ELECTRICAL SAFETY
CARE & MAINTENANCE OF
ELECTRICAL PANEL BOARDS
Electrical panel boards are essential to distribute
electrical power throughout our buildings and facilities, and they need to be
properly maintained and protected to ensure they operate safely. There are many
factors that can affect the operation of electrical panel boards and associated
circuit breakers, such as the following.
·
Ingress
of dust and moisture
·
Corrosion
·
Incorrect
installation and positioning
·
Poor
care & maintenance
·
Loose
terminal connections
·
Overloaded
branch circuits, improperly rated circuit breakers to match connected load
·
Worn-out
and obsolete circuit breakers
1.
Ingress of Dust and Moisture
Water
moisture and dust do not mix with electricity. Even when dry, dust inside a
panel board can cause electrical tracking and arcing leading to overheating and
smoldering fires, and when dust is moist or wet, the problem is even greater.
If the panel board has a light covering of dust inside, use a compressed air
canister to clean it. But if the dust coating is heavy, turn off the power and
isolate the main feeder cable [using log out & tag procedure], and use a
dry cloth and a clean paint brush to remove the dust.
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Corroded Electrical Terminals
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Never use
WD40 inside an electrical panel board, if it gets onto the circuit breakers is
can seize them solid permanently (this is explained in more detail in item 4
below). There are specialist maintenance aerosol sprays available for cleaning
electrical panel boards, but only use weak solvent types and they must have a
high-dielectric quality for energized panel boards. Aerosol sprays with a
low-dielectric means that the spray mist will conduct electricity and so if
used on an energized panel board could result in electric shock, serious injury
or worse. Good quality aerosol sprays approved for maintenance of electrical
panel boards usually have a water moisture ‘expellant’ property, which means
they will disperse moisture and water from electrical connections. Aerosol
sprays with a strong solvent will damage circuit breakers, so any aerosol
sprays for panel board maintenance must be approved by CS AAS/SCG before
use.
2.
Corrosion
Water,
moisture and condensation cause corrosion damage to circuit breakers,
electrical connections and electrical panel board steel enclosures. Corroded
circuit breakers are often stuck up and seized solid, which means they will not
operate in an electrical short circuit or emergency and in the past serious
fires have occurred as a result. Corrosion on electrical terminals can cause
bad connections, resulting on loss of service, arcing, overheating and fire.
Corrosion on panel board steel enclosures, can be so severe it causes the
entire unit to fall apart leading to a serious electrical safety hazard.
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Corroded Circuit Breaker
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All electrical equipment is rated for the type of service
application, such as indoor service, external/dry, external/wet areas, etc, by International Standard IEC 60529: Ingress Protection Rating
[IP rating] for electrical equipment, Table 2.1 below shows the rating for each
application, and indoor electrical panel boards generally have an ingress
protection rating of IP40 [no protection from water/moisture], while electrical
panel boards for occasional moist areas [such as kitchens] are IP54, and
electrical panel boards exposed to water or rain, need to be IP64/65. So water,
moisture and condensation should be kept away from electrical panel boards that
have the regular IP40 rating. Corrosion has occurred in the following areas.
A.
Indoor
electrical panel boards in an air-conditioned area, moisture can get into the
enclosure via the electrical service conduit from the outside or via conduits
connecting to non-air-conditioned ceiling voids, etc. This can be easily
corrected by applying silicone sealant the conduits entry points within the
enclosure.
B.
Electrical
panel boards are often located in mechanical rooms of houses and buildings, and
in most cases the mechanical room is an open plenum for the air-conditioning
return air. If the mechanical room door to the outside has a bad seal, warm
moist air will enter causing condensation on the outside and inside of the
electrical panel board. This can be easily corrected by repairing/replacing the
mechanical room door seals.
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Corroded Electrical Panel Board
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Ingress Protection Rating
[IP rating] for electrical equipment
Solids, first digit – the first
digit indicates the level of protection that the enclosure provides against
access to hazardous parts (e.g., electrical conductors, moving parts) and the ingress
of solid foreign objects.
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Level
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Object
size protected against
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Effective
against
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0
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—
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No protection against contact and
ingress of objects
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1
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>50 mm
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Any large surface of the body,
such as the back of a hand, but no protection against deliberate contact with
a body part
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2
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>12.5 mm
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Fingers or similar objects
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3
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>2.5 mm
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Tools, thick wires, etc.
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4
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>1 mm
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Most wires, screws, etc.
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5
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Dust protected
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Ingress of dust is not entirely
prevented, but it must not enter in sufficient quantity to interfere with the
satisfactory operation of the equipment; complete protection against contact
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6
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Dust tight
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No ingress of dust; complete
protection against contact
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Liquids, second digit – protection of the equipment inside the enclosure against
harmful ingress of water
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Level
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Protected
against
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Testing
for
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0
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Not
protected
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—
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1
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Dripping
water
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Dripping water (vertically falling
drops) shall have no harmful effect.
