Honeywell 7800 Series Manual page 40

RM7800E,G,L,M
CHECKOUT
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 refrac-
tory 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 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 satura-
tion is eliminated.
HOT REFRACTORY HOLD-IN TEST
(Rectifying Photocell or All Infrared Detectors)
Test to make certain hot refractory will not delay the
flame detection system response to a flameout. This condi-
tion 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 by lowering the
set point of the operating controller, or set the Fuel Selector
Switch to OFF. Do not open the master switch. Visually
observe when the burner flame or FLAME LED goes out. If
this takes more than 0.8 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 heavier 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 more
than three seconds, the infrared detector is sensing hot
refractory. 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 valve(s) and nozzle(s) even though the fuel valve(s)
are closed. Terminating the firing cycle (instead of
opening the master switch) will allow purging 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 cor-
rect the problem, resight the detector at a cooler, more distant
part of the combustion chamber. While resighting the detec-
tor, be aware that it must also properly sight the flame. For an
infrared detector, try lengthening the sight pipe or decreas-
ing 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.
ULTRAVIOLET SENSOR, IGNITION SPARK
RESPONSE TEST (All Ultraviolet Detectors)
Test to make certain that the ignition spark is not actuating
the FLAME LED.
1. Close the pilot and main burner manual fuel shut-
off valve(s).
2. Start the burner and use the Run/Test Switch to stop the
sequence in the PILOT IGN period. Ignition spark should
occur, but the flame signal should not be more than 0.5 Vdc.
3. If the flame signal is higher than 0.5 Vdc and the
FLAME LED does come on, consult the equipment operat-
ing manual and resight the detector farther 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 C7027, C7035 or C7044 Minipeeper Ultra-
violet Flame Detectors. The Q624A is only for use with
gas pilots.
RESPONSE TO OTHER ULTRAVIOLET SOURCES
Some sources of artificial light, such as incandescent or
fluorescent bulbs, mercury sodium vapor lamps and daylight,
produce small amounts of ultraviolet radiation. Under certain
conditions, an ultraviolet detector will respond to these
sources as if it is sensing a flame. To check for proper detector
operation, check the Flame Failure Response Time (FFRT)
and conduct Safety Shutdown Tests under all operating
conditions.
FLAME SIGNAL WITH HOT COMBUSTION
CHAMBER (All Installations)
With all initial start-up tests and burner adjustments
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.
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