Honeywell 7800 Series Manual page 17

As an option, the flame signal can be checked by using the
optional Keyboard Display Module.
If the signal is unstable or less than the minimum
acceptable voltage, check the flame detector installation
and circuitry:
1. Check the supply voltages at terminals 3 (L1) and L2
(N). Make sure the master switch is closed, connections are
correct, and the power supply is of the correct voltage and
frequency.
2. Check the detector wiring for defects including:
• Incorrect connections.
• Wrong type of wire.
• Deteriorated wire.
• Open circuits.
• Short circuits.
• Leakage paths caused by moisture, soot or accu-
mulated 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 that the detector is properly sighting the
flame.
8. If necessary, resight or reposition the detector.
IGNITION INTERFERENCE TEST
(All Flame Rods)
Test to be sure that a false signal from a spark ignition
system is not superimposed on the flame signal.
Ignition interference can subtract from (decrease) or
add to (increase) the flame signal. If it decreases the
flame signal enough, it will cause a safety shutdown. If it
increases the flame signal, it could cause the FLAME LED to
come on when the true flame signal is below the minimum
acceptable value.
Start the burner and measure the flame signal with both
ignition and pilot (or main burner) on, and then with only the
pilot (or main burner) on. Any significant difference
(greater than .5 Vdc) indicates ignition interference.
TO ELIMINATE IGNITION INTERFERENCE
1. Make sure there is enough ground area.
2. Be sure the ignition electrode and the flame rod are on
opposite sides of the ground area.
3. Check for correct spacing on the ignition electrode:
a. 6,000V systems—1/16 to 3/32 in. [1.6 to 2.4 mm].
b. 10,000V systems—1/8 in. [3.2 mm].
4. Make sure the leadwires from the flame rod and
ignition electrode are not too close together.
5. Replace any deteriorated leadwires.
6. If the problem cannot be eliminated, the system may
have to be changed to an ultraviolet or infrared flame detec-tion
system.
ULTRAVIOLET SENSOR, IGNITION SPARK
RESPONSE TEST (All Ultraviolet Detectors)
Test to be sure that the ignition spark is not actuating the
FLAME LED:
1. Close the pilot and main burner manual fuel shutoff
valve(s).
2. Start the burner and run through the PILOT IGN
period. Ignition spark should occur, but the flame signal
should not be more than 0.5 Vdc and the FLAME LED should
not turn on.
3. If the flame signal is higher than 0.5 Vdc and the
FLAME LED does come on, consult the equipment Op-
erating Manual and resight the detector further out from the
spark, or away from possible reflection. It may be necessary
to construct a barrier to block the ignition spark from the
detector view. Continue adjustments until the flame signal
due to ignition spark is less than 0.5 Vdc.
NOTE: The Honeywell Q624A Solid State Spark Generator
will prevent detection of ignition spark when properly
applied with the C7027, C7035 or C7044 Minipeeper
Ultraviolet Flame Detectors. The Q624A is only for use
with gas pilots.
RESPONSE TO OTHER ULTRAVIOLET SOURCES
(All Ultraviolet Detectors)
Under certain conditions, an ultraviolet detector will
respond to other ultraviolet sources as if it is sensing a flame.
These ultraviolet sources include artificial light, such as
incandescent or fluorescent bulbs, mercury and sodium
vapor lamps or daylight. To check for proper detector
operation, check the Flame Failure Response Time (FFRT)
and conduct Safety Shutdown Tests under all operating
conditions.
HOT REFRACTORY SATURATION TEST
(All Infrared Detectors)
Test to be sure that radiation from hot refractory does
not mask the flickering radiation of the flame itself.
Start the burner and monitor the flame signal during
the warm-up period. A decrease in signal strength as the
refractory heats up indicates hot refractory saturation. If
saturation is extreme, the flame signal will drop below
1.25 Vdc and the system will shut down as though a flame
failure has occurred.
17
RM7823A
CHECKOUT
65-0106—2