Troubleshooting - Honeywell C7915A Information

HOT REFRACTORY HOLD-IN TEST
Test to make certain that hot refractory will not cause the flame
to remain after the burner flame is extinguished. This condition
would delay response to flame failure and also would prevent a
system restart as long as the infrared radiation emitted by the
hot refractory is detected.
First check the plug-in flame signal amplifier by initiating a
burner cycle. When the system is in the
the firing cycle while the refractory is at a low temperature.
Measure the time it takes for the flame signal LED to go out
after the flame goes out. If the flame signal LED fails to go out
within four seconds, open the master switch and replace the
amplifier.
Infrared detectors can respond to infrared radiation emitted by
a hot refractory, even when the refractory has visibly ceased to
glow. Infrared radiation from a hot refractory is steady, whereas
radiation from a flame has a flickering characteristic. The
infrared detection system responds only to a flickering infrared
radiation; it can reject a steady signal from hot refractory.
However, the refractory's steady signal can be made to
fluctuate if it is reflected, bent, or blocked by smoke or fuel mist
within the combustion chamber. Be careful when applying an
infrared system to ensure its response to flame only.
To check a C7915A Infrared Flame Detector
hold-in, operate the burner until the refractory reaches its
maximum temperature. If the installation has a multifuel burner,
burn the fuel most likely to reflect, bend, or obscure the hot
refractory's steady infrared radiation (burn solids instead of
liquids, or liquids instead of gases). When the maximum
refractory temperature is reached, close all manual fuel shutoff
valves or open the electrical circuits of all automatic fuel valves.
Visually observe when the burner flame goes out. After the
flame goes out, measure the time it takes for the flame signal
LED to go out. If the flame signal LED fails to go out within four
seconds, the infrared detector is sensing the radiation from hot
refractory. Immediately terminate the firing cycle (lower the set
point of the burner controller, or set the fuel selector switch to
OFF). Do not open the master switch.
NOTE: Some burners continue to purge their oil lines
between the valves and nozzles even though the fuel
valve(s) is closed. Terminating the firing cycle
(instead of opening the master switch) will allow purg-
ing of the combustion chamber. This will reduce a
buildup of fuel vapors in the combustion chamber
caused by oil line purging.
If the detector is sensing hot refractory radiation
must be corrected. Add an orifice plate in front of the photocell
to restrict the detector viewing area. If this does not work,
resight the detector at a cooler, more distant part of the
combustion chamber. While resighting the detector, remember
that it must also properly sight the flame. Lengthening the sight
pipe or decreasing the pipe size (diameter) may also be
helpful. For details, refer to Installation. Continue adjustments
until hot refractory hold-in is eliminated.
IGNITION INTERFERENCE TEST
It is possible for infrared amplifiers to respond to ignition spark
electrical noise (interference) under certain conditions. Avoid
ignition interference by locating the transformer as close as
possible to the burner ignition electrode (preferably not on the
control cabinet). You can also use an ignition cable that
run
position, terminate
for hot refractory
, the condition
11
C7915A INFRARED FLAME DETECTOR
suppresses electrical noise (such as the type of cable used in
automobiles). Maintain maximum separation of flame sensor
and ignition wiring.
To determine if an infrared flame amplifier responds to ignition
interference, complete the following test sequence:
1. CLOSE MANUAL FUEL VALVES TO THE PILOT AND
MAIN BURNER.
2. Connect a flame signal meter to the amplifier and start
the burner.
3. There should be no flame signal when the ignitor is ener-
gized (momentary meter movement may be observed
when the flame safeguard control switches a load on or
off).
WELD THE SIGHT PIPE
After adjustments have been made and an acceptable flame
signal obtained, remove the detector and weld the sight pipe in
its final position (if you are using a swivel mount, the pipe may
already be welded). Then reinstall the detector.
FINAL CHECKOUT
Before putting the burner into service, check out the installation
by 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 proper operation.
CAUTION
Complete Checkout Tests.
Do not put the system into operation until all Checkout
tests in the instructions for the appropriate flame
safeguard control and any specified in the burner
installation instructions are satisfactorily completed.

TROUBLESHOOTING

CAUTION
Electrical Shock Hazard. Be extremely careful while
troubleshooting the detector; line voltage is present on
some of the terminals on the wiring subbase or
terminal strip when power is on. Open the master
switch to disconnect power before removing or
installing the detector, there may be more than one
disconnect involved.
If you cannot obtain a satisfactory flame signal while adjusting
the sighting position of the detector, follow these procedures. If
you encounter other problems in the system, refer to
Troubleshooting in the instructions for the appropriate flame
safeguard control.
EQUIPMENT REQUIRED
1. Voltmeter (Honeywell W136A or equivalent) with 0 to 300
Vac scale.
2. A one megohm/volt meter with a zero to 5 or 10 Vdc
scale is recommended for 7800 SERIES, R7140 control
flame voltage measurements. If the control has the Key-
board Display Module option, flame voltage is displayed
on the module.
3. Replacement parts—see Specifications.
65-0292-06