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Electrical Wire and Cable

Fix a Wiring Problem that Causes Electrical Trouble

Should a white neutral wire have voltage when the circuit breaker is off? A multiwire circuit has been improperly installed, which is causing electrical problems within the home.

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House Wiring Problem
Electrical Question: Should a white neutral wire have voltage when the circuit breaker is off?

My electrical wiring project involves wiring in the Basement of a Old Home.

house wiring problem

This electrical wiring question came from Jeff, a Handyman in Madison, Wisconsin.

Dave’s Reply:
Thanks for your electrical wiring question Jeff.

How a Wiring Problem Causes Electrical Troubles

Application: Electric Multiwire Circuit Wiring Problem.
Skill Level: Intermediate to Advanced – This electrical project is 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 , 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 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 Madison, Wisconsin. A permit and inspections may also be required.

How to Correct a Multiwire Circuit Problem

This electrical wiring project is about a Problem with the Electric Wiring in an Old Home.

As described in this question, a multiwire circuit has been improperly installed, which is causing electrical problems within the home and with devices connected to the faulty wiring.

Multiwire Circuit
What has been described with this question is a Multiwire Circuit, which is where two circuits from different poles share the same neutral wire. Type-NM Cable commonly used in house wiring would be 14/3, and 12/3, where each cable contains a ground wire, white neutral wire, a black wire, and a red wire.

Electrical Codes for Multiwire Circuits
In order for the Multiwire circuit to work properly it must be installed and configured according to the applicable NEC, National Electrical Codes. The following is an example of NEC Electrical Codes that apply to Multiwire circuits:
NEC Article 100 states that the power conductors must originate from opposite poles.
NEC Article 210.4B states that the circuit breakers where the multiwire circuit power wires are attaches must have a tie bar or single handle.

Repairing a Multiwire Circuit Problem
The appropriate repairs to correct this type of problem would include inspecting the circuit breakers in the panel where the multiwire circuit originates, and make the corrections so that the right type of breakers have been installed in the right configuration. For example: Install a two pole circuit breaker with a tie bar. The important purpose of the tie bar is to prevent an energized neutral wire in the event that only a one pole circuit breaker is off, while the other one pole breaker is on. Because the neutral wire is shared between the multiwire circuits the neutral wire will be energized if one breaker is left on.
If it is found that there are more than one sources of power to any part of a circuit, or any device that is attached to a circuit, such as described with the door bell transformer, then the circuit wiring that provides power to the device will need to be examined to identify the duplicate power source so that the wiring configuration may be configured properly for only one power source.

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