How Well Do You Know Your Refrigeration System?

By: Peter Kirtschej, Service Advisor, ABR Wholesalers, Inc.

Ever think about what really happens inside a refrigeration system?  Understanding what happens inside the refrigeration system helps us better understand how to service and maintain the systems for optimal performance. 

Let’s start with the heart of the refrigeration system – the compressor.  The compressor compresses a low pressure superheated gas into a high pressure superheated gas.  Super heat refers to heat added to a gas past saturation pressure temperature. The Freon is now a high temperature superheated gas that is pumped into the condenser coil. As the outside air gets pulled through the condensing coil by the condenser fan motor, heat is extracted from the Freon and the Freon changes state to a high temperature high pressure liquid. The Freon continues to flow to the evaporator coil.

Another important component of a refrigeration system is the filter line drier.  A filter line drier should be installed before the metering device.  Filter line driers are important because they have a desiccant inside them.  Desiccant is a material or substance used as a drying agent that soaks up the moisture and particles in the refrigeration system. We all know moisture is terrible to a refrigeration system, so every installation should utilize a filter drier.

Next in line is the metering device.  The metering device controls the amount of refrigerant flow that is enters the evaporator.  This allows for more control of the super heating at the outlet of the evaporator coil.  There are two types of metering devices that can be used – a fixed orifice and a thermal expansion valve.  The TXV (thermal expansion valve) uses a sensing bulb that is strapped to the suction line at the outlet of the evaporator with like refrigerant inside to open the valve against spring pressure inside the valve body.  As the temperature in the bulb increases, so does the pressure on the spring which causes the valve to throttle open.  As the temperature inside the bulb decreases, so does the pressure on the spring which causes the valve to throttle closed.  A fixed orifice or piston is a preselected (fixed) size metering device that is matched based on evaporator and condenser size.  This is usually preselected by the manufacturer or installer.

Once the refrigerant passes thru the metering device, the refrigerant is now a low temperature low pressure liquid.  As this liquid passes thru the evaporator coil, the blower motor circulates the conditioned space return air through the evaporator coil.  As warm air passes through the coil, it is being cooled by the liquid refrigerant.  At this point, the Freon inside the coil is changing state again to a low temperature low pressure super heated gas. This happens because of temperature difference and causes the coil to sweat.  The condensation drains in a drain pan which then drains to either a floor drain or a condensate pump.  As the Freon leaves the evaporator it is sucked back in to the compressor to start the refrigeration cycle again. 

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