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Basement Sewage Grinder Pump 20A GFCI Keeps Tripping Issue

GFCI Tripping for Sewage Grinder Pump? Expert Troubleshooting Guide

Grinder pump systems often face GFCI nuisance tripping and motor overload due to electrical faults.

To diagnose excessive amp draw causing GFCI trips, use a clamp meter around the pump’s power cable to measure current. Inspect for grounding faults by testing continuity between ground and neutral wires. Check the pump motor for signs of wear or binding that increase load. Replace the GFCI with a high-quality unit rated for motor loads. Regularly clean and maintain the pump to prevent mechanical strain that raises current draw.

The basement sewage grinder pump's 20A GFCI keeps tripping. Although the GFCI has been replaced, it continues to trip. The electrical panel breaker for this circuit is not tripping. I suspect possible causes could be a grounding issue or that the pump is starting to fail and drawing too much current. The manufacturer's label is no longer present, so I'm unsure of the motor's amp draw. If an overage in amp draw is the main concern, how can I obtain a reading? Is there a type of AC tester that includes an AC adapter for inline insertion, or is an inductive lead used instead? Additionally, if measuring motor current draw is necessary for diagnosis, could you recommend a specific make and model of tester (and leads)? If grounding is a concern, how can I test for that?

To clarify, a GFCI does not measure amps; it only monitors the power on the HOT and NEUTRAL wires. It ensures that the power on the HOT wire matches that on the NEUTRAL wire. If there is an imbalance, such as power leaking to the ground, it will trip.

There are a couple of reasons why the GFCI might keep tripping.

1) GFCIs are sensitive to motors. When a motor starts, it draws a significant amount of power on the HOT wire, resulting in less power on the NEUTRAL wire. This discrepancy can cause the GFCI to trip.

2) If this tripping has recently started, it could indicate a problem with the motor or the wiring connected to it.

The reading I'm getting from the watt/amp meter you suggested shows a low of 144 watts and a high of 1,365 watts (11.8 amps). Is this a typical motor "run" amp draw for an average ejection pump? The label on the pump lid has faded under the previous homeowner. Once the new GFCI trips, it cannot be reset for several hours, sometimes not until the next morning. This issue occurred with the old GFCI as well. The electrical panel breaker never trips. What should be the next diagnostic step to determine if the issue lies in the wiring or the pump?

It seems there might be an issue with the pump itself, especially if it's an older model. The only way to test it would be to use a megger on the unit while it's in the water, but since you don't have that tool and it can be quite expensive for a one-time use, it's not practical.

One possible test you could perform is to check for stray voltage in the fluid. I'm not sure how effective this would be, but it would require your tester to be set to voltage testing mode. Place one probe on the ground wire or a metal screw in the box, and the other probe into the fluid to check for voltage. The unit needs to be powered on to determine if voltage is present.

This is the only other suggestion I can think of. It's based on the fact that the GFCI is detecting power not returning through the neutral wire, similar to how it goes out on the hot wire.