Quiz 1 Ch 19, 20, 21
A sensing bulb that contains two substances: one is a noncondensing gas and the other is a solid.
Adsorption gas cross-charged
Which of the following statements regarding oil level regulators is false?
As the oil level drops in a compressor, its regulator returns oil to the compressor.
Which of the following statements about splash lubrication systems is false?
Clearances between moving parts in this type of system must be greater than in pressure systems.
Attaches the piston to the crankshaft.
Connecting rod
A shaft section that is larger and has a different center from the rest of the shaft.
Eccentric
What attribute of vibration absorbers allows them to reduce vibrations?
Flexibility
A sensing bulb charged with a refrigerant that is different from that in the system and which is completely vaporized at the desired temperature.
Gas-charged
A sensing bulb charged with the same refrigerant as the system and which is completely vaporized at a predetermined temperature.
Gas-charged
A sensing bulb charged with a different refrigerant than what is in the system, and some of it is always in a liquid state.
Liquid cross-charged
Why should refrigerant entering a compressor be all vapor and not liquid?
Liquid slugging can damage the compressor.
A sensing bulb charged with the same refrigerant as the system, some of which is always in a liquid state.
Liquid-charged
Moves up and down in the cylinder to draw in, compress, and discharge the refrigerant vapor.
Piston
Connect pistons to connecting rods.
Piston pin
Creates a seal between the piston and the cylinder wall.
Piston ring
To best eliminate vibrations, which part of a vibration absorber should be fastened to a wall?
Side farthest from the compressor
If an AXV is undercapacity for its application, what will happen?
The evaporator will be starved.
Which of the following best describes the way fully hermetic compressors are lubricated?
They are lubricated by oil circulating with the refrigerant.
Located between the cylinder head and cylinder block.
Valve plate
Th e main purpose of a metering device's orifice is to produce _____.
a pressure drop
When a thin layer of fluid adheres to a solid, but the two substances are not mixed together, _____ occurs.
absorption
When two substances are mixed and become one substance, _____ occurs.
adsorption
Capillary tube failure will most likely occur when it is _____.
bent or crimped
A compressor must start while under load if an automatic expansion valve does not have a(n) _____.
bleeder or bypass
On systems with small-diameter horizontal suction lines, the sensing bulb should be mounted on the _____ of the suction line.
bottom
In rotating-vane compressors, the vanes may be brought into contact with the cylinder walls by spring pressure or by _____.
centrifugal force
Devices that specifically provide overcurrent protection for compressors are ______.
circuit breakers and fuses
The Scotch yoke type of reciprocating compressor does not use _____.
connecting rods
To prevent liquid refrigerant slugging and oil slugging on compressors that operate in low ambient temperature, equip it with a(n) _____.
crankcase heater
To maintain a constant pressure in the evaporator when the system is running, an AXV _____ when evaporator pressure begins to increase.
decreases refrigerant flow
A crankcase heater provides heat to a compressor from ______.
electric heating elements
Automatic expansion valve operation is based on its sensing bulb.
false
Before installing a vibration absorber, stretch, twist, and compress it to prepare it for leakproof operation.
false
An HVACR system can be designed to use a lower torque compressor motor if the TXV is equipped with a(n) _____.
pressure limiter
If the moving parts within a compressor are not lubricated, it will most likely ______.
produce small metal chips that will damage the system
Capillary tubes are used extensively in _____ systems.
refrigerator and window ac unit
Adding refrigerant and lubricant, checking pressure, and other procedures require the use of _____.
service valves
An HVACR muffler uses a _____ to reduce noise caused by gas pulsations.
set of baffles
A(n) _____ prevents refrigerant leaks around the shaft of an open-drive compressor.
shaft seal
In scroll compressors, refrigerant typically enters the scrolls from the _____ and exits out the _____.
sides; center
During normal operation, many modern EEV controllers are able to use _____ as inputs to govern valve position and operation.
temperature and pressure measurements
A thermal overload protects a compressor from overheating by opening ______.
the compressor's power circuit
A crankcase pressure regulator protects a compressor from high pressure in ______.
the low side of the system
Before a sensing bulb is installed, use steel wool to clean _____.
the sensing bulb and suction line
An expansion valve assembly with a faulty valve or seat could allow refrigerant to leak during the Off cycle and allow liquid refrigerant to flow into the suction line.
true
Because modulating metering devices can change refrigerant flow based on load, they operate more efficiently than fixed metering devices.
true
By using an external equalizer, a TXV is able to provide the correct refrigerant flow, even when there are large pressure drops through the evaporator.
true
Extra refrigerant in a system using a capillary tube will cause the compressor motor to work harder during start-up.
true
Since altitude can affect atmospheric pressure, an AXV needs to be adjusted to account for this.
true
A low-side float system maintains a constant level of liquid refrigerant in the _____.
evaporator
The best superheat setting for an evaporator, called the minimum _____ signal (MSS) setting, is the point that causes the least sensing bulb temperature change while the system is running.
