Refrigeration Basics with Elliot and Bert Part 2

Part 1 is available at https://www.youtube.com/watch?v=eKb_xbADAgA&ab_channel=HVACSchool.

There are four main components in the typical refrigeration circuit: an evaporator, a compressor, a condenser, and a metering device. Each of these components manipulates the pressure or temperature of the refrigerant inside it. For example, the metering device drops the pressure of liquid refrigerant going into the evaporator; when this happens, a small temperature change occurs, and the pressure drop also causes some of the high-pressure liquid refrigerant to boil off. The components are connected by the suction, discharge, liquid, and sometimes expansion lines.

Matter comes in three phases: solid, liquid, and vapor. We should never see solid refrigerant in an HVAC system, but the refrigerant changes between the liquid and vapor states; evaporators transform liquid refrigerant to vapor, and condensers transform vapor refrigerant back to liquid.

These phase changes usually occur at specific temperatures, but we can manipulate the pressure to raise or lower the boiling point. That’s why we can have cool vapor and warm liquid with roughly the same amount of energy despite the temperature differences. Saturation temperature is the temperature at which the refrigerant either boils or condenses, and it varies based on pressure.

The suction pressure is the pressure of the cool, low-pressure vapor refrigerant in the suction line. Its pressure should be the same from start to finish, and we can take the pressure reading at the suction service port. A common rule of thumb is that the suction saturation temperature should be about 35 degrees below the indoor ambient temperature, give or take about 5 degrees.

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