#air flow

Tech Tips:

Replacing Residential HVAC Equipment With “Predictable Results”
By:Adam MufichWhen replacing a furnace or air handler for a customer, there is nothing worse than starting up the equipment and having it sound like the latest SpaceX rocket taking off. You insert your static pressure probes into the duct, and your stomach drops as you read the numbers.  You realize the new high-end system […]
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Impacts of Decreasing Evaporator Airflow
By:Bryan Orr Airflow, airflow, airflow… When we set up and commission comfort cooling and heating systems, we need to pay more attention to airflow before worrying about the fancy controls or the refrigerant circuit. One way to do that is by checking out Bill Spohn's Airflow 101 webinar on ESCO Group's learning network, which you […]
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Low Airflow – Beyond the Obvious
By:Bryan Orr Every now and then, a tech will call me and give me the same story of woe. They're working on a system and have the following readings: Low superheat Low suction pressure Low head pressure They'll reassure me that the system airflow is correct. So, what could possibly be wrong? I'll ask how […]
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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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Underlying Problems That Get Missed
Today, I ran a service call with another tech where the previous tech had diagnosed an intermittent piston restriction. I read the history beforehand. For the past several years, there were many assorted comfort complaints and a lot of minor charge adjustments in both the summer and winter. It is worth noting here that the […]
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How to Determine the Friction Rate for Residential Duct Design
By:Neil Comparetto This article is written by one of the smartest guys I know online, Neil Comparetto. Thanks, Neil! Recently, I posted a question in the HVAC School Group on Facebook that went like this: “When designing a residential duct system, what friction rate do you use?” As of writing this, only one answer was […]
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Podcasts:

Measuring Airflow Podcasts w/ Jim Bergmann
By:Jim BergmannBryan Orr In this two-part podcast series, Jim Bergmann covers measuring airflow in HVAC systems. He covers a wide range of airflow measurement instrumentation and readings. In the HVAC industry, many techs confuse static pressure for airflow. Although you need static pressure to have airflow, it is NOT airflow and can fluctuate rather wildly […]
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Airflow – Latent, Sensible, WB, DB, RH and Static
By:Bryan Orr In this episode, Bryan talks a bit about the air side of the system. Understanding airflow is all about seeing the relationship between readings. We cover latent and sensible heat, relative humidity, wet and dry-bulb temperatures, and static pressure. Latent and sensible heat refer to heat that we can feel (sensible) or heat […]
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