Tech Tips

A few times in the past, we’ve heard the phrase “the house is the biggest duct” because of the way air moves through it. Well, we can take it a step further and see that there are similarities that go just beyond air movement.  A building has several layers to keep things like moisture, heat, […]

Delta T is the difference in temperature between two points of the same medium. It is commonly used by scientists and engineers to analyze the amount of heat transfer in a system. In general HVAC terms, it is the measurable change in temperature between an air input and air output. However, it could also be […]

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. Many things may deter people from working in the HVAC industry. Perhaps surprisingly, exposure to heights could be the deal-breaker. (Not […]

You may have noticed that 3/8″ liquid lines are generally the norm in equipment 5 tons and under. We went to a job where the system had a 1/2″ liquid line, and it got me thinking about the ramifications of going larger or smaller on the liquid line. Liquid Line Basics The liquid line should […]

In residential, most techs and installers size the suction (vapor) and liquid lines to the stubs on the equipment. In larger built-up systems, sizing the piping is rarely the responsibility of the technician. But what happens if we show up to a job where the lines cannot be (reasonably) replaced because the size is different? […]

Air changes per hour (ACH/ACPH) simply describes how many times the total quantity of air in a room (or structure) is completely replaced per hour. If you have a 10'x10'x10′ room, the room contains 1000 cubic feet of air. If the supply and return to the room provide a balanced 100 CFM (cubic feet per […]

This tech tip comes from a post in the HVAC School Facebook group by Ed Janowiak. Ed is the Manager of HVAC Design Education at ACCA, a longtime friend of HVAC School, and an educator who does a lot of great work for the industry. Thanks, Ed! This past Thursday, I taught a class where […]

Fenestration is a fancy architectural term that means “openings in the outside of the building.” You will see this word a lot when you read ACCA Manual J or when you are doing a Manual J load calculation. Fenestration loads include heat losses and gains through windows, doors, skylights, etc., and they can make up […]

Photo Courtesy of Parker/Sporlan There are many brands and styles of evaporator pressure regulating valves (EPR), but none as common as the Parker/Sporlan SORIT and ORIT valves. The diagram above clearly shows some of the common applications. An EPR or “hold back” valve maintains a set suction line pressure and, therefore, coil temperature. That is […]