Tech Tips

As HVAC/R Technicians, we use tools and instruments to take measurements every day. In fact, 90% of our job could not be done efficiently without some kind of measurement.  “How do we measure?” “With what instruments?” “How accurate are these measurements?” These are all questions a thoughtful technician should ask before spending money on a […]

  Image Courtesy of Eaton SNAP ‘N SHIELD Piping support is covered in Section 305 of the IMC (International Mechanical Code). Once again, the IMC isn’t binding, but it is what most local codes are based on. Piping / Tubing Material Maximum Horizontal Distance Between Support Maximum Vertical Distance Between Support Copper Tubing 1 1/4″ […]

We keep two-pole, 40-amp 24v coil contactors on all of our vans. They are versatile and reliable, and you can replace most residential A/C contactors with them. There are a few things to watch for, though, especially when you have a crankcase heater. Many brands power the crankcase heater constantly and shut it on and […]

We have discussed DTD (design temperature difference) quite a bit for air conditioning applications, but what about refrigeration? Let’s start by defining our terms again. Suction Saturation Temperature The saturation temperature is the temperature at which the refrigerant will be at a given pressure if it is currently changing state. This change of state would […]

Most controls and thermostats will have some sort of cycle rate per hour setting that kicks in to prevent over-cycling once the setpoint is reached. These cycle settings don’t kick in until the system starts achieving setpoint, so don’t worry if it will shut off if it’s set to 70° in heat mode and it’s […]

I just noticed this portion of the Carrier air handler sticker for the first time the other day. I’m like most techs; it’s easy for us to ignore the great info posted right in front of us on the data tag. That’s because so many of the notices contain info we are used to seeing. […]

If you work in refrigeration, you may have heard the term “hot pull down.” This phrase describes a condition where the load on the evaporator is above design due to the box temperature or the temperature of the product in the box being higher than it would normally be. My grandpa called me a few […]

Imagine a glass of ice sitting on a table. Now, imagine you place a lid on the glass so that all the water and ice are contained in the glass. If the ice and water are well mixed, the water and ice will both be at 32°F because the ice is slowly changing state from […]

This is the second article in a three-part series where we explore advanced psychrometrics. The source material for each of the articles in this series is ACCA Manual P Sections 3, 4, and 5. This article is based on information found in Section 4. If you followed the previous advanced psychrometrics article, you now know […]