Ch 53

When a system experiences reduced evaporator efficiency, ____.

All of the above. the air filters may be dirty and clogged, reducing airflow ice and frost formation may be blocking airflow and insulating the refrigerant an accumulation of dust on evaporator fins and tubing may be reducing heat transfer

Which of the following statements regarding flake ice machines is false?

Flake ice machines have fewer mechanical parts than cube ice machines.

Which of the following statements is not indicative of an inefficient compressor?

High-side pressure will be higher than normal and low-side pressure will be lower than normal.

Which of the following statements regarding a system with a restriction in its TXV is false?

Liquid refrigerant will flood the evaporator and result in low superheat.

Which of the following statements regarding a system with a restriction in its capillary tube is false?

None of the above.

Which of the following statements regarding the effects of moisture in a refrigeration system is false?

Sufficient moisture may separate from the refrigerant and leave the system through the condensate drain.

Which of the following statements about an overcharged refrigeration system using a capillary tube as its refrigerant metering device is false?

Superheat will be high.

When a system with a TXV experiences reduced evaporator efficiency, the ____.

TXV will react to the reduced heat absorption by trying to maintain normal superheat

Which of the following statements regarding the liquid line in a commercial refrigeration system is false?

Vapor and oil should flow freely in the liquid line

A hissing sound at the refrigerant metering device usually indicates ____.

a lack of refrigerant

An undercharged TXV system is likely to have ____.

a lower than normal condenser temperature bubbles in its sight glass Correct! Both A and B.

If a system that uses a capillary tube as its refrigerant metering device has high superheat and insufficient refrigeration while running continuously, the likely cause is ____.

an undercharge of refrigerant

Flake ice machines rely on a(n) ____ to cut ice flakes from solid ice.

auger

Noncondensables trapped in the condenser of a TXV system will ____.

cause the suction pressure and head pressure to be higher than normal

Acidic or contaminated oil removed from a system may be an early indication of ____.

compressor failure

When there is a low-side restriction, ____.

conditioned space temperature will be higher than normal Correct! All of the above. condenser temperature and head pressure will be below normal the cause may be a clogged suction line filter-drier

An anti-short cycle control prevents a compressor from ____.

cycling on before a preset time has passed after shutdown

If gauges must be connected to a critically charged ice machine, ____.

ensure that there is the least amount of tubing or hose between the access port and the gauge as possible

A filter-drier becomes cooler as it absorbs moisture from refrigerant.

false

A sight glass is a sure-fire method of evaluating a system's refrigerant charge.

false

In an overcharged system using a TXV as its refrigerant metering device, the subcooling will be lower than normal.

false

Noncondensables in a refrigerant circuit require the compressor to pump the vapor to a lower temperature and pressure.

false

To perform an ice machine capacity check, the technician should ____.

first turn off and lock out the ice machine empty the machine's storage bin and clean the bin drain Correct Answer All of the above. visually inspect the machine for noticeable problems beforehand

If the water circuit of an ice machine's water-cooled condenser has a thin layer of mineral deposits, the ice machine should be ____.

flushed with scale remover through the water circuit

If an ice machine with a water-cooled condenser has an operating head pressure below normal but still within the manufacturer's recommended range, ____.

heat transfer between the high-side refrigerant and cooling water is efficient and optimal

A commercial refrigeration system with an air-cooled condenser and a capillary tube restriction is running continuously, producing little or no cooling, and experiencing high head pressure. The high head pressure may be due to ____.

high ambient temperatures or reduced airflow through the condenser an overcharge of refrigerant, especially if it is a critically charged system Correct! All of the above. a thick coating of dirt and grime on the condenser

In an overcharged system using a TXV as its refrigerant metering device, the excess refrigerant creates ____ pressure on the high side.

higher

In an overcharged system using a capillary tube, the excess refrigerant creates ____ pressure throughout the system.

higher

A lack of refrigerant causes a(n) ____ sound at the refrigerant metering device.

hissing

Noncondensables trapped in a capillary tube system _____.

increase head pressure

If a commercial refrigeration system with a restriction in its TXV needs to be brought back into operation quickly, the expansion valve can be flushed using ____.

liquid refrigerant

A restriction on the low side of a refrigeration system will ____.

reduce the evaporator's cooling capacity

When necessary, a commercial refrigeration system's refrigerant charge can be checked by monitoring ____.

suction pressure, head pressure, and the sight glass

If a condenser is undersized or dirty, ____.

the dirt or film on the fins and tubing act as an insulator

When a system with a capillary tube as its refrigerant metering device experiences reduced evaporator efficiency, ____.

the subcooling should remain normal as long as the refrigerant charge is adequate there will be no or low superheat because less heat is being absorbed Correct! All of the above. the suction pressure and the evaporator temperature will be lower than normal

Some refrigerant vapor is most likely to pass through the refrigerant metering device into the evaporator when ____.

the system is undercharged

If the water circuit of an ice machine's condenser has a thick layer of scale, ____.

the water valve will open wider to try to compensate for the reduced heat transfer Correct Answer Both A and B. head pressure will rise above the recommended range of operation

If a refrigeration system does not run, __

there may be electrical trouble if the compressor motor is hot there may be a short in the motor windings Correct! Any of the above. an internal overload switch may be open

A water-cooled condenser may need to be replaced due to severe scale buildup inside.

true

In an overcharged system with a TXV, the ability to cool the conditioned space will be reduced.

true

Internal overload safety devices in a motor or compressor will reset after the motor cools.

true

Low or no cooling in a refrigeration system may be caused by an inefficient compressor.

true

Noncondensables are foreign substances that can enter a refrigeration system but do not phase change along with refrigerant.

true

When a TXV cannot fully close, the evaporator will flood during the Off cycle.

true

When a compressor runs continuously, a system may be producing too much refrigeration.

true

When dehydrating moisture-laden refrigerant in a system, it may be necessary to replace the filter-drier several times to remove a sufficient amount of moisture

true

When there is a restriction in the high side, superheat will be high.

true