Arkansas HVACR NewsMagazine January 2025

HVACR NewsMagazine January 2025

Tech News

The second measurement is downstream of the coil and in the supply plenum. To make this hole, use a step bit and drill a 3/8" diameter hole in the sheet metal. In this scenario, the measurement is 0.18” WC while the fan is running.

by moving it to get access or recovering the refrigerant in order to remove and clean it. If you're interested in seeing a more detailed step-by-step process for Method 5 , check out this article: https://www.acservicetech.com/post/measu ring-the-static-pressure-drop-across-an evaporator-coil-to-see-if-it-is-clogged If you want to learn more about these 5 methods, watch this video! Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Check out our Inverter Mini Split Heat Pump Book! Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Follow us on Instagram!

Subtract the second measurement from the first to determine the static pressure drop. 0.85” WC - 0.18” WC = 0.67” WC. 0.67” WC is an extremely high pressure drop to have on a system which tells us that there is some sort of blockage on the underside of the coil. This blockage must be removed in order for the system to operate correctly with proper airflow. Normally, the highest pressure drop that a manufacturer may specify are 0.4 or 0.5" WC. However, a typical static pressure drop will usually be between roughly 0.1 0.35” WC. This is a dry pressure drop reading while the outdoor unit is not being powered. Because refrigerant is not cycling through the coil, humidity in the air will not condense onto the coil. A wet coil pressure drop may be roughly .05" WC higher than a dry measurement. Evaporator coil manufacturers list both a dry and wet coil pressure drop in "WC, based on the airflow CFM crossing the coil. Compare the actual "WC pressure drop to the manufacturer's data pressure drop to see if the unit is in spec. If the actual "WC measurement is higher or significantly higher, the underside of the coil needs to be cleaned

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