Arkansas HVACR NewsMagazine January 2025

HVACR NewsMagazine January 2025

Tech News

find out their hose was not depressing the Schrader core fully. So, what should it be? Generally speaking, 10-12°F of subcooling at the outlet of the condenser coil is most common. However, you must look for the proper design subcooling for the particular system you are working on. Some systems will require subcooling readings of up to 16°F for maximum efficiency and capacity.

use a scale WHENEVER adding or removing charge so you can monitor your progress. While it is true that subcooling is the primary charging measurement on a TXV/TEV/EEV system, subcooling is important to check on every system every time you connect (whenever possible). Negative Subcooling isn't possible if the liquid line temperature and pressure are taken at the same point. However, it is possible for your tools to be miscalibrated, which could make zero subcooling look like negative subcooling. Zero Subcooling means that the refrigerant in the liquid line is a mix of liquid and vapor; this is not an acceptable condition EXCEPT in cases where the system is designed to inject discharge gas into the liquid line on purpose to increase liquid pressure (headmaster). Low Subcooling is an indication that not enough refrigerant is contained or “packed” in the condenser. This can be due to undercharge, poor compression, or a metering device that is oversized or failing open (overfeeding).

Many techs will say that subcooling is how you “set a charge” on a TXV/TEV/EEV metering device system. Subcooling is one of many factors you consider when setting a charge, but you first need to ensure that your equipment is properly matched with the correct metering device. The airflow must be set in properly, the blower, air filter, condensing coil, and evaporator coils must be clean, and you must