First, let’s address some areas of possible confusion

  1. The Word “Condenser” Can Mean two Different Things Many in the industry will refer to the outside unit on a split air conditioner, heat pump or refrigeration unit as a “condenser” even though it will often contain the condenser, compressor, and other parts. It’s better to call the outside component the “condensing unit” or simply the “outside unit” to reduce confusion.
  2. Cold and Hot are Relative terms Cold and Hot are both an experience, a description, a comparison or an emotion. Cold is a way to describe the absence of heat in the same way that dark describes the absence of light. We will often use the words cold and hot to compare two things “Today is colder than yesterday” or to communicate comfort “It feels hot in here”. These are useful communication tools, but they are comparisons not measurements.
  3. Heat and Absolute Zero Can be Measured We can measure heat in BTUs and light in lumens, we cannot measure cold or dark. Absolute cold is the absence of all heat. -460°F(-273.3°C) (cold) is known as absolute zero, -460°F(-273.3°C) is the temperature at which all molecular movement stops. Any temperature above that has a measurable level of heat. While this is a known point at which all molecular movement stops, it has not (and likely cannot) be achieved.
  4. Boiling Isn’t Always Hot When we say it’s “boiling outside” we mean it’s hot outside. This is because when we think of boiling we immediately think of water boiling in a pot at 212°F (100°C) at atmospheric pressure, which is 14.7 PSI (Pounds Per Square Inch)(1.01 bar) at sea level. Boiling is actually just a change of state from liquid to vapor, and the temperature that occurs varies greatly based on the substance being boiled and the pressure around the substance. In an air conditioner or a refrigeration system, refrigerant is designed to boil at a low temperature that corresponds to the design of the system. On an average air conditioning system running under normal conditions with a 75°(23.88°C) indoor temperature, the evaporator coil will contain refrigerant boiling at around 40°F(4.44°C). In air conditioning and refrigeration when we refer to “boiling”, “flashing” or “evaporating of refrigerant” we are talking about the process of absorbing heat, otherwise known as cooling
  5. Cooling and Heating Cannot be “Created” We are not in the business of making heat or creating cool; it cannot be done. We simply move heat from one place to another or change it from one form to another. When we “cool” a room with an air conditioner, we are simply absorbing heat from the air into an evaporator and then moving that heat outside to the condenser where it is “rejected” or moved to the outdoors.
  6. Heat and Temperature Aren’t the Same Imagine a shot glass of water boiling away at 212°F(100°C). Now imagine an entire lake sitting at 50°F(10°C). Which has a higher (hotter) temperature? That answer is obvious-I just told you the shot glass had 212°F(100°C water in it so it is CLEARLY hotter. But, which contains more heat? The answer is the lake. You see, heat is simply energy and energy at its basic form is movement. When we measure heat we are measuring molecular movement; the movement of molecules–atoms stuck together to make water or oxygen or nitrogen. When molecules move FASTER they have a HIGHER temperature and when they move SLOWER they have a LOWER temperature. Temperature is the average speed (velocity) of molecules in a substance, while heat is the total amount of molecular movement in a substance. The lake has more heat because the lake has more water (molecules).
  7. Compressing Something Makes it Get Hotter (Rise in Temperature) When you take something and put pressure on it, it will begin to get hotter. As you pack those molecules that make up whatever you are compressing, they get closer together and they start moving faster. If you drop the pressure the molecules will have more space and will move slower causing the temperature to go down.
  8. Changing the State of Matter Moves Heat Without Changing Temperature When you boil pure water at atmospheric pressure it will always boil at 212°F(100°C). You can add more heat by turning up the burner, but as long as it is changing state (boiling), it will stay at 212°F(100°C). The energy is changing the water from liquid (water) to vapor (steam) and the temperature remains the same. This pressure and temperature at which a substance changes state instead of changing temperature is called its “boiling point”, “condensing temperature” or more generally “saturation” point.
  9. Superheat, Subcool, Boiling, and Saturation Aren’t Complicated If water is boiling at sea level it will be 212°F(100°C). If water is 211°F(99.44°C) at sea level we know it is fully liquid and it is 1°F(-17.22°C) subcooled. If water is 213°F(100.55°C) at sea level we know it is vapor and superheated. If something is fully liquid it will be subcooled, if it is fully vapor it will superheated, and if it is in the process of change (boiling or condensing) it is at saturation.