Quiz 24
If a thermostatic expansion valve's thermal bulb came loose from the suction line at the outlet of the evaporator, which of the following could result?
All of the above are correct
Explain the recommended method of charging a system with a capillary tube system.
Capillary tube is critically charged (contact manufacture for proper charge
As the evaporator load increases, an automatic expansion valve will _________ to reduce the evaporator pressure
Close
T/F: An automatic expansion valve uses a thermal bulb to help control the amount of refrigerant being fed into the evaporator.
False
T/F: As the load on an evaporator increases, the automatic expansion valve will open to allow more refrigerant to enter the evaporator.
False
T/F: The pin or valve port piston of the electronic step-motor expansion valve can move a linear motion of 300 steps per second
False
The two pressures that push to close a thermostatic expansion valve are the ________ pressure and the evaporator pressure
Spring
What two pressures control the operation of an automatic expansion valve?
Suction pressure, evaporator pressure, spring pressure
If the thermal bulb assembly develops a leak, what will occur?
The bulb pressure will reduce and the valve will close
T/F: A capillary tube controls the refrigerant flow into the evaporator
True
T/F: A refrigeration system that continuously runs under high-load conditions (hot pull downs) would most likely use a thermostatic expansion valve with a vapor charged thermal bulb assembly
True
T/F: An AXV works best when the evaporator load is constant
True
T/F: The solid-state controlled expansion valve uses a thermistor as a sensing element to vary the voltage to a heat motor operated valve.
True
T/F: The step-motor valve uses a small motor to control the valve's port, which in turn controls evaporator superheat.
True
T/F: Too high of pressure entering the compressor will cause the density of suction gases entering the compressor to increase
True
When is an external equalizer-type TXV required?
When using refrigerant distributors, and when you need to compensate for the excessive pressure drop
Why should you allow a refrigeration system to operate at least 15 mins before reaching any conclusions?
You want the system to equalize and stable out
The primary function of an expansion device is to _______.
all of the above
The purpose of a capillary tube is to _________.
all of the above
The purpose of an externally equalized thermostatic expansion valve is to _________.
compensate for excessive evaporator pressure drop
A thermostatic expansion valve controls refrigerant flow to the evaporator based on ________.
evaporator suction line superheat
Balanced port TXVs are used to _______.
feed refrigerant at a normal rate with low condenser entering air temperatures
The cross liquid charge bulb at the TXV contains fluid that ________.
has different characteristics from the system fluid
When the load on the evaporator increases, the TXV ______.
increases the flow of refrigerant
The pressure limiting TXV _______.
limits the refrigerant flow rate to the compressor capacity
The TXV sensing bulb is mounted _________.
on the suction line between the evaporator and the compressor
The automatic expansion valve maintains a constant _________
pressure
The TXV maintains a constant ________
superheat
