0600DB1901

Evaluating Test Results

Variable factors affecting circuit breaker pole resistance include: contact contamination in the form of resistive oxides which develop over time, possible accumulation of particulate contaminants during shipping and storage, and loose terminals or a manufacturing issue with the current path assembly. Each of these contributes to the pole resistance value. Consistent pole resistance values, such as NETA suggests, indicate that the circuit breaker is usable. But also, per NEMA AB-4, “...due to inherent variability in the extremely low resistance of the electrical contacts and connectors....” wide variation in test values do not mean something is wrong. Per both NEMA and NETA it merely means that further investigation is warranted. Review of test method, contact conditioning, load bank testing, and consultation with the manufacturer are good next steps.

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