calls for cooling,
the liquid-line solenoid valve opens, suction pressure rises, and the low-
pressure control closes its contacts to start the compressor. When the
thermostat is satisfied, the liquid-line solenoid closes. The compressor
continues running until the suction pressure falls to the low-pressure
cutout setting. What is the primary purpose of this control arrangement?
A. To maintain a constant discharge pressure
B. To prevent the evaporator from becoming flooded during shutdown
C. To remove refrigerant from the evaporator and suction line during the
off cycle
D. To prevent the condenser from becoming overfilled with liquid
refrigerant
Answer: C. To remove refrigerant from the evaporator and suction
line during the off cycle
Rationale: A pump-down control system uses a liquid-line solenoid
valve to stop refrigerant flow when the thermostat is satisfied. The
compressor continues operating until the suction pressure falls to the
low-pressure cutout setting, effectively pumping most of the refrigerant
1
,out of the evaporator and suction side. This reduces refrigerant
migration and helps prevent liquid refrigerant from reaching the
compressor during shutdown. The low-pressure switch is therefore
acting as a compressor-start/stop control in response to suction
pressure, not as a discharge-pressure regulator.
Question 2
A refrigeration compressor will not start even though the thermostat is
calling for cooling. Measurements show that control voltage is present
on the incoming side of the low-pressure control, but no voltage is
present on the outgoing side. The suction pressure is below the control's
cut-in setting. What is the most likely explanation?
A. The high-pressure control is stuck closed
B. The low-pressure control is open because suction pressure is below
its cut-in setting
C. The compressor contactor coil is shorted
D. The liquid-line solenoid is stuck open
Answer: B. The low-pressure control is open because suction
pressure is below its cut-in setting
Rationale: A low-pressure control used for compressor control opens
when suction pressure falls below its cutout setting and generally does
not reclose until pressure rises to the cut-in setting. If the pressure
remains below cut-in, the control circuit remains open and the
compressor cannot receive the command to start. A technician should
understand the difference between cut-in and cutout settings rather
than automatically assuming that a low-pressure switch should close
whenever pressure is low. In a pump-down system, a low suction
pressure with the liquid-line solenoid closed is normal during
shutdown.
2
,Question 3
A normally closed high-pressure safety control is installed in series with
a compressor contactor coil. During operation, condenser pressure rises
excessively and the control opens. Which statement best describes the
immediate electrical effect?
A. The compressor contactor coil is de-energized
B. The condenser fan motor is forced to run continuously
C. The liquid-line solenoid opens
D. The evaporator pressure regulator increases its pressure setting
Answer: A. The compressor contactor coil is de-energized
Rationale: A normally closed high-pressure safety control permits the
compressor control circuit to remain energized under normal
conditions. When excessive discharge pressure causes the safety to
open, the circuit to the compressor contactor coil is interrupted. The
contactor drops out, disconnecting power to the compressor motor.
This is a protective function intended to prevent dangerously high
condensing pressure and associated mechanical, thermal, and
electrical stress. The control does not itself regulate condenser
pressure; it interrupts operation when the pressure exceeds its safety
threshold.
Question 4
A technician is troubleshooting a refrigeration control circuit containing
a transformer, thermostat, liquid-line solenoid, low-pressure switch,
high-pressure switch, compressor contactor, and compressor motor. The
compressor does not run. The technician measures proper voltage at the
transformer secondary but finds zero volts across the contactor coil.
What should the technician determine next?
3
, A. Whether the compressor crankcase heater has failed
B. Which series safety or operating control is open
C. Whether the compressor has a low oil level
D. Whether the condenser coil is dirty
Answer: B. Which series safety or operating control is open
Rationale: When a contactor coil has no voltage across it, the first
objective is to determine why the control circuit is not completing the
electrical path. Controls such as thermostats, pressure switches,
overloads, oil-pressure controls, and other safeties may be wired in
series with the coil. A systematic voltage-tracing procedure identifies
the exact point where control voltage is lost. Mechanical compressor
conditions such as oil level or a dirty condenser may cause operational
problems but do not explain the absence of voltage at the contactor
coil unless a related safety has opened.
Question 5
A refrigeration system uses a thermostat with normally open contacts
that close when the controlled space temperature rises above the
setpoint. What happens when the thermostat calls for cooling?
A. The thermostat interrupts the compressor control circuit
B. The thermostat closes its contacts and completes the control circuit
C. The thermostat increases refrigerant pressure mechanically
D. The thermostat closes the high-pressure safety circuit permanently
Answer: B. The thermostat closes its contacts and completes the
control circuit
Rationale: In a conventional cooling control arrangement, a rise in
space temperature above the thermostat's cooling setpoint causes the
thermostat contacts to close. This closure permits control voltage to
pass through the remainder of the circuit and energize the appropriate
4
AND CONTROL CIRCUITS PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
Question 1
A reciprocating refrigeration compressor is controlled by a low-pressure
switch operating in pump-down mode. The thermostat calls for cooling,
the liquid-line solenoid valve opens, suction pressure rises, and the low-
pressure control closes its contacts to start the compressor. When the
thermostat is satisfied, the liquid-line solenoid closes. The compressor
continues running until the suction pressure falls to the low-pressure
cutout setting. What is the primary purpose of this control arrangement?
