7800 SERIES RELAY MODULES
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 recommended 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 .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
b.10,000V
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 warmup 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.
Hot Refractory
(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 maximum temperature (Infrared Only).
If the installation has a
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 setpoint 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 combustion 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 condition 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
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