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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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 orJerald Kinz
Potential Hazards with
Neutral Conductors