Why is it called single-phase 240 when there are two opposing phases (or legs)? I wondered why we called two 120v opposing legs “single-phase 240” for years. Then someone pointed out to me that a typical “single-phase” pole transformer only has one power leg entering and two coming out. That freaked me out. How can […]

This article is part 4 of a 5-part series on troubleshooting by Senior Refrigeration and HVAC tech Jeremy Smith Ok, so we've got our data scribbled and scratched out on paper. Maybe a bit of grease, dirt, and oil, too, if you're doing things right—blood if you're doing it wrong. Now, time to take a […]

A while back, I had a tech who was having some trouble finding a 35 PSI (2.41 bar) make-on-fall pressure switch. One adjustable switch in the catalog said (SPDT), but he didn't quite understand what that meant. In that case, it means single-pole, double-throw, and the “double-throw” part means that the switch has terminals in both the […]