they will not be affected by radiant heat. Increase the blower
speed to decrease the temperature rise; decrease the blower
speed to increase the rise.
All direct-drive b!owers have multi-speed blowers. Refer to the
unit wiring diagram and connect the blower motor for .the
desired speed. The blower motor speed taps are located in the
control
box
in the blower compartment.
ADJUSTMEN T OF FAN CONTROL SETTINGS
NOTE:
Fan-On time is preset and not adjustable. When the
main gas valve is energized (ON), two wires carry 24v to
a smaff heater which controls fan-on timing.
To adjust the Fan Off setting:
1. Tum the furnace on.
2. Let the furnace operate for 20 minutes.
3. Tum the furnace off.
4. Read the thermometer when the blower stops.
5. If this temperature is too high when the blower stops, lower
the fan off setting; if the temperature is too low, raise the
setting.
6. If adjustments are made to the fan off setting, check the
operation of the furnace by repeating the previous steps.
CAUTIO&: Vv'hen fan on and fan off adjustments are made,
be
careful not to rotate the fan control dial. If the dial is a !lowed
to rotate, the control could
be
damaged and operate
erratically.
CHECKING
LIMIT CONTROL
With the main burners operating, cover all retum air grilles with
paper to restrict the flow of retutn air. In a few minutes, the
burners should be shut off by the limit control. Remove the
retum air restrictions. The main blower will cool the unit. The
limit switch should reclose and main burners relight after the
proper re-start period.
OPERATION
&
MAINTENANCE
SEQUE
NC
E OF OPERATION
Hot Surface Ignition System
WARNING: Do not attempt to light this furnace by hand (with
a match or any other means). There may be a potential
shock hazard from the components of the hot surface
ignition system. The furnace can only be lit automatically
by its hot surface ignition system.
The following describes the sequence of operation of the
furnace. Refer to the schematic wiring diagram (pages 16 and
17) for component location.
Conti nuous
Blower
On the cooling/heating units with fan switch, )Vhen the fan
switch is set in the ON position, a circuit is completed between
terminals R and·
G
of the thermostat. This energizes the 1
R
relay. Contact 1 R-1 closes and contact 1 R-2 opens. The motor
is energized through the black, high-speed tap. The blower
then operates on high speed.
650.65-N2
Intermittent Blower
When the system switch is set on HEAT and the fan switch
is
set on AUTO, and the room thermostat calls for heat, a circuit
is completed between terminals R and W of the thermostat.
This energizes the venter relay 3R, which energizes the venter.
When the proper amount of combustion air is being provided,
a pressure switch activates the SOE47 ignition control. A sec
ond and third pressure switch (2LP or 3LP and 4LP)(not used
in all models), the fusible link (FL) and the limit are in this circuit,
and must be in the closed position for the ignition control to b e
activated.
The 50E47 ignition control provides a 45-second warm-up
period. The gas valve then opens for four seconds.
·As gas starts to flow and ignition occurs, the flame sensor
begins its sensing function. If a flame is detected within four
seconds after ignition, normal furnace operation continues until
the thermostat circuit between R and W is opened. When the
supply air temperature reaches 115 to 125°F, the fan switch
closes.
When the thermostat circuit opens, the venter is deenergized,
along with the ignition control. With the ignition control deener
gized, the gas flow stops and the burner flames are extin
guished.
The blower motor continues to operate until the supply air
temperature drops to between 85 and 100°F. When this occurs.
the fan switch opens, de-energizing the blower motor. The
heating cycle is then complete, and the unit is ready for the stan
of the next heating cycle.
If flame is not detected within the four second sensing period.
the gas valve is de-energized. The 50E47 control is equipped
with a re-try option. This provides a 60-second wait following
an unsuccessful ignition attempt (flame not detected). After the
60 second wait, the ignition sequence is restarted with an
additional 10 seconds of igniter warm-up time. If this ignition
attempt is unsuccessful, one more re-try will
be
made before
lockout.
50E47
HOT SURFACE tGNITION CONTROL
All 50E47 controls will repeat the ignition sequence for a total
of five recycles if flame is lost within the first 10 seconds of
establishment.
If flame is established for more than 10 seconds after ignition,
the· controller will clear the ignition attempt (re-try) counter. If
flame is lost after 10 seconds, it will restart the ignition se
quence. This can occur a maximum of five times.
During burner operation, a r:nomentary loss of power of 50
milliseconds or longer will drop out the main gas valve. When
the power is restored, the gas valve will remain de-energized,
and a restart of the ignition sequence will begin immediately.
A momentary loss of gas supply, flame blowout, or a shorted
or open condition in the flame probe circuit will
be
sensed within
0.8 seconds. The gas valve will de-energize and the control will
restart the ignition sequence after waiting 60 seconds.·
Recy-
cles will begin and the bumer wHI operate normally if the gas
supply returns, or the fault condition is corrected prior to the
last ignition attempt. Otherwise, the control will lockout.
13
