1. Remove the belt and loosen the set screw in the adjustable
flange of the motor pulley.
2. Close the pulley to decrease the temperature rise; open
the pulley to increase the rise.
3. Position the set screw with one of the flats on the pulley
hub and tighten it.
4. Align the fixed flange of the motor pulley with the blower
pulley.
CAUTION: improper alignment will cause excessive
noise, belt wear, and bearing failure.
5. Replace the belt and adjust the tension until the belt can
be depressed 1" with a finger at a point halfway between
the two pulleys.
6. Repeat this procedure untilt he desired temperature rise is
obtained.
ADJUSTMENT OF FAN CONTROL SETTINGS
Place a thermometer in the heated air duct, about six feet from
the furnace, where it won’t be affected by radiant heat. Usually
the fan control is set so that the thermometer reads about 125
°
F
when the blower starts, and about 85
°
F when it stops.
The Fan On setting of the fan control must be high enough to
allow the air in the furnace to be heated enough so that no cold
air is blown into the heated space, but not so high that the
furnace might be damaged by excessive heat.
To adjust the Fan On setting:
1. Turn the furnace on.
2. Read the thermometer when the blower starts.
3. If this temperature is too high when the blower starts, lower
the fan on setting. If the temperature is too low, raise the
setting.
4. If adjustments are made to the fan on setting, check the
operation of the furnace by repeating the previous steps.
The Fan Off setting must be low enough to adequately cool
the furnace, but not so low that cold air is blown into the
heated space.
To adjust the Fan Off setting:
1. Turn the furnace on.
2. Let the furnace operate for 20 minutes.
3. Turn 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.
CAUTION: When fan on and fan off adjustments are
made, be careful not to rotate the fan control dial. If
the dial is allowed to rotate, the control could be
damaged and operate erratically.
CHECKING LIMIT CONTROL
With the main burners operating, cover all return air grilles with
paper to restrict the flow of return air. In a few minutes the
burners should be shut off by the limit control. Remove the
return air restrictions. The main blower will cool the unit. The
limit switch should reclose and the main burners relight after
the proper re-start period.
OPERATION AND MAINTENANCE
SEQUENCE OF OPERATION
Hot Surface Ignition System
WARNING: Do not attempt to relight 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 diagrams (pages 14 & 15)
for component locations.
CONTINUOUS BLOWER
On cooling/heating units with fan switch, when the fan switch
is set in the ON position, a circuit is completed between
terminals R and G of the thermostat. This energizes the 1R
relay. Contact 1R-1 closes and contact 1R-2 opens. The motor
is energized through the black, high speed tap. The blower then
operates on high speed.
INTERMITTENT BLOWER
When the system 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 (1LP) activates the 50E47 ignition control.
The rollout switch control, primary limit and auxiliary limit are
also in this circuit and must be in the closed position for the
ignition control to be 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 terminals R and W is opened.
After approximately 60 seconds (or the supply air temperature
reaches 155
°
to 125
°
F), the fan switch closes. When the
thermostat opens, the venter is de-energized, along with the
ignition control. With the ignition control de-energized, the gas
flow stops and the burner flames are extinguished.
The blower motor continues to operate until the supply air
temperature drops to between 85
°
and 100
°
F. When this oc-
curs, the fan switch opens, de-energizing the blower motor. The
heating cycle is then complete, and the unit is ready for the start
of the next heating cycle.
If flame is not detected in 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 SERIES HOT SURFACE IGNITION CONTROL
All White-Rodgers 50E47 controls will repeat the ignition se-
quence for a total of five recycles is flame is lost within the first
10 seconds of establishment.
650.64-N4
10
Unitary Products Group
