Ideal Gas Rulebreakers
Breaking the Sound Barrier So, what do you think of when you hear an “ideal gas?” R22, R12 maybe… natural? Take a look at the F-18 above. It’s breaking the sound barrier, and that cloud is a shockwave. It has nothing to do with this article, but I think it’s pretty darn cool! An ideal […]
Read more
Get an EEV Open (Like Magic)
This tech tip comes from our contributor, compressor decapitator, and super tech Ulises Palacios. Many ductless systems and some high-efficiency unitary systems have electronic expansion valves. If you find one that is stuck closed, you may be able to get it open temporarily by putting a strong magnet like the one shown above on the […]
Read more
What Does “Air Free CO” (Carbon Monoxide) Mean?
  Almost everyone knows that CO (carbon monoxide) is really nasty stuff and nothing to play around with. Humans will often begin exhibiting symptoms of CO poisoning at 200 ppm (parts per million) of CO in a space. Studies have also shown that the effects of CO exposure can accumulate over time, resulting in health […]
Read more
Density of Air & Water Part 2
Here is part 2 from Michael Housh from Housh Home Energy in Ohio. Thanks, Michael! This is part two in a series on a deeper look into the sensible heat rate equations. You can find the first article here HERE if you missed it. This article will dive deeper into the density of “standard air” […]
Read more
You’re Grounded
One of the most common questions we get from techs is about using a voltmeter to diagnose a high voltage circuit. It’s especially tricky when a tech is used to working on a low-voltage or 120V circuit, where there is a clear “hot” side of the circuit and a clear “grounded” side of the circuit. […]
Read more
High Capacity Amperage Measurement
We had a situation a few months back where we needed to monitor amperage on a grocery store panel over a period of time. The trouble was that we needed data-logging capability AND accurate measurement at 600+ amps. Finding an all-in-one solution proved to be quite expensive. Luckily, my friend Jim Bergmann happens to own […]
Read more
Pool Heat Pumps, The Basics
Note: My brother Nathan wrote this a few years back, and I only did some minor editing. A pool heat pump is essentially a water-cooled air conditioner in reverse. It usually has a large air evaporator on the outside that looks like a condenser coil and a heat exchanger (usually tube-in-tube) on the inside. A […]
Read more
Troubleshooting Advanced Systems
This article was written by Senior Refrigeration Tech Jeremy Smith. Before we get to it, I want to remind you that ALL of the tech tips are available in chronological order HERE, and you can sort through them alphabetically by selecting the letters and numbers above the tips. It’s a great link to share with […]
Read more
Sensible Heat in Air and Water
Here is another great explanation from Michael Housh of Housh Home Energy in Ohio. Thanks, Michael! I’m going to lay out and compare the sensible heat rate equations for both the air-side and water-side of HVAC to help draw similarities and dive deeper into the science behind these equations. This is the beginning of a […]
Read more

The HVAC School site, podcast, and tech tips are
made possible by generous support from