Refrigeration, Metering Devices In Capacity Controls, Chapter 23 Book 2 Flashcards
Hand operated expansion valve 
Seldom used in modern refrigeration systems occasionally used in bypass lines around the automatic control valve and can be used in case of control valve failure
Automatic expansion valve, or constant pressure valve
An adjustable spring exerts a downward force on a diaphragm evaporator pressure pushes on the other side of the diaphragm. The spring is adjusted so the right amount of refrigerant enters the evaporator once the  condenser shuts off the pressure in the evaporator rises, and it pushes harder on the diaphragm closing the valve. Once the compressor starts again, the valve is opened due to the evaporator pressure being drawn out by the compressor. This valve cannot be used when more than one cooling coil is connected to the same compressor.
Thermostatic expansion valve
Most widely used refrigerant control, very similar to automatic expansion valve except it has a thermal power element that is usually charged with the same refrigerant that is used in the system and is strapped to the piping evaporator outlet as the bulbs senses temperature change the pressure in the bulb changes and adjust the valve this requires a vapor to leave their operator slightly super heated, are usually 5 to 6°C if there is large pressure drop across the evaporator, a equalizing line can be used to connect the underside of the diaphragm or bellows with the outlet of the evaporator
Low pressure float valve
In the flood evaporator, it is used to maintain a constant level of liquid. Refrigerant gets its name because it is located on the low pressure side of the system may be installed directly in the evaporator or in accumulator usually has a bypass line with a head operator expansion valve. If the pump should fill, cooling can be maintained by the expansion valve, bypassing the pump.
High pressure float valve
Gets its name because it is located on the high-pressure side there’s
No extra refrigerant. It flows directly from the condenser into the high pressure, float valve valve, controls liquid, refrigerant into the evaporator at the same rate as vapor is drawn from the evaporator. The refrigerant charge in the system is critical to much because liquid to carry over into the compressor to Lil will reduce the capacity of the system 
Capillary tube
Is the simplest of all refrigerant flow controls it’s a fix the length of tubing with a very small inside diameter. It is used to restrict the flow of the liquid from the condenser to the evaporator and maintain the pressure difference between these units often soldered to the discharge of the evaporator, where the superheated vapor flows.
Evaporator capacity control, sectional evaporators
Basically, this divides the evaporator into sections, each section has its own full control valve or expansion valve. The sections will be turned on and off with the load demand.
Evaporator dampers
Either face or bypass damper, the face damper covers the whole operator and adjust airflow over the evaporator depending on load the bypass damper has a phase section over the evaporator and a bypass section so that when the face section is closed, the bypass suction is open so the airflow to the room is not interrupted
Three types of primary operating controls
Temperature pressure and humidity temperature is thermostats pressure is pressure starting humidity is humidistat
Method that is not used to control the refrigeration, compressor output
Thermodynamic expansion valve
To compensate for large pressure drop in an evaporator the thermal expansion valve is equipped with an equalizing line which connects to the underside of the diaphragm or Bellows with the?
Outlet of the evaporator instead of the inlet
Refrigeration system using a high-pressure float provides for storage of the refrigerant in the?
Evaporator
