3Compressors Usually belt driven from the engine Usually have an electromagnetic clutch to turn on/offTwo refrigerant linessuction (larger) draws low pressure, low temp vapor from evaporatordischarge (smaller) lets out high pressure, high temp vapor to the condenser
4Compressor main functions Raise the pressure of the refrigerantWhen compressed the refrigerant temperature rises (no heat is added by the compressor)Important for proper heat transferCreate low pressure in the evaporatorAllows refrigerant to vaporize (boil) absorbing large amounts of heatCirculate refrigerant and oil
23Oil Loss External leak System recovered in a recovery machine Refrigerant caries out oilSystem recovered in a recovery machineMeasure and reinstallComponent replacementOil can be trapped in the old componentHybrid uses dielectric oil
26Key points Heat moves to less warm Heat transfer quickly with large differencesFins increase surface area to dissipate heatCooling effect causes refrigerant to change states from high psi vapor to high psi subcooled liquidMust keep clean and fins straight for proper air flow
28Receiver-Drier Liquid refrigerant from the condenser enters FiltersRemoves moistureStores excessPickup tube ensures that only liquid exits (properly charged system)Desiccant is hygroscopic (absorbs moisture)Different for R-12 and 134aMoisture reacts with refrigerant to form hydrochloric acid.
30Drier Location and Mounting Located in a cool dry placeDesiccant can absorb more moisture when it is less warmMounted verticallyPickup tube in the bottom to only take liquidMounted horizontallyJD uses a side pick-up tubeMake sure “top”
31Sight Glass R-12 A-normal, B-bubbles, C-oil streaking Bubbles usually indicate a loss of refrigerant, streaking usually indicates no refrigerant.