The thermostatic expansion valve regulates refrigerant flow to the evaporator based on
Suction line superheat
The capillary tube is a type of
Metering device
The TXV sensing bulb is mounted
On the suction line between the evaporator and compressor
An external equalizer is used when
The pressure drop across the evaporator is excessive
When the load on the evaporator increases, the TXV
Increases the flow of refrigerant
Superheat is
The sensible heat absorbed by the refrigerant after it has boiled to a vapor
The sensing bulb and transmission tube are a part of the
TXV
A small amount of superheat in the suction line is desirable with a TXV to
Ensure that no liquid refrigerant enters the compressor
The thin metal disc connected to the needle in the TXV is called the
Diaphragm
Liquid refrigerant should be completely boiled to a vapor
Approximately halfway through the evaporator
Balanced port TXV's are used to
Feed refrigerant at a normal rate with low ambient temperatures
The pressure-limiting TXV
Shuts off the refrigerant flow to the evaporator when it has reached a predetermined pressure
The automatic expansion valve was designed to
Meter refrigerant to the evaporator with an electronic sensing device
What force is cancelled out using a balanced-port TXV?
Liquid force
What type of TXV uses a large port for pull-down capacities and a smaller port for holding loads?
Dual port
What type of valve uses a control board, transistors, thermistors, and a stepper motor controlled by an algorithm?
Electronic expansion valve
What is not a pressure, or force acting on a TXV diaphragm?
Head pressure
The needle and seat of a TXV are normally made of____________
Stainless steel
The TXV tries to maintain a constant _________ in the evaporator.
Superheat
What are the four types of charges that the TXV uses to control refrigeration?
Liquid charge, vapor charge, cross liquid charge, cross vapor charge.
What are three factors that determine the capacity of a TXV?
Liquid temp entering TXV, pressure drop across TXV, and evaporating temp.
What is the recommended superheating temp for high temp evaporators?
(30�F) 10 - 12�
What is the recommended superheating temp for medium temp evaporators?
(0 - 30�F) 5 - 10�
What is the recommended superheating temp for low temp evaporators?
(below 0�F) 2 - 5�
At what pressure drop across an air conditioning evaporator would you need and external equalizer?
3 psig
The external equalizer on a TXV is used to _________ for, not getting rid of,________ drops from the inlet to the outlet of the ______
Compensate, pressure, evaporator