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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
circuit to ground (fig 8-6). It will not eliminate the
(b) Make sure that the power tool is
grounded through the additional grounding conduc-
shock sensation since the normal perception level is
tor in the cord and the grounding prong of the plug.
approximately 0.5 mA. It will not protect from elec-
The integrity of this ground circuit is necessary for
trocution upon line-to-line contact since the nature
the Protection of personnel.
of line-to-line loads cannot be distinguished by a
line-to-ground device. GFIs are sealed at the fac-
(c) Make sure that the cord is not cut, bro-
ken, spliced or frayed. Cords maybe replaced or the
tory, and maintenance should be limited to that
recommended by the manufacturer. Tripping tests
damaged portion may be cut out and the two sec-
tions rejoined by attaching a plug and connector.
should be performed with the test button on the
unit in accordance with the frequency recommended
(d) Make sure that the green conductor is
connected to the frame of the tool and the grounding
by the manufacturer. Results and dates of tests
should be recorded on the test record label or card
prong of the attachment plug.
supplied with each permanently installed GFI unit.
(4) Permanent type. A permanently mounted
type GFI is a self-contained, enclosed unit designed
There are four types of GFIs. There are circuit
to be wall or pole mounted and permanently wired
breaker type, receptacle type, portable type, and
into the circuit to be protected. Maintenance beyond
permanently mounted type.
tightening of connections and cleaning should not
(1) Circuit breaker type. A circuit breaker type
GFI is designed in the form of a small circuit
be attempted. Any repairs needed should be re-
ferred to the manufacturer.
breaker and is completely self-contained within the
unit housing. The circuit breaker type GFI provides
b. Ground fault protectors (GFP). A GFP is de-
overload and short-circuit protection for the circuit
signed to limit damage to electrical equipment in
conductors in addition to ground-fault protection for
the event of a fault (either solid or arcing) between a
live part of the protected circuit and ground. A GFP
personnel. It is intended to be mounted in a
panelboard or other enclosure. For required mainte-
will cause the circuit to be disconnected when a
nance refer to paragraph 5-4c.
current equal to or higher than its setting flows to
ground (fig 8-7). GFPs are available with settings
(2) Receptable type. A receptacle type GFI is de-
signed in the form of a standard receptacle that is
typically ranging from five to 1200 amperes. It will
completely self-contained within the unit housing,
not protect personnel from electrocution. A GFP sys-
and does not provide overload or short-circuit protec-
tem is designed to be installed in a grounded distri-
tion. It is intended for permanent installation in con-
b u t i o n system. I t c o n s i s t s o f t h r e e m a i n
ventional device outlet boxes or other suitable enclo-
components: sensors; relay or control unit; and a
sures. Maintenance required for a GFI receptacle is
tripping means for the disconnect device controlling
the same as any standard receptacle outlet. If the
the protected circuit. Detection of ground-fault cur-
GFI receptacle does not reset, is badly worn, cracked,
rent is done by either of two basic methods. With
or broken, or if contacts are exposed, the GFI must be
one method, ground current is detected by sensing
replaced. It should also be replaced if accidental dis-
current flow in the grounding conductor. With the
engagement of a plug from the receptacle is a recur-
other method, all conductor currents are monitored
ring problem. Proper wire connections on the recep-
by either a single large sensor, or several smaller
tacle and proper polarity of power connections should
ones. Sensors are generally a type of current trans-
be checked including the integrity of the equipment
former and are installed on the circuit conductors.
ground. If there is abnormal heating on the GFI
The relay or control unit maybe mounted remotely
receptacle face, check for loose terminal connections
from the sensors or maybe integral with the sensor
and correct or replace. If there is evidence of burning
assembly. Circuit breakers with electronic trip units
or arc-tracking, it should be replaced.
may have a GFP system integral with the circuit
(3) Portable type. A portable type GFI is a unit
breaker. Any maintenance work performed on the
intended to be easily transported and plugged into
electronic circuitry should adhere to manufacturer's
any grounded receptacle outlet. Cords, tools or other
instructions. Maintenance on the mechanical oper-
devices to be provided with ground-fault protection
ating mechanism components should be performed
for personnel are then plugged into receptacles
as recommended in chapter 5. Maintenance require-
mounted in the unit. Required maintenance would
ments for the sensors are as specified in chapter 2
include that recommended in paragraph (2) above
for instrument transformers. Tighten all terminal
for receptacle type GFIs along with the following
connections and clean. Any repairs needed should
cord care recommendations:
be performed by the manufacturer. If interconnec-
tions between components are disconnected, they
(a) Keep the cord free of oil, grease and other
material that may ruin the rubber cover. Avoid tan-
must be marked and replaced to maintain the
gling knots or dragging across sharp surfaces.
8-12
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