stable
If the superheat setting is increased to correct for an oversized TXV orifice, the evaporator will be _____ much of the time.
starved
The condition in which liquid refrigerant is present in only part of the evaporator is called _____.
starving
An AXV that is overcapacity may allow too much refrigerant into the evaporator and may cause condensation on the _____.
suction line
For increased system efficiency, a capillary tube is usually positioned so that a portion of it is in contact with the _____.
suction line
A sensing bulb must not be affected by the air or liquid being cooled. It should be wrapped in insulation so that only _____ affects the bulb.
suction line temperature
A discharge line thermostat turns off a compressor if ______ gets too high.
discharge line temperature
When a TXV is feeding refrigerant into an evaporator with multiple circuits, a(n) _____ should be installed.
distributor
An EEV controls its orifi ce using a(n) _____.
electric operator
If the pressure in a sensing bulb is _____ the combined pressure from the evaporator and the spring, a TXV's valve is forced open.
equal to
A crankcase heater is used to protect a compressor from ______.
excess oil slugging
A direct-drive compressor generally turns at a different speed from its motor.
false
An oil level regulator captures oil as it flows through screens, baffles, filters, or certain piping arrangements within it.
false
Due to its method of compression, a screw compressor does not provide discharge pressure that is as smooth or pulsation-free as that of a reciprocating compressor.
false
If the pulley on an open-drive compressor has a diameter three times greater than the pulley on the drive motor, the compressor shaft will rotate three times faster than the motor shaft.
false
In a scroll compressor, refrigerant vapor is compressed between two spinning scrolls.
false
The higher the temperature in a low-side float (LSF) flooded system, the lower the low-side pressure.
false
The limited amount of refrigerant allowed to pass through a metering device into the evaporator is at a high pressure.
false
The shells of fully hermetic compressors are typically bolted together
false
Compressor parts that are bolted together usually contain _____ to prevent leaks.
gaskets
A discharge line pressure switch turns off the compressor if ______ gets too high.
head pressure
Piston-type metering orifices are most often used on _____ systems.
heat pump
When capillary tube systems cycle off , _____.
high-side and low-side pressures equalize
A PWM solenoid EEV controls its valve opening by _____.
holding the solenoid valve in an open position in discrete increments
In a centrifugal compressor, the spinning _____ flings refrigerant outward, compressing it against the casing.
impeller
A system equipped with a pilot-controlled thermostatic expansion valve is likely to be a _____.
large, high-capacity system (50 tons and over)
When a capillary tube is replaced, it is good practice to also replace the _____.
liquid line filter-drier
The primary purpose of an accumulator is to protect a compressor from ______.
liquid refrigerant
The primary purpose of an AXV is to maintain constant _____.
low-side pressure
The primary purpose of refrigerant oil is to ______.
lubricate the mechanical parts of a compressor
A TXV is operating properly when the evaporator is filled _____.
mostly with liquid
An advantage of capillary tubes over modulating metering devices is that capillary tubes have no _____.
moving parts
A(n) _____ ring helps to lubricate the cylinder wall and prevent excess lubricant from entering the cylinder.
oil
In evaporators equipped with a pan float design, the suction tube extends to the bottom of the pan to ensure that _____ collected in the pan is drawn into the suction line and recirculated.
oil
An internal unloader is typically operated by _____.
oil pressure controlled by a solenoid valve
The adjusting nut or screw on a thermostatic expansion valve is sensitive and should not be turned more than _____ turn while the unit is operating.
one full
A controller modulates the EEV through the use of an algorithm to maintain the desired _____.
superheat
For a TXV adjusted to its MSS point, increasing spring tension on a TXV's adjustment screw will result in an increase of _____.
superheat
The main value that influences the operation of a TXV is _____.
superheat
If the orifice of a TXV is oversized, too much refrigerant will pass into the evaporator and cause the suction line to _____ before the sensing bulb can close the valve.
sweat or frost
In a low-side float-operated control system, the liquid refrigerant is at a low temperature and will absorb considerable heat in both the On and the Off cycles.
true
Once all of the refrigerant in a gas cross-charged sensing bulb is vaporized, the valve is at its maximum operating pressure.
true
Several fixed-orifice metering devices are often supplied by manufacturers for air conditioners that may need on-site changes to suction line length.
true
The oil that circulates in the compressor removes much of the heat from the compressor and motor in hermetic units.
true
The outer diameter of a piston ring is larger than the diameter of the cylinder.
true
The proper TXV and evaporator combination should keep surging and hunting to a minimum but still permit full evaporator use.
true
The rate of flow through fixed metering devices is relatively constant when the compressor is running.
true
The refrigerant charge in systems using capillary tubes is critical.
true
Some HVACR systems require special TXVs to accommodate _____.
variations in operating conditions, high system capacities, & multiple evaporators
A measure of an oil's ability to flow at given temperatures is its _____.
viscosity
