Fundamentals & Science

It’s always good to reaffirm some of the basics of energy, work, and matter. The five rules below are some of the most basic and important. The First Law of Thermodynamics States that energy cannot be created or destroyed. It can only change forms or be transferred from one object to another. If you’d like […]

If you went to school and learned the “gas laws” early on, you probably thought it seemed LAME. Then, later, things like mass flow rates, airflow conversions, and compression ratios seemed HARD. Well… It’s because HVAC is hard if you don’t understand the concepts behind the gas laws, even if you never learn to do […]

The amount of pressure you’re under depends on where you live. I live in Florida, so I’m very close to sea level. Therefore, the weight of the atmosphere is exerting exactly 14.7 pounds per square inch (PSIA) of pressure on every surface in every direction. There is no such thing as negative pressure—only pressure lower […]

Maintaining the correct vapor-liquid refrigerant balance is crucial for air conditioning and refrigeration system performance. Longer line sets hold more refrigerant, which increases the risk of liquid accumulating in the suction line or entering the compressor during off-cycles. Heat pumps are one common application that requires additional measures. Refrigerant flow reverses during heating, turning the […]

Low pressures are often measured in inches of water column or “WC. Like most units of measure, it has a very simple origin; in a water manometer, 1″ of water column is literally the amount of force it takes to raise the column of water by 1”. While some water manometers (water tubes) are still […]

Troubleshooting and commissioning are entirely data-dependent processes. How can you know that a system is undercharged unless you measure the superheat and subcooling? How can you know how much static pressure a blower motor has to overcome? In both cases, we use tools and measurements to help us determine the next steps. However, using the […]

So, what is thermometry anyway? Thermometry is the scientific study of measuring temperature and has roots that date back to as early as 220 BC. During this time, Philo of Byzantium began to study the effects that temperature had on air. Specifically, he observed expansion and contraction caused by temperature change. He did this using […]

We’ve all heard some version of the phrase “heat rises,” but is that really true? First, we need to remember that heat is energy, not matter. Heat is a force, not a thing. So, while heat may result in changes to matter (stuff), it isn’t matter itself. When we add heat to stuff, the molecules […]

As we often do in these tech tips, we will start with the common and more practical explanation of saturation and then move to the more technical and nerdy explanation later. When we say “at saturation” or “saturated” in the HVAC/R trade, we are generally referring to the refrigerant that is in the process of […]