Tech Tips

Sometimes I beat around the bush too much in these tech tips, so let's get down to the nitty-gritty! (As Nacho Libre would say.) Humidity inside a home should be maintained between 30% and 60% relative humidity. I like to shoot for 50% in humid climates when possible (and by possible, I mean financially feasible […]

HVAC installs sometimes come with surprises. Some of them are good, like when you have a really nice customer who buys you lunch or leaves you a generous tip. But HVAC installs can also come with plenty of bad surprises, like a defective part, not enough space to install the unit, an incorrectly sized platform […]

Often in commercial HVAC and refrigeration, you'll come across a sight glass/moisture indicator on the liquid line. (Oil sight glasses also exist, but those are different from what I'm talking about today.) Sight Glass The sight glass portion is simple; it's just there to show if the liquid line has a full line of liquid […]

DISCLAIMER: HVAC School is NOT an official OSHA safety training resource! Although we provide safety tips in good faith, our website is not a substitute for safety training from an authorized OSHA training source. Locking out and tagging equipment is one of the most basic safety procedures in general industry and maintenance work, especially in […]

Deburring copper tubing (often called reaming) is the practice of running a blade around the inside of tubing after you cut it to remove the burr edge from the inside. It's an important practice and should be performed whenever possible. Deburring reduces turbulence inside the lines, as burrs can cause turbulence.   HOWEVER… YOU MUST […]

This photo is of a blower door test we performed at my own house using a Retrotec blower door. You will notice the 15-passenger van outside the window, which is a dead giveaway. A blower door is used to measure the tightness of a building and is often discussed in terms of an ACH50 number. […]

Testo 557 vacuum gauge and Appion core removal tools shown I've had a change of heart. Back in the early 2000s, during the big construction boom, I did many system startups on residential units for a large company I worked for. When installers ran the line sets prior to startup, they weren't always very careful […]

We already know that oxy-acetylene torches have a lot of safety considerations attached: don’t oil regulator threads, bubble-test your hoses, you get the picture. But there’s one more we haven’t really covered: the 1/7 rule (or 1/10 rule, based on the latest industry guidance).  This commonly cited rule reduces the likelihood of flammable acetone coming […]

When sealing ductwork or repairing HVAC insulation, the tape you choose dictates the long-term integrity of the system. Temperatures fluctuate wildly in attics and mechanical rooms,  and the tape must be able to withstand these environments without degrading. To better understand how different professional-grade adhesives actually perform under elevated temperatures, we decided to put them […]