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12. Close the master switch to recycle the burner and stop
the sequence in the PILOT period by using the
Run/Test Switch.
13. Increase the pilot flame size by increasing its fuel flow
until a smooth main flame is accomplished.
14. Reposition the flame scanner sight tube or use orifices
until the pilot flame signal voltage is in the range of 1.25
to 1.50 Vdc.
15. When the main burner lights reliably with the pilot at
turndown, disconnect the manometer (or pressure
gauge) and turn up the pilot gas flow to that recom-
mended by the equipment manufacturer.
16. If used, remove the bypass jumpers from the subbase
terminals, limits/controls, or switches.
17. Run the system through another cycle to check for
normal operation.
18. Return the system to normal operation.
IGNITION INTERFERENCE TEST (ALL
FLAME RODS)
Ignition interference can subtract from (decrease) or add to
(increase) the flame signal. If it decreases the flame signal
enough, it causes 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 0.5 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. 6000V 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, consider changing
the system to an ultraviolet flame detection system.
Hot Refractory Saturation Test
(All Infrared Detectors)
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 drops below 1.25 Vdc and the
system shuts down as though a flame failure occurred.
If hot refractory saturation occurs, the condition must be corrected.
Add an orifice plate in front of the cell to restrict the viewing area,
lengthen the sight pipe or decrease the pipe size (diameter).
Continue adjustments until hot refractory saturation is eliminated.
R7120M 7800 SERIES RELAY MODULES
Hot Refractory Hold-in Test (Rectifying
Photocell, Infrared Detectors, Ultraviolet
Detectors)
This condition can delay response to flame failure and also
can prevent a system restart if hot refractory is detected.
Infrared (lead sulfide) detectors can respond to infrared rays
emitted by a hot refractory, even when the refractory has
visibly ceased to glow. Infrared radiation from a hot refractory
is steady, but radiation from a flame has a flickering
characteristic. The infrared detection system responds only to
flickering infrared radiation; it can reject a steady signal from
hot refractory. The refractory 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 verify its response to flame only.
The ultraviolet detector can respond to hot refractory above
2300°F (1371°C).
1. Operate the burner until the refractory reaches its maxi-
mum temperature (infrared only). If the installation has a
multi-fuel burner, burn the heavier fuel that is most likely
to reflect, bend or obscure the hot refractory steady
infrared radiation.
2. When the maximum refractory temperature is reached,
close all manual fuel shutoff valves, or open the electrical
circuits of all automatic fuel valves.
3. Visually observe when the burner flame or FLAME LED
goes out. If this takes more than three seconds, the
infrared detector is sensing hot refractory.
4. Immediately terminate the firing cycle. Lower the set-
point to the operating controller, or set the Fuel Selector
Switch to OFF. Do not open the master switch.
NOTE: Some burners continue to purge oil lines between
the valves and nozzles even though the fuel valves
are closed. Terminating the firing cycle (instead of
opening the master switch) allows purging the com-
bustion chamber. This reduces a buildup of fuel
vapors in the combustion chamber caused by oil line
purging.
5. If the detector is sensing hot refractory, correct the con-
dition by one or more of the following procedures:
a. Add an orifice plate in front of the cell to restrict the
viewing area of the detector.
b. Resight the detector at a cooler, more distant part of
the combustion chamber. Make sure the detector
properly sights the flame.
c. Try lengthening the sight pipe or decreasing the
pipe size (diameter).
For details, refer to the detector Instructions and the
equipment Operating Manual. Continue adjustments until hot
refractory hold-in is eliminated.
IGNITION SPARK RESPONSE TEST
(ALL ULTRAVIOLET DETECTORS)
Test to make certain that the ignition spark is not actuating the
FLAME LED:
15
66-1193EF—01
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