Question 1

Which of the following could be the reason that the subcooling would be low on an air conditioning system?

Accepted Answer

A

Question 2

Which of the following would be considered noncondensable gas/es in a refrigeration system?

Accepted Answer

Both nitrogen and air are noncondensable gases in a refrigeration system, meaning they cannot be condensed into a liquid state like the refrigerant. Vaporized refrigerant oil is not a gas, and refrigerant is not considered noncondensable since it can condense back into a liquid state during the refrigeration cycle.

Question 3

If, while troubleshooting an R-410A residential air conditioning system at near design conditions, the operating pressures are found to be 118 psig on the low side and 440 psig on the high side, it is most likely that the system is

Accepted Answer

D

Question 4

Which of the following is NOT a condition of the belt being too tight on a blower?

Accepted Answer

If the belt is too tight on a blower, it can cause bearing damage, excessive noise, and excessive belt breakage. Belt slippage would actually indicate that the belt is too loose, not too tight.

Question 5

Which is NOT a cause for low superheat in an air conditioning system?

Accepted Answer

Low superheat is typically not caused by a refrigerant undercharge. Instead, undercharging would lead to higher superheat because there is less refrigerant available to absorb heat, causing the remaining refrigerant to become superheated. Overfeeding of the metering device, dirty air filters, and restricted airflow through the evaporator coil can all lead to low superheat by causing excessive cooling or reduced heat absorption capacity, which in turn allows the refrigerant to absorb more heat than intended or restricts the amount of heat available to be absorbed.

Question 6

Which type of bearings do most residential fan motors use?

Accepted Answer

Most residential fan motors use sleeve bearings because they are quieter and less expensive than ball bearings. Reed and nylon bearings are uncommon in fan motors.

Question 7

Which of the following is a condition of an air conditioning system that is overcharged?

Accepted Answer

An overcharged air conditioning system leads to reduced evaporator efficiency because the excess refrigerant can cause higher pressure in the evaporator, which reduces its ability to absorb heat effectively.

Question 8

To use the electronic leak detector, the system must contain at least some refrigerant. If the system is operating with a small leak, plenty of pressurized refrigerant is left in the system. But if the system is void of refrigerant, it must first be pressurized with __________, to which a trace of refrigerant has been added.

Accepted Answer

The most commonly used pressurizing gas for leak detection is nitrogen, to which a trace amount of refrigerant is added to make it detectable with the electronic leak detector. Halogen and hydrogen are not used as pressurizing gases, and oxygen is not recommended due to its potential for combustion.

Question 9

If, while troubleshooting a residential central air conditioning system, the technician notices frost on the suction line, what is the most likely problem?

Accepted Answer

Frost on the suction line is a sign that the evaporator coil is freezing up. A dirty air filter can restrict airflow, causing the evaporator to become too cold and freeze up.

Question 10

Which type of leak detection uses a refrigerant additive charged into the refrigeration system?

Accepted Answer

UV leak detection uses a refrigerant additive charged into the refrigeration system, which reacts with ultraviolet light to create a visible glow that can pinpoint the location of a leak. This method is highly effective and efficient, and does not require any special equipment or expertise.

Question 11

Which type of leak detection involves burning refrigerant?

Accepted Answer

Halide leak detection involves a process where the refrigerant, when exposed to a flame, changes the color of the flame, indicating the presence of a refrigerant leak. This method is particularly used for detecting chlorinated refrigerants.

Question 12

If, while troubleshooting an R-22 residential air conditioning system at near design conditions, the operating pressures are found to be 40 psig on the low side and 116 psig on the high side, it is most likely that the system is

Accepted Answer

The operating pressures of 40 psig on the low side and 116 psig on the high side indicate that the system is undercharged. At near design conditions, the operating pressures should be around 68-72 psig on the low side and 250-260 psig on the high side. Overcharging or a dirty condenser would result in higher pressures on both sides of the system.

Question 13

Where is the high-side access port located on most residential central air conditioning systems?

Accepted Answer

The high-side access port is located on the liquid line of most residential central air conditioning systems. The liquid line carries the high-pressure refrigerant from the condenser to the evaporator coil.

Question 14

Which is NOT a cause of high superheat in an air conditioning system?

Accepted Answer

Overfeeding the metering device would lead to low superheat, not high superheat, as it allows too much refrigerant into the evaporator.

Question 15

Which of the following could be the cause for excessive subcooling in an air conditioning system?

Accepted Answer

Excessive subcooling can occur when the system operates in low ambient conditions because the refrigerant condenses more easily, leading to lower temperatures and increased subcooling.

Question 16

Most modern residential blower motors are of which type?

Accepted Answer

Most modern residential blower motors are direct drive, which means they are directly coupled to the blower wheel without the need for a belt. This design is more energy-efficient and requires less maintenance than a belt drive system.

Question 17

Which of the following is NOT a condition of a belt on a blower motor being too loose?

Accepted Answer

The answer of Which of the following is NOT a...

Question 18

Which of the following is a condition of an air conditioning system that is undercharged?

Accepted Answer

An undercharged air conditioning system will have low operating pressures. This means that there is not enough refrigerant in the system to properly cool the air. This can also lead to reduced evaporator superheat, which can cause the compressor to work harder and potentially overheat. However, an undercharged system does not necessarily increase the possibility of floodback to the compressor, and it generally has lower, not higher, operating pressures.

Question 19

If, while troubleshooting an R-22 residential air conditioning system at near design conditions, the operating pressures are found to be 80 psig on the low side and 200 psig on the high side, it is most likely that the system is opperating

Accepted Answer

The answer of If, while troubleshooting an R-22 residential air...

Question 20

Residential air conditioning systems have a superheat range of __________ degrees under normal operating conditions.

Accepted Answer

Residential air conditioning systems typically have a superheat range of 8 to 12 degrees Fahrenheit under normal operating conditions to ensure efficient operation and prevent liquid refrigerant from entering the compressor.

Quiz 21: Mechanical Troubleshooting