Metering Devices
A thermostatic expansion valve (TXV) is mechanically designed to maintain what constant metric?
Constant evaporator superheat
Where should a liquid line filter-drier be physically located within a split system layout?
Between the condenser and the metering device
A compressor operating with a broken internal reed valve will display what classic gauge symptoms?
High suction pressure and low discharge pressure
What happens to the system dynamics when a liquid line filter-drier becomes partially clogged?
The refrigerant flow decreases, creating a temperature drop across the drier
What is the most reliable method for permanently removing moisture from a contaminated refrigeration system?
Triple evacuate the system to 500 microns with a deep vacuum pump
An automatic expansion valve (AXV) is strictly designed to maintain what metric constant?
Constant evaporator pressure
What is the primary dual purpose of installing a filter-drier in a system?
To remove moisture and contaminants from the refrigerant
What are the typical pressure symptoms of an air conditioning system operating with a dirty evaporator coil?
Low suction pressure and low discharge pressure
An overcharge of refrigerant in a fixed capillary tube system results in what distinct pressure profile?
High suction pressure and high discharge pressure
When adding refrigerant to an undercharged operating system, how should it be introduced to the low side?
In vapor form
A decrease in sensed system superheat causes the thermostatic expansion valve to respond by doing what?
Closing
Where would a liquid receiver normally be piped into a refrigeration circuit?
It is used to store high-pressure liquid refrigerant downstream of the condenser
An inefficient compressor can be recognized by what combination of operating pressures?
Lower than normal head pressure and higher than normal suction pressure
Non-condensable gases trapped inside a capillary tube air conditioning system will cause what visual symptoms?
High suction pressure and high discharge pressure
When topping off an operating system containing a blended zeotropic refrigerant, how must it be charged?
Introduce the refrigerant as a liquid into the low side using a throttling valve
An automatic expansion valve is best suited for what type of system load profile?
When the system load remains fairly constant
Where would a system sight glass normally be located for optimal viewing?
In the liquid line, before the metering device
While troubleshooting a residential system, a tech finds low operating pressures and low compressor amp draw; what is the likely cause?
Low airflow across the evaporator
When testing a motor capacitor with a multimeter, what reading indicates that the capacitor is completely open?
Infinite resistance / O.L
When joining copper tubing to steel using a torch, what is the recommended brazing filler alloy?
A 45 percent silver alloy
Which of the following operational claims is NOT true regarding a fixed capillary tube metering device?
They maintain a constant evaporator temperature
Which specialized suction-line component is engineered to prevent raw liquid refrigerant from flooding the compressor?
Accumulator
Which of the following system conditions could directly cause a severe liquid floodback condition to the compressor?
Defective expansion valve overfeeding
Which of the following conditions is explicitly NOT a normal symptom of a system running low on refrigerant?
High head pressure
Solid contaminants like sludge and carbon resulting from a severe hermetic motor burnout are best eliminated by doing what?
By flushing the system and then installing filter/driers in both the liquid and suction lines