Honeywell 7800 Series Product Data page 22

7800 SERIES RM7896A,B,C,D RELAY MODULE
• Open circuits.
• Short circuits.
• Leakage paths caused by moisture, soot or
accumulated dirt.
3. For a flame rod, make sure:
• Ground area is large enough.
• Flame rod is properly located in the flame.
• Temperature at the flame rod insulator is no greater
than 500°F (260°C).
4. For all optical detectors, clean the detector viewing
window and inside of the sight pipe as applicable.
5. With the burner running, check the temperature at the
detector. If it exceeds the detector maximum rated
temperature:
• Add a heat block to stop conducted heat traveling up
the sight pipe.
• Add a shield or screen to reflect radiated heat.
• Add cooling (refer to sight pipe ventilation in the
detector Instructions).
6. Make sure that the flame adjustment is not too lean.
7. Make sure the detector is properly sighting the flame.
8. If necessary, resight or reposition the detector.
Flame
Detector
Flame Rod Photocell
C7012A,C
C7012E,F
C7015A
C7027A, C7035A,
C7044A
C7076A,D
a
This minimum or a stronger signal should easily be obtained if the detector is correctly installed and positioned to properly
sense the flame. This voltage must be obtained before completing checkout.
b
The flame amplifiers are Ampli-Check type.
c
The flame signal amplifier circuitry is tested one-half second every five seconds during burner operation and shuts down the
burner if the amplifier fails (all installations).
Initial Lightoff Check for Proved Pilot
Perform this check on all installations that use a pilot. It
should immediately follow the preliminary inspection.
NOTE: Low fuel pressure limits, if used, could be open. If
so, bypass them with jumpers during this check.
1. Open the master switch.
2. Make sure that the manual main fuel shutoff valve(s) is
closed. Open the manual pilot shutoff valve. If the pilot
takeoff is downstream from the manual main fuel shutoff
valve(s), very slightly open the manual main valve to
supply pilot gas flow. Make sure the main fuel is shutoff
just upstream from the burner inlet, or disconnect power
from the automatic main fuel valve(s).
3. Close the master switch and start the system with a call
for heat by raising the set point of the operating
controller, see Fig. 15, 16 or 18. The primary sequence
should start the ten-second INITIATE sequence.
65-0193
Table 5. Flame signal.
Acceptable Flame Minimum Maximum
Signal Amplifier Steady DC Voltage
b
R7847A,B
c
R7847C
b
R7848A,B
b
R7849A,B
R7886A
NEGATIVE (-)
METER LEAD
Fig. 20. Flame signal measurement.
a
1.25 Vdc 5.0 Vdc at the Keyboard Display Module or
5.0 Vdc at a 20K ohm/volt meter
4. Let the sequence advance through PREPURGE.
Ignition spark should occur and the pilot should light. If
the pilot ignites, the FLAME LED will be energized.
Proceed to step 7.
5. If the pilot flame is not established in four or ten seconds,
safety shutdown occurs. Let the sequence complete its
cycle. Consult the equipment operating manual for
further information.
6. Push the reset pushbutton, and let the system recycle
once. If the pilot still does not ignite, make the following
ignition/pilot adjustments:
a. Open the master switch and remove the RM7896
from the subbase.
b. On the subbase, jumper terminal 5 to ignition
terminals 8 or 10; refer to the appropriate wiring
diagram to determine the proper terminal.
Disconnect the leadwire to the pilot valve if it is
connected to the same terminal.
c. Close the master switch to energize only the ignition
transformer.
22
POSITIVE (+)
METER LEAD
20K OHM/
VOLT METER
M7554
Expected
DC Voltage