A. To maintain a constant discharge pressure
B. To prevent the evaporator from becoming flooded during shutdown
C. To remove refrigerant from the evaporator and suction line during the
off cycle
D. To prevent the condenser from becoming overfilled with liquid
refrigerant
Answer: C. To remove refrigerant from the evaporator and suction
line during the off cycle
Rationale: A pump-down control system uses a liquid-line solenoid
valve to stop refrigerant flow when the thermostat is satisfied. The
compressor continues operating until the suction pressure falls to the
low-pressure cutout setting, effectively pumping most of the refrigerant
1
,out of the evaporator and suction side. This reduces refrigerant
migration and helps prevent liquid refrigerant from reaching the
compressor during shutdown. The low-pressure switch is therefore
acting as a compressor-start/stop control in response to suction
pressure, not as a discharge-pressure regulator.
Question 2
A refrigeration compressor will not start even though the thermostat is
calling for cooling. Measurements show that control voltage is present
on the incoming side of the low-pressure control, but no voltage is
present on the outgoing side. The suction pressure is below the control's
cut-in setting. What is the most likely explanation?
A. The high-pressure control is stuck closed
B. The low-pressure control is open because suction pressure is below
its cut-in setting
C. The compressor contactor coil is shorted
D. The liquid-line solenoid is stuck open
Answer: B. The low-pressure control is open because suction
pressure is below its cut-in setting
Rationale: A low-pressure control used for compressor control opens
when suction pressure falls below its cutout setting and generally does
not reclose until pressure rises to the cut-in setting. If the pressure
remains below cut-in, the control circuit remains open and the
compressor cannot receive the command to start. A technician should
understand the difference between cut-in and cutout settings rather
than automatically assuming that a low-pressure switch should close
whenever pressure is low. In a pump-down system, a low suction
pressure with the liquid-line solenoid closed is normal during
shutdown.
2
,Question 3
A normally closed high-pressure safety control is installed in series with
a compressor contactor coil. During operation, condenser pressure rises
excessively and the control opens. Which statement best describes the
immediate electrical effect?
A. The compressor contactor coil is de-energized
B. The condenser fan motor is forced to run continuously
C. The liquid-line solenoid opens
D. The evaporator pressure regulator increases its pressure setting
Answer: A. The compressor contactor coil is de-energized
Rationale: A normally closed high-pressure safety control permits the
compressor control circuit to remain energized under normal
conditions. When excessive discharge pressure causes the safety to
open, the circuit to the compressor contactor coil is interrupted. The
contactor drops out, disconnecting power to the compressor motor.
This is a protective function intended to prevent dangerously high
condensing pressure and associated mechanical, thermal, and
electrical stress. The control does not itself regulate condenser
pressure; it interrupts operation when the pressure exceeds its safety
threshold.
Question 4
A technician is troubleshooting a refrigeration control circuit containing
a transformer, thermostat, liquid-line solenoid, low-pressure switch,
high-pressure switch, compressor contactor, and compressor motor. The
compressor does not run. The technician measures proper voltage at the
transformer secondary but finds zero volts across the contactor coil.
What should the technician determine next?
3
, A. Whether the compressor crankcase heater has failed
B. Which series safety or operating control is open
C. Whether the compressor has a low oil level
D. Whether the condenser coil is dirty
Answer: B. Which series safety or operating control is open
Rationale: When a contactor coil has no voltage across it, the first
objective is to determine why the control circuit is not completing the
electrical path. Controls such as thermostats, pressure switches,
overloads, oil-pressure controls, and other safeties may be wired in
series with the coil. A systematic voltage-tracing procedure identifies
the exact point where control voltage is lost. Mechanical compressor
conditions such as oil level or a dirty condenser may cause operational
problems but do not explain the absence of voltage at the contactor
coil unless a related safety has opened.
Question 5
A refrigeration system uses a thermostat with normally open contacts
that close when the controlled space temperature rises above the
setpoint. What happens when the thermostat calls for cooling?
A. The thermostat interrupts the compressor control circuit
B. The thermostat closes its contacts and completes the control circuit
C. The thermostat increases refrigerant pressure mechanically
D. The thermostat closes the high-pressure safety circuit permanently
Answer: B. The thermostat closes its contacts and completes the
control circuit
Rationale: In a conventional cooling control arrangement, a rise in
space temperature above the thermostat's cooling setpoint causes the
thermostat contacts to close. This closure permits control voltage to
pass through the remainder of the circuit and energize the appropriate
4
