84
Rev. 2
SERVICING
S-14A Models with WR50A52 Ignition Control &
Radiant Sense Flame Sensor
The Radiant Sensor is a single pole double throw switch
that is activated by a combination of the heat radiating from
the burner flame, and the reflected heat from the ignitor.
Once the pressure switch contacts close, power is supplied
through the N.C. contacts of the Radiant Sensor to the gas
valves terminal 4 (GN-7 wire). When the Radiant Sensor
senses sufficient heat from the ignitor, the sensor will switch
to the N.O. position suppling 24V. to the gas valves terminal
5 (YL-8 wire).
If you should experience a flame sense problem with the
GUIB series furnace, it is important to verify correct posi-
tioning and alignment of the components before replacing
the flame sensor. The following drawing illustrates the proper
positioning and alignment of the ignitor, radiant shield, and
flame sensor.
Ignitor
(All Models)
5/16"
37°
Flame Switch
(Radient Sense Models)
Models with Integrated Ignition Control & Flame
Sensor Probe
Note: Any bending, twisting, or distortion of the electrical
tabs on the sensor will adversely affect the calibration of the
switch and result in unacceptable performance of the sen-
sor.
Refer to the Radiant Sense System Schematic in the wiring
section for details.
WARNING
Disconnect Electrical Power Supply:
1
Remove burner compartment door to gain access to the
radiant flame sensor.
2. Disconnect the wires from the Radiant Sensor.
3. Using a VOM check from common terminal to NC (Nor-
mally Closed) - should read closed. Check from Com-
mon to NO (Normally Open) - should read open.
WARNING
LINE VOLTAGE NOW PRESENT.
4. Place unit into a heating cycle.
5. Using a VOM check from chassis ground, to pin 8 FSO
(GR-9 wire) on ignition control. No power check pres-
sure switch and ignition control.
6. Within the ignitor preheat period, check from chassis
ground, to pin 12 FSI (BR-10 wire) on ignition control.
No power check BR-10 wire.
6. When the Radiant Sensor senses sufficient heat it will
close the N.O. contacts. Power should now be read at
pin 4 MV FS (VT-12 wire). No power check VT-12 wire,
replace Radiant Sensor if necessary.
7. After check and/or replacement of radiant flame sensor,
reinstall burner compartment door and verify proper unit
operation.
S-15
CHECKING MAIN BURNERS
The main burners are used to provide complete combustion
of various fuels in a limited space, and transfer this heat of
the burning process to the heat exchanger.
Proper ignition, combustion, and extinction are primarily due
to burner design, orifice sizing, gas pressure, primary and
secondary air, vent and proper seating of burners.
.023" - .027"
Beckett Burner
WARNING
Disconnect Gas and Electrical Power Supply:
In checking main burners, look for signs of rust, oversized
and undersized carry over ports restricted with foreign mate-
rial, etc as shown in the previous drawing.
