Air Conditioning Systems
Master Tech on 29 Jun, 2019 20:08 in HVAC Systems
In order to be able to diagnose or repair any Air Conditioning system, first we must go over how it operates. Over the course of this topic we will elaborate on how the basic A/C system works, Components and operation, different variations of A/C systems (including Orifice Tube & TXV designs)The theory behind Refrigerant operation - how it changes state, vapor to liquid and back to vapor to create cooling.Air Conditioning systems operate on the principal of heat and cooling. Without dragging this topic on extensively, we'll keep it a bit more simple. The Compressor is used to create a high pressure side of the system, drawing in low pressure refrigerant vapor, compressing it to a working pressure of about 150-175psi, depending on conditions and other considerations, as the vapor passes through the compressor the molecules compress creating heat. Hot, high pressure refrigerant vapor then flows to the Condenser, which mounts in front of the Radiator. An electric fan is activated drawing cool air past the Condenser, which causes the Refrigerant to Condense, changing it's state from a high press vapor, to a high press liquid. Liquid exiting the condenser flows to the systems restriction which, is either a TXV or Orifice Tube design, causes a reaction when a high pressure is forced through an orifice. Passing through the orifice creates the low pressure, while the Refrigerant boils at this time. Low Pressure Liquid travels to the Evaporator within the vehicles HVAC plenum (Air box within the dash) As it passes through the Evaporator it changes state once again back to a vapor due to warm/hot air within the plenum and vehicle interior crossing the Evaporator fins.Since it is critical to not have any liquid refrigerant entering the compressor, due to the concept that liquid cannot be compressed, damage to the compressor will occur. In an Orifice tube system any remaining liquid is stored in the Accumulator and vaporized over time. The Accumulator also contains the system desiccant which is critical to keep moisture out of the system, moisture causes freezing within the cool temperatures of the Evaporator. TXV's will not be discussed in this topic as it adds much complexity to the most basic A/C system. If questions regarding a TXV system appear it will be discussed as needed.