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 […]

Recommended Duct Velocities (FPM) Duct Type Residential Commercial / Institutional Industrial Main Ducts 700 – 900 1000 – 1300 1200 – 1800 Branch Ducts 500 – 700 600 – 900 800 – 1000   As service technicians, we are often expected to understand a bit about design to diagnose a problem fully. Duct velocity has many […]

You may have noticed that 3/8 liquid lines are generally the norm in equipment 5 tons and under. We went to a job recently 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 […]