"How
does a ground
fault circuit
interrupter
(GFCI)
function?"
A
GFCI has a
transformer in
its circuitry
that senses the
balance of
current in the
circuit.
Current moves
through a
circuit at
exactly the
same rate for
the power
source to the
intended
ground, called
a neutral. As
long as this
balance exists,
the contacts in
the GFCI remain
closed.
If
any current (.5
milliamps) gets
diverted to a
foreign ground,
the GFCI opens
the circuit. A
foreign ground
is anything
other than the
intended ground
(e.g., an
electric
appliance
dropped into a
tub of water.)
Electricity
travels at the
speed of light
(186,000 miles
per second);
therefore, a
GFCI will react
to an imbalance
in about
one 40,000th of
a second.
Dates
regarding
G.FCI's!
1971:
Outdoors, and
within 15' of
swimming pool
1975:
Bathrooms
1978:
Garages and
fountains
1981:
Whirlpools and
tubs, etc.
1984:
Motel
bathrooms,
replacement for
non-grounding
receptacles
1987:
Kitchens within
6' of sink, (1)
in a basement,
boathouses
1990:
All in
unfinished
basements,
crawl spaces
1993:
Wet bar sinks
1996:
All kitchen
counter-top
receptacles;
dedicated
circuits in
bathrooms; all
outdoor
receptacles, in
sheds,
balconies,
weather
accessible from
grade level or
not; electric
car chargers
"What
is a circuit
breaker?"
A
circuit breaker
reacts to the
amount of
current that
moves through a
circuit. When
the rated
amperage of a
circuit breaker
is exceeded,
the circuit
breaker will
open.
'What does the ground wire
in a three
pronged outlet do?"
The
ground (bare)
wire is a
backup to the
neutral (white)
wire.
"What
are the pros
and cons of
circuit
breakers vs.
fuses?"
The
main advantage
of circuit
breakers is
convenience.
They are
typically sized
properly and
homeowners are
not likely to
replace them.
The
disadvantages
are that they
have moving
parts, the
connections are
somewhat less
dependable,
and, in a humid
or moist
location, the
metal contacts
have a tendency
to oxidize
after a number
of years. Also,
circuits with
motors may not
operate as
proficiently as
they should.
The
advantages of
fuses are that
there are no
moving parts
and they will
open the first
time the rated
amperage is
exceeded,
whether the
fuse is new or
80 years old.
The
disadvantages
are
inconvenience
and the
possibility of
choosing
incorrect
sizes, thus
compromising
the overload
protection or
safety.
"How
does
electricity
flow through a
circuit?"
Alternating
current (AC)
actually flows
both ways in a
circuit. The
train analogy
may help to
explain the
concept. The
engine of the
train is the
ground and the
cars represent
the current.
Current does
not move unless
a ground is
present. If the
engine is going
40 miles per
hour, the cars
will also
travel at 40
miles per hour,
If the engine
speeds up or
slows down, the
cars will
follow. The
speed of the
train is the
same as the
load on a
circuit
(i.e.,
the
accumulation of
lights,
equipment,
and/or
appliances on
the circuit.)
"What
is reversed
polarity and
what effect
does it have in
an electrical
circuit?"
Reversed
polarity is
when the hot
wire (black) is
installed on
the neutral (or
ground) side of
an outlet or
circuit and the
neutral (white)
on the hot
side. In a
circuit with
only resistance
appliances
(such as
incandescent
light bulbs),
there are no
operating
problems
because the
alternating
current flows
both ways in
these
appliances.
(Note: These
are safety
concerns for
a service
contractor.)
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