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R4140G, L AND M FLAME SAFEGUARD PROGRAMMING CONTROLS
NOTE: This step requires two people—one to open the
manual valve(s) and one to watch for ignition.
If the main burner flame is not established within five
seconds, or within the normal lightoff time specified by
the burner manufacturer, close the manual main fuel
shutoff valve(s) and open the master switch.
Purge the combustion chamber to remove any
unburned fuel. Check all burner adjustments.
Wait about three minutes. Reset the lockout switch (if
tripped), close the master switch, and let the
programmer recycle to MAIN. Repeat steps
(try lightoff again).
If the second attempt is unsuccessful, adjust the flame
detector position so that a larger pilot is required to hold
in flame relay 2K. This may require relocating the flame
detector to sense farther out on the pilot flame, or
adding an orifice plate.
Measure the pilot flame signal after adjusting the flame
detector to make sure it is stable and above the
minimum (see Table 4).
Repeat steps
through
positively lights with the pilot flame just holding in flame
relay 2K.
Repeat the lightoff of the main burner several times
(steps
through
) with the pilot at turndown.
When the main burner lights reliably with the pilot at
turndown, disconnect the manometer (or gauge) and
turn up the pilot to normal.
If used, remove the bypass jumpers from the low fuel
pressure limits.
Run the system through another cycle to check for
normal operation.
Ignition Interference Test (All Flame Rods)
Test to make certain 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 causes safety shutdown (relay 2K does not pull in
and the programmer acts as though the pilot or main burner, if
using direct spark ignition, was not ignited). If it increases the
flame signal, it could cause relay 2K to pull in when the true
flame signal is below the minimum acceptable value.
To Test for Interference
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 1/2 uA) indicates ignition interference.
To Eliminate Ignition Interference
Make sure there is enough ground area.
Be sure the ignition electrode and the flame rod are on
opposite sides of the ground area.
Check for correct spacing on the ignition electrode:
6,000 volt systems—1/16 to 3/32 in. (1.6 to 2.4 mm).
10,000 volt systems—1/8 in. (3.2 mm).
Make sure the leadwires from the flame rod and ignition
electrode are not too close together anywhere.
Replace any deteriorated leadwires.
If the problem cannot be eliminated, change to an
ultraviolet flame detection system.
60-0770—2
and
until the main burner
Hot Refractory Saturation Test (All Infrared
Detectors)
Test to make certain 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
warmup period. A decrease in signal strength as the
refractory heats up indicates hot refractory saturation. If
saturation is extreme, the flame relay 2K drops out 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 ahead of the cell to restrict the
viewing area. If this does not work, resight the detector at a
cooler, more distant background. You can also try lengthening
the sight pipe or decreasing the pipe size (diameter). Continue
adjustments until hot refractory saturation is eliminated.
Hot Refractory Hold-In Test (Rectifying Photocells or
Infrared Detectors)
Test to make certain that hot refractory does not cause flame
relay 2K to stay pulled-in after the burner flame goes out. This
condition delays response to flame failure and also prevents
a system restart as long as hot refractory is detected.
First check the plug-in flame signal amplifier by starting a
burner cycle. As soon as the programmer stops for the run
period, lower the setpoint of the burner controller to shut
down the burner while the refractory is still at a low
temperature. Measure the time it takes for the flame relay 2K
to drop out after the flame goes out. (Watch or listen to the
flame relay to determine when it drops out.) If the flame relay
fails to drop out within four seconds, open the master switch
and replace the amplifier.
To check rectifying photocells for hot refractory hold-in,
operate the burner until the refractory reaches its maximum
temperature. Then terminate the firing cycle. (Lower the
setpoint of the burner controller, or set the fuel selector switch
to OFF. Do not open the master switch.) Visually observe
when the burner flame goes out. After the flame goes out,
measure the time it takes for the flame relay 2K to drop out.
(Watch or listen to the flame relay to determine when it drops
out.) If the flame relay fails to dropout within four seconds, the
photocell is sensing hot refractory. This condition must be
corrected as described in the last paragraph of this test
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
a flickering infrared radiation; it can reject a steady signal from
hot refractory. 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. Take care when applying an
infrared system to ensure its response to flame only.
To check infrared (lead sulfide) detectors for hot refractory
hold-in, operate the burner until the refractory reaches its
maximum temperature. If the installation has a multifuel
burner, burn the heavier fuel, which is most likely to reflect,
bend, or obscure the hot refractory's steady infrared radiation.
16
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Troubleshooting
