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What to do about Stray Electrical Voltage Readings

By Dave Rongey - Summary:

How to Identify the Source of Stray Voltage: Stray Electrical Voltage Readings Should be Identified and Corrected Right Away – Stray voltage is not normal and may originate from a faulty electrical or electronic component that could potentially become a serious shock hazard and cause damage to equipment.

Sources of Stray Electrical Voltage

Electrical Troubleshooting Question: I have a single jet water pump motor, 120volt, on my inside spa that was wired by a licensed electrician 10 years ago. It has a dedicated circuit with a GFCI circuit breaker.

This home electrical repairs question came from: Bob, from Las Vegas, Nevada.

Additional Comments: This is a great reference site and I have it in my favorites, but I currently have an unusual situation not covered.

Dave’s Reply:
Thanks for your electrical troubleshooting question Bob.

How to Identify the Source of Stray Voltage

Bob, the indication of problems with the pump motor would be an indication and possible source of the voltage readings, however because the GFCI protection is not tripping this leads me to question the home ground system, please read on.

Skill Level: Intermediate to Advanced – Licensed Electrical Contractor, Not Recommended for Homeowners.
Tools Required: Electricians Pouch of Hand Tools.
Estimated Time: Depends on the extent of the project, the grounding method to be inspected and available access to the project area.
Precaution: If the only ground source for the electrical system will be modified or repaired then the electrical service should be shut off until the new ground source can be reconnected.
Notice: Making changes to the Electrical Service Panel and Ground Electrode System should be done with a permit and be inspected.

Stray Electrical Voltage Readings Should be Identified and Corrected Right Away

This Procedure will help Locate the Source of Stray Voltage

Pin Point the Stray Voltage Produced by Equipment or Connected Circuit Devices

Potential Sources of Stray Voltage

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2 Responses to “What to do about Stray Electrical Voltage Readings”
  1. Dave Rongey says:

    Hi Matt,
    This kind of electrical troubleshooting is always fun. I’m wondering if the house fan has been working fine before the new wiring has been installed and your description of the occurrence? With that question in mind, I would place the circuit breakers back to the original configuration and test the house fan for proper operation.
    Another test to perform to see if there are two circuits that are possibly looped together can be identified by turning off all of the circuit breakers with the exception of the main breaker, then turn on one circuit at a time and see if there is voltage on the wire terminal of any other circuit breaker that is in the off position. If this happens to show up then one of the two circuits must be taken off of the circuit breaker. This condition where two circuit breakers that feed one circuit will not trip the breakers when the circuit breaker’s power source comes from the same main buss, otherwise if each were on the opposing buss there would be a direct short.

  2. Matt says:

    I recently installed two new circuits to my home 220 breaker panel to feed a new bonus room I’m building. One new circuit for will be for the lights, and the other new circuit will be for the outlets. Both new circuits are 20 amps with 12 gauge wire. In the breaker box I replaced two existing one-inch single pole 15 amp breaker switches with a one-inch dual switch 15 amp tandem breaker, thus giving me room to install a new one-inch dual switch 20 amp breaker tandem for the two new circuits.
    Yesterday I turned the new light circuit on and then turned the lights to the new room on and when I did a house fan with an electronic on/off switch (as opposed to a mechanical switch) that is plugged into an outlet on a completely different circuit on a different floor and on a different end of the house turned on “a little” – the fan rotated at about 10% of normal RPM. None of the new wiring goes close to the fan’s circuit until at the breaker panel where the fan’s circuit (single pole 1-inch single switch 20 amp) is located adjacent to the new twin one-inch 20 amp breaker switch I installed (next to laterally, not above and not below). The fan’s breaker switch was in the panel when I bought the house. The new twin 20 amp switch I purchased last week brand new from the store and is designed for my panel box.
    The fan on the other circuit only turns on when the lights in the new room are turned on. My guess is that I have an insulation problem between the two adjacent breaker switches, but I would like a second opinion and hopefully ideas on remedies.
    I appreciate your help!