Life Support Track: HVAC, Cooling, Water and Power · Module 1 of 4 · about 15 min
How refrigeration works
Almost every air conditioner, chiller and fridge uses the vapor-compression cycle. The compressor squeezes refrigerant gas, raising its pressure and temperature. The condenser dumps that heat outside, and the refrigerant turns to liquid. The expansion device drops the pressure, and the evaporator lets the cold refrigerant boil and absorb heat from the space you are cooling. Then it goes back to the compressor.
Technicians read the system with pressures and temperatures. Superheat (how far the gas is above its boiling point leaving the evaporator) and subcooling (how far the liquid is below its condensing point leaving the condenser) tell you about charge and airflow. Guessing the charge by feel is how compressors get killed.
Refrigerants are regulated. Under Section 608 of the Clean Air Act, EPA requires certification to buy and handle many refrigerants and bans knowingly venting them. The certification types are Type I for small appliances, Type II for high-pressure systems, Type III for low-pressure systems and Universal for all three.
Newer refrigerants with lower global warming potential are coming in, and some are mildly flammable. That changes handling, storage and leak checking, so stay current on what you are working with.
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Module quiz
5 questions, 4 correct to pass. You'll see what you missed and why, and you can retake it.