Fluke - Insulation resistance and electrical circuit testing for HVAC compressor motors

HVACR system mechanics rarely rely on a simple test to diagnose the "good" or "bad" condition of a function or process. When approaching a capacitor, they listen carefully, run their hand over the air column being discharged, and then touch the suction, liquid, and discharge lines, a gesture they immediately regret. All this before even opening their toolbox. Next, they attach gauges and graduated thermometers to carry out a more precise diagnosis. The more checks and cross-checks they perform, the more satisfied they are and the closer they get to an accurate diagnosis. Regarding compressors, insulation resistance tests (IRT), as well as refrigerant, oil moisture, and acidity tests, are also proven tests that they now add to their range of skills. An insulation resistance tester provides "non-destructive" DC voltages to the motor windings and insulation points to measure the current leakage rate. There is no perfect insulator. All insulators leak. The question is how much they leak and if the leakage rate varies over time due to insulation breakdown or contamination. This latter point is the key to predictive maintenance.