4
Description
This furnace can be installed in the
upflow, downflow, or horizontal po-
sition. Figure 1 shows a typical
model in the downflow position and
figure 2 shows a typical model in
the upflow position. The furnace
may also lie on either side in a
horizontal position. The furnace is
equipped with an induced-draft vent
blower and atmospheric burners.
Combustion air is taken from the
space or area in which the furnace
is installed and drawn into the
burners through the louvers in the
front panel. Flue gas is drawn from
the furnace by the vent blower and
discharged through the flue pipe to
the outside atmosphere.
This is a forced air furnace. The
furnace circulating air blower draws
cool air from the house, passes it
over the hot furnace heat ex-
changer and circulates the warmed
air through the ductwork to the
house.
The furnace is equipped with the
controls necessary for proper op-
eration. The various components
referred to in this manual and on
the furnace nameplate are identi-
fied in Figures 1 and 2.
Sequence of Operation
These furnaces are equipped with
an electric hot surface burner igni-
tion system. In response to a call
for heat by the room thermostat,
the burners are lighted by a hot
glowing ignitor at the beginning of
each operation cycle. The burners
will continue to operate until the
thermostat is satisfied at which time
all burner flame is extinguished.
During the off cycle no gas is con-
sumed. With the room thermostat
set below room temperature, and
with the electrical power and gas
supply to the furnace on, the nor-
mal sequence of operation is as
follows:
1. When the room temperature
falls below the setting of the
room thermostat, the thermo-
stat energizes the furnace con-
trol board.
2. When the furnace control
board is activated, the vent
blower is turned on. A circuit
is also made through the
normally open pressure
switch contacts.
3. As the vent blower in-
creases in speed, the con-
tacts of the pressure switch
will close and complete the
electrical circuit to the igni-
tor.
4. During the next 15-30 sec-
onds, the vent blower will
bring fresh air into the heat
exchanger and the ignitor
will begin to glow. At the
end of this period, the gas
valve will open and the
burners will light.
5. After the burners light, a
separate sensor acts as a
flame probe to check for the
presence of flame. As long
as flame is present, the
system will monitor it and
hold the gas valve open.
6. If the burners fail to light
within 6-8 seconds after the
gas valve opens, the gas
valve will close and the ig-
nitor will be turned off. After
a short pause, the system
will recycle and try again for
ignition. If the burners fail to
light after three tries, the ig-
nition system will lock out.
The system will remain in
lockout mode until one hour
has passed, or until the
room thermostat is cycled
off then back on. The fur-
nace will then try for ignition
again.
7. The lapsed time from the
moment the room thermo-
stat closes to when the
burner light may be 30-40
seconds. This delay is
caused by (1) the time re-
quired for the vent blower to
come to full speed, (2) the
time required for the ignitor
to heat up and (3) the time
required for fresh air to be
brought into the heat ex-
changer.
8. Thirty to forty seconds after
the burners have lighted,
the fan switch will close and
the furnace air circulation
blower will run.
9. When room thermostat is
satisfied, the circuit to the
furnace control board is
broken. The circuit to the
gas valve is broken and the
burners are extinguished.
The vent blower will con-
tinue to run for a few sec-
onds. The furnace control
board will keep the circulat-
ing blower running for a
fixed period of time to allow
additional heat to be drawn
from the heat exchanger.
Furnace Operation
Safety Information
For your safety read before op-
erating:
If you do not follow these
instructions exactly, a fire
or explosion may result
causing property damage,
personal injury or loss of
life.
1. This appliance does not
have a pilot. It is equipped
with an ignition device
which automatically lights
the burners. DO NOT try to
light the burners by hand.
2. Before operating, smell all
around the appliance area
for gas. Be sure to smell
next to the floor because
some gas is heavier than air
and will settle on the floor.
What to do if you smell gas
:
•
Do not try to light any
appliance.
•
Do not touch any electrical
switch; do not use any
phone in your building
•
Immediately
call
your
gas
supplier from a neighbor’s
phone. Follow the gas
supplier’s instructions.
•
If you cannot reach your
gas supplier, call the fire
department.
