Tech Tips

I once heard someone say, and I have since repeated many times, that BTUs ride on the back of cubic feet of air (CFM). As I've learned more, I've come to the conclusion that the weight or mass of the air passing over the evaporator coil is far more important to understand both in terms […]

Callbacks are horrible. They kill the trade from every possible angle. They destroy customer satisfaction and reduce technician morale by causing long hours, resulting in unprofitability for companies and overall less earning opportunity for everyone. Possibly worse of all, callbacks tell customers that you are no better than their cousin the maintenance man, or worse, […]

In HVAC/R, we are in the business of moving BTUs of heat, and we move BTUs via pounds of refrigerant. The more pounds we move, the more BTUs we move. In a single-stage HVAC/R compressor, the compression chamber maintains the same volume no matter the compression ratio. The thing that changes is the number of […]

A commonly taught method for measuring airflow is the temperature rise method, where you use a heat source that produces a set number of BTU/h, such as heat strips. Then, using the sensible heat air equation, you can “easily” calculate the CFM being produced by the equipment. Let's use this specific example to illustrate the […]

That picture above is a WWII poster reminding soldiers of informed self-interest, which is something we ought to consider when making decisions. We live in a world where we often make decisions quickly and expect to see quick results. That works whenever I buy from Amazon. I order a new belt, and it shows up […]

I walked into my first real job interview in the HVAC trade. The manager was a guy named Ernie, and he walked me out to the warehouse. Quick warning: guys named Ernie are tough. Don't mess with a dude named Ernie. He walked up to a box, snatched a pen out of his shirt pocket, […]

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 […]

There is a big move in residential and light commercial HVAC toward measuring static pressure regularly during commissioning, service, and maintenance. Don't get me wrong… Measuring static pressure is VERY important. The challenge comes in when techs begin taking measurements without understanding where to take them or what they mean. Or worse, they use measurements […]

Sometimes, we can focus on the more complicated aspects of a system and parts installation—like evacuation and flowing nitrogen—and forget the simple and critical common-sense steps to keep contaminants out of the system. One of these is pre-cleaning the tubing and connection before cutting or unsweating. For example, if you are replacing a coil, use […]