LTE 105 MidTerm Review
What percentage of moisture and particles must be removed from reclaimed refrigerants?
100%
Calculate the tare weight of a cylinder if its total weight is 590 lb and the weight of refrigerant in the cylinder is 450 lb
140 lb
What is the sueprheat of a system if the refrigerant temperature in the suction line is 58 degrees F, its pressure in the evaporator is 60 psig, and its temperature in the evaporator is 34 degrees F
24 degrees F
A gauge should not be exposed to pressure greater than__ of its full-scale range for more than a few minutes
75%
What is the maximum amount of refrigerant that a recovery cylinder should contain?
80% water capacity by weight
All refrigerant cylinders should be secured with __ whey they are being transported
A Chain
Halogens cause the torch of a flame to turn__ when they are brought into contact with heated copper
Green
Because they cannot be mixed with mineral oils, __ refrigerants use synthetic oils for lubrication
HFC
According to the ASHRAE classification for refrigerants, the classification for the least toxic and least flammable refrigerant is
A1
A vapor refrigerant is superheated if its temperature is__ the refrigerant's boiling point
Above
Low-pressure refrigerant has the potential to __ heat
Absorb
If the valve system is turned counterclockwise as far as possible, the service vale is in the __ position
Back Seated
Due to their high ozone depletion potential, __ refrigerants were targeted first for phase out by the Montreal Protocol
CFC
During push-pull liquid recovery, vapor refrigerant is pulled from the __
Compressor
A suction service valve connects to the suction line and directly onto the
Compressor at its inlet
To determine a system's subcooling value, the liquid line temperature should be subtracted from the __ temperaturew
Condenser
Subcooling refers to the amount of __ removed from a refrigerant after is has condensed
Sensible Heat
A pressure-temperature curve shows that pressure and temperature are __ in a refrigeration system
Directly Related
All refrigeration systems must have accumulators to operate safely
FAlse
Disposable cylinders are designed to be used for refrigerant recovery
FAlse
To release refrigerant dissolved in compressor oil, an oxyacetylene torch should be used to heat the compressor
FAlse
A decrease in temperature can cause the pressure in a cylinder to increase
False
A gauge that reads absolute pressure should be adjusted depending on the elevation.
False
A liquid line filter drier is installed int he low side of the system
False
A reciprocating compressor uses one or more pistons that move in only one direction
False
A superheated vapor contains some refrigerant in liquid form
False
Active recovery uses an HVACR system's compressor to pump refrigerant into a recovery cylinder
False
CArbon dioxide is classified as an organic refrigegrant(600 series)
False
Cylinder color-coding is a requirement for manufacturers, so technicians do not need to check labels.
False
Electronic leak detectors can only be used to detect CFC's
False
HCFC's have an ODP rating of 0
False
HFC's were the first type of refrigerant to be produced
False
Longer vacuum pump service lines are more effective at pulling a vacuum than shorter service lines
False
Refrigerant in the form of low-pressure vapor has the highest capacity to absorb heat
False
Refrigerant is reclaimed on the job site
False
Refrigeration systems that use capillary tubes as refrigerant metering devices must have a liquid receiver in order to work properly
False
Service Valves are front seated for normal system operation
False
Service technicians can safely use formulas and tables to mix their own azeotropic refrigerant blends
False
Suction lines are generally smaller in diameter than liquid lines
False
The amount of refrigerant that a cylinder can safely hold is 90% of the volume of water that it can hold
False
The refrigerant charge in a system with a fixed orifice metering device should be checked by subcooling
False
The refrigerant temperature in the evaporator is the same as the evaporator temperature when the unit is running
False
Two-part epoxy resins must be heated in order to harden
False
PAssive recovery is generally used on larger systems
Fasle
Both valves need to be closed on a gauge manifold in order to evacuate a system.
