Working with refrigerants

After studying this chapter, you will be able to

Purge system with nitrogen. Pressurize system for leak detectionDescribe different methods of leak detection.Explain use of vacuum pumps and evacuation

proceduresUnderstand procedures for charging systems

with refrigerant. Explain recovery and recycle procedures

INERT GASES NITROGEN (N) and

Carbon Dioxide (CO2) ,meaning they do not support combustion. They are high pressure gases used to purge the system while brazing , or pressurize the system for leak detection

Pressure Regulator

Basic Refrigeration Charging method

System charging is adding the proper quantity of refrigerant to refrigeration system so that it operates as intended . Some systems can handle a wider variation of charge size in particular, those with liquid receivers. Direct expansion systems with small condensers and capillary tube expansion devices tend to be very sensitive to refrigerant mass and are said to be Critically charged . In all cases, the system data plate should contain useful information

Charging a refrigeration system depends upon:- Type and size of the system- Available equipment - Requiring accuracy

Method of charging

1. Volumetric charging by graduated cylinder 2. Charging by weight 3. Charging by sight glass 4. Charging according to system performance 5. Electronic charging 6. Vapor refrigerant charging 7. Liquid refrigerant charging

Method of charging

Charging according to system performanceThis done by monitoring the suction pressure, discharge

pressure, evaporator superheat and liquid subcooling out of the condenser

Thermometers are tightly attached to the liquid line and suction line then refrigerant is the gradually added into the system and the pressures and temperatures monitored. As the estimated suction and discharge pressures are approached, and the design subcooling and superheat values are achieved, a suitable charge is achieved. There is a delay between adding refrigerant and the resulting performance being achieved there for these performance should achieved for some time to insure that the reading are more or less constant

Method of charging

Electronic charging machines During larger scale manufacturing, equipment tends

to be charged using electronically controlled charging machines. These generally measure refrigerant into system using precise mass flow meters, and are generally accurate to ±0.5gr