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2
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Dripping
water when tilted up to 15°
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Vertically dripping water shall
have no harmful effect when the enclosure is tilted at an angle up to 15°
from its normal position.
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3
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Spraying
water
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Water falling as a spray at any
angle up to 60° from the vertical shall have no harmful effect.
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4
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Splashing
water
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Water splashing against the
enclosure from any direction shall have no harmful effect.
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5
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Water
jets
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Water projected by a nozzle
(6.3mm) against enclosure from any direction shall have no harmful effects.
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6
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Powerful
water jets
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Water projected in powerful jets
(12.5mm nozzle) against the enclosure from any direction shall have no
harmful effects.
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7
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Immersion
up to 1 m
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Ingress of water in harmful
quantity shall not be possible when the enclosure is immersed in water under
defined conditions of pressure and time (up to 1 m of submersion).
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8
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Immersion
beyond 1 m
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The equipment is suitable for
continuous immersion in water under conditions which shall be specified by
the manufacturer.
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3.
Incorrect Installation and Positioning
Electrical
panel boards are often installed in the incorrect location, such as dust and
moisture enters an IP40 rated panel board in a located garage, storehouse or
similar, where building doors are frequently opened; the correct type of panel
board enclosure for this purpose is IP54 [splash and dust resistant, subjected
to occasional moisture] see Table 2.1 above.
An IP54
rated panel board is located in a frequently wetted area, such as pump room,
swimming pool area, etc, the correct type of panel board enclosure for this
purpose is IP64/65, see Table 2.1 above.
4.
Poor Care & Maintenance
A circuit
breaker is a thermo-electric device, which means it has an internal spring
device attached to a small electric heating element, and when the electrical
current in the circuit exceeds the circuit-breaker rated value, the heating
element releases the spring and quickly turns off the electrical power. The
circuit-breaker spring device is lubricated with dielectric grease, but the
circuit breaker toggle switch still needs to be operated periodically [annually
minimum] to ensure free movement.
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Poorly Maintained Circuit Breakers
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The WD40 aerosol maintenance spray has been commonly used in
electrical maintenance for several decades, and it has good water moisture expellant
properties, it is a high-dielectric so does not conduct electricity, and also a
good solvent cleaner/degreaser for electrical contacts and terminals. The
active ingredient in WD40 is naphtha [volatile hydrocarbon], which makes it
very quick drying. But naphtha is also a very strong solvent which means it
will quickly dissolve the dielectric grease inside circuit breakers, and they
will become stuck up and seized quickly afterwards. This is why WD40 must never
be used, as most circuit breakers are sealed devices and so the dielectric
grease cannot be replaced. All aerosol sprays for panel board maintenance must
be approved by CS AAS/SCG before use.
5.
Loose Terminal Connections
Loose electrical
terminal connections on circuit breakers can result in loss or service, arcing,
overheating and outbreak of fire, so it is very important to retighten the
connections periodically [annually minimum]. The terminals on the branch
circuits need to be de-energized using the main breaker before tightening, and
the terminals on the main breaker, isolate the main feeder cable [using log out
& tag procedure] before attempting to retighten the terminals.
6.
Overloaded Branch Circuits
Improperly
sized or rated circuit breakers to match connected load will often cause
frequent tripping incidents and early failure of the breaker. The rating and
sizing of circuit breakers shall be in accordance with NEC, but a good rule of
thumb is to select breakers 140% (minimum) of the full load current in
resistive circuits [lighting, convection heaters, electronic devices, cooking
appliances, etc]; and 130% (minimum) of the startup current of inductive loads
[fan motors, pumps, fan-assisted heaters, compressors, etc], this avoids
frequent nuisance tripping incidents and early failures.
7.
Worn-Out and Obsolete Circuit Breakers
As mentioned earlier in item 4 above, a thermo-electric
circuit breaker has an internal mechanical spring, which weakens and wears out
with age. Five (5) years after installation the spring will have lost some of
its tension ability, and by ten (10) years a significant portion of the tension
ability may have been lost. This means the circuit breaker may not reset
correctly after tripping, or more importantly may not operate and safely
disconnect the electrical current during overload conditions as originally
designed by the manufacturer. Accordingly, electrical panel board circuit
breakers need to be replaced with new ten (10) years after the installation
date, or when the building is renovated, whichever is the sooner. For larger
more expensive circuit breakers, a full load and function test in accordance
with the manufacturer’s instructions needs to be carried out to determine
whether the breaker disconnection time still complies with the design
specification, or replace the entire breaker, whichever is the most feasible
and cost effective.
Update:20- Jan -2016
REFERENCE
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