Neutral Hazards

8/7/2019 Neutral Hazards

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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 beidentified.

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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 openedcreating an arc (ORPS EM-SR-WSRC-FTANK-2005-0009)

A circuit was moved to a different distribution panel, butthe 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 anemergency light that received power from anotherdistribution 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 labels

For the purpose of this presentation, please review the following labels:

Circuit Breaker

Circuit A Ungrounded Conductor

CircuitB

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 accordingto 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 unbalancedload current. (Grounded Conductor)

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CktA

CktB

Click to Lock Out

Circuit BClick to Energize Circuits

The desiredtechnique used to

remove a device Isto cut the neutrallead or disconnectthe device leaving aneutral pigtail. (Click)

The Neutral Will

Remain at Ground

Potential

X

Ckt A

Ckt BCkt A

Ckt B

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CktA

CktB

If You Break TheNeutral 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

AvoidAvoid

Breaking TheBreaking The

Neutral BundleNeutral Bundlein a Multiin a Multi--WireWire

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:

y If known, Lock out both / all load breakers.

y 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:

y Stop work and remove the hazardous condition or plan a new work

package considering known energized conductors.

y 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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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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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 orJerald Kinz

Potential Hazards with

Neutral Conductors

Neutral Hazards

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