Quantcast Bus bar and terminal connections

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TM 5-683/NAWAC MO-116/AFJMAN 32-1083
tight indefinitely. If signs of arcing are evident, then
contact lubricant to the stationary studs and to the
the connections should be broken and the connect-
primary disconnects on the breaker.
ing surfaces cleaned. Because of the different char-
l. Ensure that all metal shields are securely in
acteristics of copper and aluminum, they should not
place. These shields must be installed to confine any
be intermixed in a terminal or splicing connector
blast in the event of circuit breaker failure.
where physical contact occurs between them, unless
(1) A note on lubricants. One of the most useful
the device is suitable for the purpose and conditions
lubricants for motors is an extreme pressure (EP)
of use. Materials such as solder and compounds
lithium-base petroleum grease. As the usage of
shall be suitable for the use and shall be of a type
Class F winding temperature ratings has increased,
which will not adversely affect the conductors.
however, others have adopted synthetic greases to
a. Aluminum connectors. Special considerations
withstand higher bearing temperatures.
must be given to aluminum connections. Aluminum
(2) Synthetic oils and greases. Synthetic oils
connectors are plated and should not be cleaned
and greases compounded from various silicones,
with abrasive. If these connectors are damaged,
alkyl benzene, diesters, and fluorinated ethers, are
they should be replaced. It should be noted that
available for extremely high-temperature service
when making connections with aluminum conduc-
that would cause premature oxidation of petroleum
tors, be sure to use a joint compound made for the
lubricants. Some synthetics also suit extremely low
purpose. To assist in the proper and safe use of solid
temperature, down to 40 or 50 degrees below zero.
aluminum wire in making connections to wiring
The main uses for synthetic lubricants in motor
devices, refer to the National Electrical Code. Make
bearings are reduced friction and resistance to
aluminum connections with solderless circumferen-
moisture and chemical contamination. Such appli-
tial compression-type, aluminum-bodied connectors
cations must be carefully worked out with bearing
UL listed for AL/CU. Remove surface oxides from
and lubricant suppliers, because no universal lubri-
aluminum conductors by wire brushing and imme-
cant formulation will apply to all environments.
diately apply oxide-inhibiting joint compound and
However, it is not unusual for lubricant to vary
insert in connector. After joint is made, wipe away
little more than brand name. Thus substitutions are
excess joint compound and insulate splice.
often possible. Consult with the manufacturer of the
b. Bus insulators and barriers. Bus bar support
switchgear to determine the important characteris-
insulators and/or barriers should be wiped with a
tics of the lubricant prior to specifying a substitute
clean cloth. Do not use steel wool or oxide papers to
lubricant. Carefully selected substitutes will reduce
remove dirt; use a cleaning solvent that will not
the cost of procurement, stocking and dispensing.
leave trace deposits. While cleaning, check insula-
2-3. Bus bar and terminal connections.
tors for cracks and signs of arc tracking. Defective
Many failures are attributable to improper termina-
units should be replaced. Loose mounting hardware
tions, poor workmanship, and different characteris-
should be tightened.
tics of dissimilar metals. Loose bus bar or terminal
2-4. Underfloor ducts.
connections will cause overheating which can be
easily spotted by a discoloration of the bus bar. A
All undefloor duct systems require checks for evi-
dence of oil and water. Entrances and fittings
thermographic survey can be conducted to detect
overheating before discoloration occurs (para 14-7).
should be checked and corrected as necessary to
An overheating condition will lead to deterioration
prevent entrance of liquids, insects, and rodents.
of the bus system as well as to equipment connected
Cockroaches, ants, beetles and rodents have been
to the bus; i.e. protective devices, bus stabs, etc.
known to attack cable insulation, especially if
Therefore, bus bar and terminal connections should
greases or oils are present. External heat and heat
be regularly checked to ensure that they are prop-
caused by overloaded circuits can cause cracking of
erly tightened without damaging the conductors.
cable insulation and drying of taped splices. Mois-
Special attention should be given where excessive
ture can then penetrate the cable and could cause a
vibration may cause loosening of bolted bus and
fault. Therefore, underfloor conduits and duct sys-
terminal connections. Tightening torque values for
tems should be kept sufficiently clear of electrical
electrical connections are provided in table 21.
and hot water floor-heating systems to prevent un-
This information should be used for guidance only
due heating of the enclosures.
where no tightening information on the specific con-
2-5. Busways.
nector is available. It should not be used to replace
manufacturer's instructions which should always be
Feeder busway, trolley busway and plug-in busway
followed. Do not assume that once a connection has
(fig 21) require annual cleaning and removal of oil
been torqued to its proper value that it remains
substances and dirt. Ventilated-type busway should
2-2





 


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