Service; Troubleshooting - Honeywell 7800 Series Manual

Ultraviolet Response Tests Ignition Spark
Response Test
Test to be sure that ignition spark is not actuating the flame
relay in the flame safeguard control.
1. Close the pilot and main burner manual shutoff valves.
2. Start the CR7890 and run through the Ignition period.
Ignition spark should occur, but the flame LED must not
light. The flame signal should not be greater than 0.25
Vdc.
3. If the flame relay does pull in, reposition the CR7890
farther from the spark, relocate or resight the CR7890 to
eliminate or reduce the CR7890 response to reflected
UV radiation. It may be necessary to construct a barrier
to block the ignition spark from the CR7890 view.
Continue adjustments until the flame signal due to
ignition spark is less than the flame signal values
indicated in step 2.
Weld the Sight Pipe
When the flame signal is acceptable after all adjustments are
made, remove the CR7890 and weld the sight pipe in its final
position. (If you are using a swivel mount, the pipe may be
already welded.) Then reinstall the CR7890.
Final Checkout
Before putting the burner into service, check out the
installation using the Checkout procedures in the Instructions
for the appropriate flame safeguard control. After completing
the Checkout, run the burner through at least one complete
cycle to verify correct operation.
IMPORTANT
Do not put the system into operation until all
Checkout tests in the Instructions for the appropriate
flame safeguard control and any others specified in
the burner installation instructions are satisfactorily
completed.

SERVICE

WARNING
Electrical Shock Hazard.
Can cause serious injury or death.
Open the master switch to disconnect power before
removing or installing the CR7890 or its cover. More
than one disconnect can be involved.
Periodic Maintenance
1. Clean the viewing window (or focusing lens) when
necessary. Remove the CR7890 (see Troubleshooting
section) and use a clean cloth over the eraser end of a
pencil. Do not remove the window (or lens) to clean it. If
it is broken or damaged or it is coated with a substance
that cannot be removed, replace the CR7890 (see Fig.
13).
2. Keep the CR7890 adjusted for the smoothest, most
reliable operation as recommended by the burner
manufacturer.
CR7890B 7800 SERIES INTEGRATED BURNER CONTROL

TROUBLESHOOTING

WARNING
Electrical Shock Hazard.
Can cause serious injury or death.
Open the master switch to disconnect power before
removing or installing the CR7890 or its cover. More
than one disconnect can be involved.
Equipment Required
For 7800 SERIES controls, a voltohmmeter with an input
impedance of one megohm/volt and a zero-to-five or
zero-to-ten Vdc scale is suggested.
Unsatisfactory Flame Signal
If a satisfactory flame signal cannot be obtained while
adjusting the sighting position of the CR7890, consider
124204 Quartz Focusing Lens. If you encounter other
problems in the system, refer to the Troubleshooting section in
the instructions for the appropriate flame safeguard control.
Troubleshooting Procedures
First perform the Preliminary Inspection. Then follow the
applicable procedures for either a low meter reading or a zero
meter reading. After reinstalling the CR7890 or replacing its
cover, recheck the meter reading. To try to obtain the proper
flame signal, adjust the position of the CR7890. If you
complete all of the procedures and yet cannot obtain a proper
flame signal, replace the CR7890.
Preliminary Inspection
1. Check for the proper line voltage. Make sure the master
switch is closed, connections are correct, and power
supply is of the correct voltage and frequency.
2. Check the CR7890 wiring for defects:
a. Incorrect connections.
b. Wrong type or size of wire.
c. Deteriorated wire.
d. Open circuits.
e. Short circuits.
f. Leakage paths caused by moisture, soot, or dirt.
3. With the burner running, check the temperature at the
CR7890. If it exceeds 135°F (57°C) [see Table 4]:
a. Add additional insulation between the wall of the
combustion chamber and the CR7890.
b. Add a shield or screen to reflect radiated heat away
from the CR7890, or
c. Add cooling (refer to Sight Pipe Ventilation and
Accessories sections).
Removing CR7890 from Sight Pipe (Refer to
Fig. 7)
Loosen the three screws holding the mounting flange; rotate
the CR7890 slightly so the screws clear the slots in the back
section of the flange; separate the flange; and pull off the back
section (with the UV sensor).
NOTE: The CR7890 is free when the collar is unscrewed; do
not drop it.
13 65-0259—1