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 […]

The Four Ps of IAQ I’m not the first, second, or probably even the thirty-second person to write about improving indoor air quality problems using the four Ps approach. It’s a well-known thought process in the building science community—not sure if that’s the case in HVAC circles. The first P is for pollutants. In this […]

John Dalton was an English chemist and physicist born in 1766. He was born into a Quaker family of tradesmen, though he and his brother became teachers early in life. His family bought a Quaker school in Kendal, where he and his brother taught around 60 students.  Dalton separated from the church as a young […]