Troubleshooting Cooling
Troubleshooting Cooling
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Question 1 |
The refrigerant entering the expansion device is a _____.
A | cool, low-pressure vapor |
B | hot, high-pressure vapor |
C | cold, low-pressure liquid/vapor mix |
D | warm, high-pressure liquid |
Question 2 |
In a properly operating air-cooled condenser, all of the refrigerant has usually condensed into a
liquid after traveling about _____ of the way through the condenser.
A | 1/2 |
B | 3/4 |
C | 1/3 |
D | 1/4 |
Question 3 |
In most residential split air conditioning systems, the _____.
A | compressor must always be running before the indoor fan can run |
B | outdoor fan motor must always be running before the compressor can run |
C | compressor cannot run unless the indoor fan is running |
D | outdoor fan motor runs whenever the compressor runs |
Question 4 |
While troubleshooting a problem where the compressor will not run, you measure line voltage on
the load side of the energized compressor contactor. If the correct voltage is present, you know the
problem is in the _____.
A | compressor or compressor start circuit components |
B | control transformer |
C | room thermostat |
D | compressor control circuit |
Question 5 |
The Y (yellow) terminal of a standard heat-cool thermostat usually provides power to the _____.
A | 24V control circuit |
B | heating control circuits |
C | cooling control circuits |
D | fan circuits |
Question 6 |
When troubleshooting a cooling problem in a cooling/gas heat system, you place a jumper across
the R (red) and G (green) terminals of the heat-cool thermostat. You do this to find out if the fault is
in the thermostat or the _____.
A | outdoor fan control circuit |
B | compressor control circuits |
C | indoor fan control circuit |
D | furnace burner control circuits |
Question 7 |
If there is a noncondensible such as air or water in a system, it will result in _____.
A | low head pressure |
B | high head pressure |
C | low subcooling |
D | high suction pressure |
Question 8 |
Applying a capacitance boost to a stuck PSC compressor involves temporarily installing a _____.
A | run capacitor in series with the existing run capacitor |
B | start capacitor in parallel with the existing run capacitor |
C | start capacitor in series with the existing run capacitor |
D | run capacitor in parallel with the existing run capacitor |
Question 9 |
When troubleshooting a cooling problem, you find that the discharge (head) pressure is low. Also,
bubbles are observed in the system sightglass. The likely cause of the problem is _____.
A | an undercharge of refrigerant |
B | an overcharge of refrigerant |
C | bad compressor valves |
D | a dirty or restricted condenser |
Question 10 |
If a cooling system has a dirty evaporator coil, the result will be _____.
A | high suction pressure and high superheat |
B | high suction pressure and low superheat |
C | low suction pressure and low superheat |
D | low suction pressure and high superheat |
Question 11 |
When troubleshooting a cooling system, you find that the discharge (head) pressure is higher than
normal. This can indicate _____.
A | an undercharge of refrigerant |
B | a restricted evaporator |
C | a dirty or restricted condenser |
D | low evaporator air flow |
Question 12 |
Slugging in the compressor can be an indication of _____.
A | low refrigerant charge |
B | slugs of oil trapped in the liquid line |
C | insufficient charge of oil |
D | liquid refrigerant in the compressor |
Question 13 |
When troubleshooting a cooling system, you determine that the superheat is high as a result of the
evaporator coil being starved of refrigerant. This problem can be caused by _____.
A | a light system load |
B | an oversized thermostatic expansion valve |
C | a partial loss of charge in the expansion valve power element |
D | the thermostatic expansion valve sticking open |
Question 14 |
When troubleshooting a newly installed cooling system for a low-capacity problem, you should
suspect the cause of the problem is _____.
A | low outdoor ambient temperature |
B | a plugged filter-drier |
C | thermostatic expansion valve bulb leaking |
D | an overcharge of refrigerant |
Question 15 |
The first step when troubleshooting a problem suspected to be a faulty TXV is to measure _____.
A | the system suction and discharge pressures |
B | subcooling |
C | the pressure differential between the input and output ports of the TXV |
D | superheat |
Question 16 |
The difference in sensible temperature between the evaporator inlet and outlet in a typical R-22
system is _____.
A | 50°F to 60°F |
B | 25°F to 35°F |
C | 10°F to 15°F |
D | 80°F to 100°F |
Question 17 |
As a refrigerant flows through the liquid line _____.
A | it does not change |
B | it flashes into a liquid-vapor mixture |
C | it loses latent heat |
D | its sensible temperature decreases |
Question 18 |
If a system with a reciprocating compressor has low discharge pressure and high suction pressure,
the likely cause is a(n) _____.
A | internal compressor problem |
B | loose TXV bulb |
C | dirty air filter |
D | obstruction in the condenser air flow |
Question 19 |
Which of the following symptoms will be exhibited by a fixed-orifice system that is undercharged?
A | High subcooling |
B | High suction pressure |
C | Low discharge pressure |
D | High superheat |
Question 20 |
If frost is seen on the liquid line, it most likely indicates a(n) _____.
A | oversized metering piston |
B | dirty condensing coil |
C | defective compressor |
D | restriction in the liquid line |
Question 21 |
The difference in pressure between the input and output sides of an expansion device in a typical
R-22 cooling system is about _____ psig.
A | 230 |
B | 150 |
C | 50 |
D | 10 |
Question 22 |
If a cooling-only system is calling for cooling and the compressor runs, but the outdoor fan does
not run, the most likely cause is a defective _____.
A | thermostat |
B | compressor contactor |
C | outdoor fan motor |
D | fan relay |
Question 23 |
If a compressor continually cycles off on the high-pressure switch, which of the following is not a
likely cause?
A | Noncondensibles in the system |
B | A faulty run capacitor |
C | A refrigerant overcharge |
D | A condenser fan failure |
Question 24 |
Which of the following TXV problems is likely to cause a flooded evaporator?
A | Excessive system load |
B | Long refrigerant line |
C | Loose sensing bulb |
D | Refrigerant undercharge |
Question 25 |
If a compressor draws 20A during normal running conditions, its locked rotor current is likely to be
_____.
A | 30A to 40A |
B | 50A to 60A |
C | 80A to 120A |
D | 40A to 50A |
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