Coleman 7600 - Limit Switches

INSTALLATION
INSTRUCTIONS
FAN
SWITCHES
'I'he
furnace is equipped
with one
fan
switch
located
at the
top of the control
panel. This
switch
is
a
nor-
mally
open
switch
that closes
with a
rise
in tempera-
ture.
The
fan switch
is
a
disc
type switch
that
is
calibrated
to close at
105', and open
at 90o.
As in the case ol a
limit switch,
the
temperature
on
the
fan switch does
not
necessarily
mean that
the air
will
be
the same
temperature.
A fan switch,
due
to
its loca-
tion
on the
furnace, might actually
start
the blower at
an
outlet air
temperature
that
is
above
the calibrated
temperature.
The disc switches
used are
marked
to indicate
the tem-
perature
at which
the switch
will open
or close
and
the type switch
being used.
For example,
a marking
of
Fl40-30
means that
the switch
is
a
fan switch set
to turn
the blower
on at
l40o
and
shut
of at
ll0o
(140-30=
I l0).
ELECTRICAL
TERMINALS
THRUST
EUTTON
BI.METAL OISC.: HOT
CIRCUIT
CLOSED
FAN SWITCH
LIMIT
SWITCHES
Each furnace
is equipped
with two
limit
switches.
The
upper
limit switch
is
located on
the
left
side of the
blower
housing
in the blower
compartment.
The
upper
limit
shuts the
furnace
off
in case
the upper
portion
of
the
furnace
overheats.
An overheating
condition
could
exist
at the
top
of the
furnace
because
of circulating
blower
failure. electrical
failure, or
overfiring
of the
furnace.
The
lower
limit shuts
the
lurnace olf
in case
of exces-
sive
heat build
up
in the
lower
portion
ol
the
furnace'
The
lower limit
switch
is located
at
the bottom
of
the
control
wiring box.
Some
common
causes
of
overheating
in
this
region
are
restricted ducts,
too
many
floor
registers
closed,
or
restricted
inlet,
i.e. dirty
filter,
clothes
hanging
near or over
the inlet area.
The
lower
limit will automatically
reset
when the air
temperature
has cooled
down.
The disk thermoswitch
is
operated
by
the
heating and
cooling
of a
bi-metal
disk.
Under
"hot"
conditions,
the bi-metal
disk
will snap
inward thrusting
the elec-
trical
contacts
open;
thereby
breaking
the
electrical
circuit.
Upon cooling,
the bi-metal
disk
will snap
back
out and
let the
contacts
close
which
will
then
let
elec-
trical
power pass
through
without
interruption.
ELECTRICAL
MOVEAELE
CONTACT
BI.METAL
DISC.. HOT
CIRCUIT
OPEN
Br-METAL OrSC.
-
COOL
crRcutT
cLosEo
LIMIT
SWITCH
MOVEABLE
CONTACT
MOVEABLE
CONTACT
BI.METAL
DISC.--
COOL
CIRCUIT OPEN
l5