HVACR Unit 18 - Special Refrigeration Components

What is a desiccant?

substances which are used to remove water from refrigerants

Why do some systems have discharge check valves?

to help in the uni-directional flow of refrigerant

Why are suction-to-liquid line heat exchangers used on refrigeration systems?

to stop liquid returning to the compressor and improves efficiency of the system

What is the function of a receiver in a refrigeration system?

to store excess refrigerant which is not being used

Why is it important to ensure that any refrigeration component used on an HFC 410A system be rated for HFC 410A use?

when different refrigeration pressures are applied on different valves that may be ruptured and damaged

What is the purpose of a solenoid valve?

A solenoid valve is a flow control device which is used to regulate the flow of refrigerant. Generally installed to stop or allow the flow of liquid refrigerant in the liquid line.

What is an evaporator pressure regulator?

An EPR is a refrigerant flow-control device used to control the refrigeration pressure in the evaporator such that it does not operate below a specified minimum value. Usually used on systems with multiple evaporators and placed after the outlet os the evaporator in the suction line.

How does a CPR work?

Crankcase pressure regulator is an outlet pressure regulator. It is present in the suction line just before the compressor and is close-on-rise regulator. Crankcase pressure is the closing force opposed by spring force.

What types of systems normally use crankcase pressure regulators?

Crankcase pressure regulators (CPR) are installed on systems where the crankcase pressure rises above its designed level. Selected based on refrigerant used, refrigeration capacity, design suction pressure, maximum crankcase pressure and pressure drop across the valve.

How does a sight glass moisture indicator indicate the presence of moisture in the system?

It detects if there is any moisture content present in the refrigerant. Moisture is generally detected using a filter paper containing chemical salt. The moisture is sensitive to this filter paper and changes its color. Dry system is green and wet system is wet.

What two ways are desiccants help inside a filter drier?

One method is different desiccant materials are mixed to form solid moulded core. Another method compresses different desiccant beads together inside a shell.

Name three types of system isolation valves.

Stem-type, diaphragm valves, and ball valves

What is the difference between a strainer and filter drier?

Strainers are used to remove the solid particles entering the metering devices. Filter driers remove solid particles and moisture.

Why are filter driers required when installing a new system that uses POE lubricant?

When acid and alcohol are mixed polyester and water are produced. POE lubricant in a new refrigeration system reacts with refrigerant and moisture to form acids.

Why do some manufacturers require that suction-line filters be removed from a system after the system has been cleaned?

When there is more pressure drop it is an indication that the filter is over loaded with contaminants and it is removed.

What are the two main types of relief valves used on a refrigeration system?

automatic and one-time

Explain the operation of a solenoid valve.

close type : if voltage is applied, the plunger opens using internal spring and refrigerant flows through open type: if voltage is applied, the plunger closes and refrigerant flow is stopped

Explain the different methods used to maintain a minimum high-side pressure on outdoor air-cooled condensers.

controlling condenser fan motors : speed control or on-off control OROA pressure regulating valve : open on rise of outlet valve used to control refrigerant flow

What is the function of an oil separator in a refrigeration system?

generally placed in the discharge lines and collect refrigerant oil mixture from the system and direct it to the compressor crankcase

How does a suction-to-liquid heat exchanger improve system efficiency?

increases the subcooling and formation of flash gas in metering device is stopped.

Where are vibration eliminators installed in a system?

made up of braided bronze strips with copper to absorb vibrations usually installed at the inlet and outlet of the compressor

What is the purpose of the three-way valve in a system with a heat-reclaim coil?

placed between the compressor and condenser to redirect the vapor hear discharge by the compressor to the heat reclaim coil and used for heating of domestic hot water

What is the function of a suction line accumulator in a refrigeration system?

prevents liquid refrigerant from returning to the compressor

What is the purpose of a hot gas muffler?

reduce noise from refrigerant being compressed in the compressor