Causes of Inconsistent Voltage On a Circuit

Why is there inconsistent voltage on a lighting circuit? Possible causes of a Light Circuit with Incorrect Voltage.

Inconsistent Voltage with a Light Circuit
Electrical Question: Why is there inconsistent voltage on a lighting circuit?

Voltage Problems with a Lighting Circuit

Rex asks:

• I wonder if you can help me understand what is going on with my lighting circuit. I was in the process of replacing a ceiling light and according to my non-contact voltage detector was unable to turn it off.
• I thought first that the 3-way switch was wired wrong but found that it is wired correctly. then, with my multi meter, I tested the voltage between hot and neutral in both switch positions and found something strange: on = 122v, off = 40v.
• There are other lights powered from this junction box so I tested them also (supply hot to circuit hot) and found: a=122v, b=104v, c=104v, d=82v. the switch leg I was dealing with measured 12v and 23v between leg to neutral with the main power disconnected. do you know what could be causing these strange voltages?
• I found no continuity between the neutrals and grounds. I also isolated each wire and verified where they go.

Dave’s Reply:

Thanks for your electrical wiring question Rex.

Incorrect Voltage on a Light Circuit

Application: Incorrect Voltage a Ceiling Light.
Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrical Contractor, or Certified Electrician.
Electrical Tools Required: Basic Electricians Pouch Hand Tools, Voltage Tester, and appropriate Safety Gear.
Estimated Time: Depends on the personal level experience, ability to work with tools, install electrical circuit wiring, and the available access to the project area.
Electrical Safety: Identify the electrical power source to the Ceiling Light, turn it OFF and Tag with a Note before working with the electrical wiring.
Electrical Wiring Parts and Materials: Electrical parts and materials for the Ceiling Light should be approved for the specific project and compliant with local and national electrical codes.
Electrical Codes and Inspections: Installing or changing home electrical wiring should be done according to local and national electrical codes as adopted in your specific area of New York. A permit and inspections may also be required.

Incorrect Voltage in a Kitchen Light Circuit

This electrical wiring project is about Incorrect Voltage in a Ceiling Light Circuit in the Kitchen of an Old Home.

• Great Question Rex!
• From the information you have provided, let’s take a look at a few possibilities that may be contributing to this electrical problem that you have discovered:

Light Circuit with Incorrect Voltage

Light Fixture Components

• It is possible that the inconsistent voltage readings may be caused due to various light fixture types, light fixture control switches, types of LED light bulbs that are installed, or low voltage power supplies for the light fixtures.
• Keep in mind that LED type lights typically operate with a built in electronic power supply.
• Electronic power supplies produce various problems with AC electrical circuits including electrical line disturbances, and they can produce dirty electrical noise conditions on the main power lines.

Improperly Configured Multi-Wired Circuits

• It is also possible that there are multi-wired circuits in the home that are not wired correctly, or that neutral wiring within the home has not been properly configured, or a combination of these two inconsistencies.
• As you can imagine, this is not something that a homeowner can fix, and to be quite honest, some electricians may not know how to track down and fix these problems. However there are some highly knowledgeable electricians that can take care of this for you, but you may have to ask them specifically if they know how to detect and repair incorrect wiring of multi-wired circuits.
• Correcting this problem will involve performing a some electrical tests and measurements with the circuit wiring at each panel located at the home, and then tracking down the problem areas at specific locations of electrical boxes, and then making the required changes in the electrical wiring connections.
• Additional electrical circuit wiring may also need to be installed depending on the extent of the circuit wiring problems that are discovered.

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