HVAC School

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 a tra...

At Kalos, we had several cases that had us scratching our heads. We knew we had flowed nitrogen while brazing, but we still found copper oxide inside the piping. How could that happen if we were doing what we had been taught?

The missing piece was the purge before the flow. We were putting nitrogen into the pipe, but we had not always given it enough time, at enough...

First off, the correct acronym for a GFI (ground fault interrupter) is “GFCI” (ground fault circuit interrupter). The purpose is to act as a safety device to protect from electrical shock. GFCIs are important components of electrical safety; they even make an appearance in our

It's always good to reaffirm some of the basics of energy, work, and matter. The five rules below are some of the most basic and important.

The First Law of Thermodynamics

States that energy cannot be created or destroyed. It can only change forms or be transferred from one object to another.

If you'd like to learn m...

Condensate overflow prevention devices, or float switches, as they are often called, are such simple devices that you wouldn't think there would be much room for controversy. In my experience, there are few areas of the trade where technician an...