Relays can be used for many different control applications, including controlling fans, blowers, other relays, or contactors, valves, dampers, pumps, and much more. A 90-340 is a very common, versatile relay that many techs have on their truck. So, we will use it as an example. A relay is just a remotely controlled switch that […]

Let's take a deeper dive into the magic that is gas defrost. Most techs who are familiar with heat pumps understand the basics of a gas defrost. When we apply this strategy to a larger system where we're only reversing a small part of the system, we need to add some controls and valves to […]

Probably the most popular measurement method for indirect airflow readings is total external static pressure (TESP). A dual-port manometer or two Bluetooth single-port manometers are essential to the HVAC technician toolbag. Here’s a quick review of TESP, why it’s important, and how to make the measurements. TESP is a pressure reading of the “balloon” pressure […]