Hot Pull Down and What it Means
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 […]
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Air Flow and Ice – A Thought Experiment
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 […]
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Coil SHR, Ventilation, and Bypass Factor – Advanced Psychrometrics Part 2
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 […]
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Refrigerants, Flammable & Toxic
There has never been a more complicated and confusing time surrounding refrigerants than what we are in right now. We are seeing flammable HC (hydrocarbon) refrigerants with increasing regularity, and EPA rules that just changed appear to be changing again. With all this tumultuous change, it's important to know what to look for in refrigerants […]
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Room Sensible Heat & CFM – Advanced Psychrometrics Part 1
This is the first of a three-part series of articles that will dive deep into advanced psychrometrics. The source material for each of these articles may be found in ACCA Manual P Sections 3, 4, and 5. This article is based on information found in Section 3.  Psychrometrics is the study of the physical and […]
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Watts So Confusing?
Most motors are designed to a set amount of work, usually rated in either watts or horsepower (746 watts per HP). Watt's law states that watts = volts x amps. If a particular motor needs to do 1 horsepower of work at 120 volts, it will draw about 6.22 amps. And yes, in an inductive […]
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Why HEPA is a Great IAQ Option
I am like most contractors and techs. I've heard about HEPA for a long time, but I never looked into how it could be integrated into an A/C IAQ strategy until now. First, here's what HEPA is: HEPA (High-Efficiency Particle Arrestance) is an ASME, U.S. DOE standard that specifies a capture rate of 99.97% of […]
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How to Use a Manufacturer Fan Table and Why They are Important
Many installers and service technicians know how to read and use a manufacturer fan table, but this is a quick review with a few extra tips for newer techs. It’s also a good reminder to senior technicians about how this easy-to-use practice can also be easily abused. At installation, properly setting up airflow is imperative to the […]
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7 Horribly Challenging Ways To Transform Your Business
Business isn’t easy. Generally, when I look back at how much work it has taken to get a business off the ground, I wonder what I would have done if I had known what I know now. I wonder if I still would have been willing to put in all that work all over again. […]
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