AC Flashcards
The pressure at which the refrigerant changes state from a vapor to liquid
Condensing pressure
The pressure at which the refrigerant changes state from a liquid to vapor
Evaporating pressure
T/F Superheat always refers to a vapor.
T
T/F All liquid must be vaporized for superheating to occur
T
Subcooling always refers to a liquid at a temperature _____ its saturation temperature for a given pressure.
Below
One main function of a compressor
Circulate refrigerant
One function of discharge line
Carry high pressure superheated vapor from compressor discharge valve to condenser
Receiver acts as a ____.
Surge tank
T/F Liquid line transfers low pressure subcooled liquid to metering device.
F high pressure
Meters liquid refrigerant from liquid line to evaporator
Metering device
The metering device is a restriction that separates high pressure side from _____ _____ _____ in refrigerant system.
Low pressure side
The evaporator, like the condenser, acts as a _____ _____.
Heat exchanger
_____ transports low pressure superheated vapor from evaporator to compressor.
Suction line
4 stages of refrigeration cycle
Expansion
Evaporation
Compression
Condensation
Superheat on the systems low side can be divided into 2 types:
Evaporator superheat
Total (compressor) superheat
What controls evaporator superheat?
TXV
Low evaporator loads can be caused by 4 things:
Iced up or dirty coil
Defrost circuit malfunction causing coil icing
End of refrigeration cycle
Low refrigerant charge
When liquid refrigerant enters the compressor crankcase while compressor is running is called _____.
Flooding
Name 2 things could cause slugging to occur?
Bad TXV
Low load
3 metering devices
Thermostatic expansion valve (TXV)
Automatic expansion valve (AXV)
Capillary tube
If the diameter is too small _____,
the evaporator will be starved.
If a capillary tube is over/under charged, it will backup the excess liquid in the condenser causing high/low head pressure.
Over
High
It is extremely important to install a filter drier before the capillary tube to catch any _____ _____.
Foreign objects
3 main functions of TXV
Provide constant amount of evaporator superheat
Keep evaporator full of refrigerant
Prevents flood back of refrigerant to compressor
Color codes
R11
R12
R134A
Blue
Yellow
Blue
Air may enter refrigeration system because of what 3 things?
Tube, gasket or flange leaks
Poor charging procedures
Poor recovery or recycling procedures
2 types of leak detection
Electronic
Ultraviolet (UV) Fluorescent
What 2 things are detrimental to a refrigeration system?
Air
Moisture
New and replacement compressors come shipped with dry nitrogen that needs to be removed and _____ prior to use.
Evacuated
If the contamination from a burned out and or sludged compressor reaches a replacement compressor, the new compressor will probably _____.
Burn out
The oil from a burn out can cause serious skin irritation and possible _____.
Burns
When do you evacuate a compressor?
When it has been isolated from the rest of the system
TEWI
Total Equivalent Warming Impact
CAA
Clean Air Act
The substances affected by the CAA were divided into __ main classes.
2
Section 608 of the CAA prohibited individuals from knowingly _____.
Venting off refrigerant
Recovery and recycling equipment manufactured after November 15, 1993 must be equipped with _____ fittings.
Low-loss
Owners with charges greater than _____ are required to repair substantial leaks.
50 lbs
How many types of EPA technician certifications are there?
4
Why is it necessary to have superheat in a refrigeration system?
To ensure refrigerant is in a vaporized state.