Flase
The instantaneous evaporation of liquid refrigerant when it enters the evaporator is called the __
Flash Gas
The separation of the individual refrigerants in a zeotropic blend during phase change is known as __
Fractionation
Two-part epoxy resin kits usually include one tube filled with epoxy and another tube filled with a _
Hardener
Which of the following is not a type of metering device used to control the flow of refrigerant
Hermetic float
Heat is rejected out of a refrigeration system on the __ side of the system
High
Which type of gauge is designed to read pressure values on a single continuous scale and be used on the high side of a system?
High-pressure gauge
During normal operation, refrigerant pumped int o a condenser is in the form of
High-pressure vapor
If the entire refrigerant charge has leaked out of a system, then a __ should be used to pressurize the system to test for leaks
Inert gas
If a refrigerant belongs to the 700 series in the refrigerant numbering system, then it is
Inorganic
A suction line should be __ to prevent moisture in the air from condensing on the cold tubing
Insulated
Many recover cylinders use a __ as a safety device to turn off the recovery machine when the cylinder is 80% full
Liquid level switch
A compressor is designed to draw in __ refrigerant from the evaporator
Low-pressure Vapor
When charging a system with refrigerant, the technician should put the low- and high-side service valves in __
Mid-position
Drawing an extremely low pressure in a refrigeration system is necessary to remove__ from the system
Moisture
How many times can an expendable refrigerant be used?
Once
Pressure that is greater than atmospheric pressure is referred to as __ pressure
Positive
The lowest temperature at which a lubricant will flow is called the
Pour Paint
The process of pumping a systems entire refrigerant charge in tot he liquid receiver is called __
Pump-down
Which zeotropic refrigerant blend is used as a replacement for R-22 in air-conditioning applications, but operates at a higher temperature and pressure?
R-410A
Refrigerant_ is the process of removing refrigerant from a system and storing it in a cylinder
Recovery
Which type of refrigerant cylinder is gray on the bottom and yellow on the top
Recovery
A bourdon tube __ as pressure inside it increases
Straightens
If heat is added to a saturated vapor and raises the vapor's temperature above its boiling point, the heat is referred to as
Superheat
The fins on an evaporator increase the __ of the evaporator tubing, allowing increase heat transfer from the air to the tubing
Surface area
When a refrigeration unit is off, the temperature of the condenser is __ the temperature of the refrigerant.
The Same as
Which evacuation method involves charging a system with nitrogen to absorb moisture?
Triple evacuation
A higher coefficient of performance means that a refrigerant produces its refrigeration effect more efficiently
True
A refrigerant blend containing an HCFC and CFC is considered a CFC
True
A refrigeration system reaches operational balance when the number of vapor molecules that condense into liquid equals the number of vapor molecules that the compressor pumps in to the condenser
True
A small amount of oil circulating throughout a refrigeration system is generally considered acceptable
True
A system should have low-pressure flowing nitrogen within before a leak is fixed by brazing
True
Each time a recovery-recycling machine is used, the filter-drier should be changed
True
Fluids that are used to boil and absorb heat are called refrigerants
True
In a zeotropic refrigerant blend, the refrigerant wit the the lowest boiling point boils first
True
Push-pull liquid recovery should not be used in systems with less than 5 lb of refrigerant charge
True
R-134A has been used a is a replacement refrigerant for systems that use R-12
True
R-22 and R-123 are classified as HCFC refrigerants
True
Recovery cylinders are often equipped with two valves: one for vapor and one for liquid
True
Refrigerant must be recovered from a leaking system before repairs can be performed
True
The liquid receiver service valve ( king valve) should be front seated in order to perform a pump-down
True
The pressure of a perfect vacuum is 29.92 in . Hg
True
VApor recovery must be used in combination with liquid recovery to recover a systems entire refrigerant charge
True
Zeotropic refrigerant blends should be charged as a liquid
True
Vacuum pump oil turns __ when it is contaminated by water
White and Foamy
The cylinder color code for R-134a is
sky blue