Honeywell 7800 Series Manual page 18

RM7823A
CHECKOUT
If hot refractory saturation occurs, the condition must be
corrected. Add an orifice plate in front of the cell to restrict the
viewing area. You can also try to lengthen the sight pipe or
decrease the pipe size (diameter). Continue adjustments until
you eliminate hot refractory saturation.
HOT REFRACTORY HOLD-IN TEST
(Rectifying Photocell or All Infrared Detectors)
Test to be sure hot refractory will not delay the flame
detection system response to a flameout. This condition can
delay response to flame failure and also can prevent a system
restart as long as hot refractory is detected.
To check rectifying photocells for hot refractory hold-in,
operate the burner until the refractory reaches its maximum
temperature. Then terminate the firing cycle. Do not open the
master switch. Visually observe when the burner flame or
FLAME LED goes out. If this takes longer than .8 or 3
seconds (depending on the FFRT of the amplifier), 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 refrac-
tory 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 apply-
ing an infrared system to verify its response to flame only.
To check infrared (lead sulfide) detectors for hot refrac-
tory hold-in, operate the burner until the refractory reaches its
maximum temperature. If the installation has a multi-fuel
burner, burn the heaviest fuel that is most likely to reflect,
bend or obscure the hot refractory steady infrared radiation.
When the maximum refractory temperature is reached, close
all manual fuel shutoff valve(s) or open the electrical circuits
of all automatic fuel valve(s). Visually observe when the
burner flame or FLAME LED goes out. If this takes longer
than three seconds, the infrared detector is sensing hot
refractory. Immediately terminate the firing cycle. Do not
open the master switch.
NOTE: Some burners continue to purge their oil lines be-
tween the valve(s) and nozzle(s) even though the fuel
valve(s) is closed. Terminating the firing cycle (instead
of opening the master switch) will allow purging 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, the condition
must be corrected. Add an orifice plate in front of the cell to
restrict the viewing area of the detector. If this does not
correct the problem, resight the detector at a cooler, more
65-0106—2
distant part of the combustion chamber. While resighting
the detector, be aware that it must also properly sight the
flame. When using an infrared detector, you can also 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.
FLAME SIGNAL WITH HOT COMBUSTION
CHAMBER (All Installations)
After all initial start-up tests and burner adjustments are
completed, operate the burner until the combustion chamber
is at the maximum expected temperature. Observe the equip-
ment manufacturer warm-up instructions. Recycle the
burner under these hot conditions and measure the flame
signal. Check the pilot alone for non-DSI applications or the
main burner flame for DSI applications.
Also check the FFRT. Lower the set point of the operat-
ing controller and observe the time it takes for the burner
flame to go out. This should be within .8 or 3 seconds
maximum depending on the amplifier selected.
If the flame signal is too low or unsteady, check the flame
detector temperature. Relocate the detector if the temperature
is too high. If necessary, realign the sighting to obtain the
proper signal and response time. If the response time is still
too slow, replace the Plug-in Flame Signal Amplifier. If the
detector is relocated or resighted, or the amplifier is re-
placed, repeat all required Checkout tests.
SAFETY SHUTDOWN TESTS
(All Installations)
Perform these tests at the end of Checkout after all other
tests have been completed.
1. Loss of flame during RUN.
a. Open the main fuel manual shutoff valve(s). The
manual pilot shutoff valve(s) must also be opened.
b. Start the system. Startup should be normal and the
burner(s) should light normally.
c. After the system sequence is in the normal RUN
period for at least ten seconds, close the manual fuel
shutoff valve(s) to extinguish the burner flame.
d. The flame signal should drop below 1.25 Vdc
within .8 or 3 seconds (depending on the FFRT of
the amplifier) after the main flame goes out.
e. The loads should switch and respond as the equip-
ment manufacturer has specified.
IMPORTANT:
1. If the RM7823A fails to shut down on these tests, take
corrective action (refer to Troubleshooting, RM7823A
System Diagnostics, and return to the beginning of all
Checkout tests).
2. When all Checkout tests have been completed, reset
all switches to original states.
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