Potential Hazards with Neutral Conductors

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• Neutrals are grounded but carry current under load.

Neutrals Are Current Carrying Conductors

• The source of neutral current cannot always be identified.

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Potential Hazards with Neutral Conductors

• Breaking a neutral under load could create a shock hazard.

• Individuals contacting a lifted neutral potentially provide an alternate path to ground.

• A broken neutral or lifted neutral could result in a shock or an arc.

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Energized Neutral Examples

• A neutral was misidentified and inadvertently opened creating an arc (ORPS EM-SR-WSRC-FTANK-2005-0009)

• A circuit was moved to a different distribution panel, but the neutral was spliced in the original panel (ORPS EM-RL-PHMC-PFP-2005-0011)

• An electrician received a shock after lifting a neutral from its bus bar. The neutral received its power through an emergency light that received power from another distribution panel. (ORPS SC-PNSO-PNNL=PNNLBOPER-2005-0018)

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Configuration That Requires Additional Precautions:

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Notes:

• 3 current carrying conductors in a raceway.

• Copper ground wire omitted for simplicity.

• Highlighted in yellow indicates energized.

Component labelsFor the purpose of this presentation, please review the following labels:

Circuit Breaker

Circuit A Ungrounded Conductor

Circuit B Ungrounded Conductor

Grounded Conductor (Neutral Conductor)

Ground

Ballast / Fluorescent Light

Ballast / Fluorescent Light enclosure

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The Multi-Wire Branch Circuit is an acceptable configuration according

to the National Electrical Code (NEC) Section 210.4.

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This circuit has also been referred to as:

• The Edison Circuit

• Common Neutral Circuit

• Shared Neutral Circuit

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• These circuits are typically found on 120 / 240 volt single phase systems, but can be found on 208Y /120 and 277Y / 480 volt systems as well.

• The Grounded Neutral wire carries the unbalanced load current. (“Grounded Conductor”)

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Ckt A

Ckt B

Click to Lock Out Circuit “B”Click to Energize Circuits

The desired technique used to remove a device Is to cut the neutral lead or disconnect the device leaving a neutral pigtail.

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The Neutral Will Remain at Ground

Potential

X

Ckt A

Ckt BCkt A

Ckt B

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Ckt A

Ckt B

If You Break The Neutral Bundle, It

Will Become Energized From

Circuit “A” (Click)

You May See an Arc when disconnecting

If You Contact The Neutral Conductor You May Feel A

Shock.

X

Avoid Avoid Breaking The Breaking The

Neutral Bundle Neutral Bundle in a Multi-Wire in a Multi-Wire Branch Circuit!Branch Circuit!

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Use the following guidance when the neutral conductor must be interrupted:

• Treat the neutral as energized even though the circuit is locked out at the source. (Use PPE that is appropriate for the hazard, i.e. gloves and eye protection)

• Measure absence of voltage to ground immediately after lifting leads when more than one neutral is lifted from a device or when a splice is broken.

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Use the following guidance when the neutral conductor must be interrupted:

If known, Lock out both / all load breakers.

If both circuit breakers in a multi-wire branch circuit are not known?

o Test the neutral circuit with a clamp-on type current detector to identify if the neutral is carrying current before lifting neutral leads or breaking a neutral connection.

NOTE: Current will exist only if one or more circuits sharing the neutral have a load energized at the time of measurement.

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When a common neutral hazard is discovered at a device:

Stop work and remove the hazardous condition or plan a new work package considering known energized conductors.

It should be corrected by installation of pigtails or other means, to maintain continuity of the neutral wiring in accordance with NFPA 70 National Electrical Code.

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Other general precautions include:

Label the doors of lighting and power panels where common neutrals are known to exist. This will alert LOTO planners and workers of potential problems.

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Other general precautions include:

Provide instructions in work packages where common neutrals are known to exist to remind workers to be alert to wiring that may indicate a common neutral and to maintain neutral circuit continuity.

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Other general precautions include:

Suspect a multi-wire branch circuit when three or more neutral conductors are spliced together in a junction box, outlet box, or lighting fixture.

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Questions or Comments?Contact Bobby Gray or Jerald Kinz

Potential Hazards with Neutral Conductors