Testo 760 Category IV Multimeter I was standing at a booth at the HVAC Excellence Educators conference, and an instructor walks up, grabs a meter, and asks me, “What's the difference between a category 3 and a category 4 meter?” Well, I really wasn't sure, but I knew that the category 4 meter is rated […]

This tip comes from market refrigeration and controls technician Kevin Compass. Thanks, Kevin! A little tip when changing liquid cores: If you start pumping them down, begin bypassing discharge gas into the shell to warm it up, push out the remaining liquid, and bring the shell above the dew point so that it doesn't sweat […]

  The second law of thermodynamics puts the first law into context and establishes entropy as a concept. We can simply define entropy as a state of disorder that can only increase or remain the same in natural processes. Processes in which entropy remains the same are reversible, but ones that result in an entropy […]