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Chapter 5. Trial Operation and Adjustment
Ignition spark response (ultraviolet sensor)
WARNING
Ensure that the ultraviolet sensor does not detect ultraviolet rays other than those from the burner.
If the sensor detects other ultraviolet rays, it will continue to send flame detection signals even if
the burner flame goes out. Consequently, fuel will continue to be supplied, potentially resulting in
an explosion.
Before doing the spark response test, make sure that all manual fuel valves are closed.
(1) Close the manual valves in the piping for the pilot and main burners.
(2) Begin operation and measure the flame voltage during the ignition trail
sequence to check for any effect from the ignition spark.
(3) If the spark has an effect, such as causing the FLAME LED to light up, make
adjustments using the following methods.
•
Move the ultraviolet sensor or the ignition spark rod so that the spark does
not affect the flame voltage.
•
Attach a shield that prevents the spark's ultraviolet radiation from entering
the optical path of the ultraviolet sensor. Adjust so that the spark's effect on
the flame signal is 0.4 V DC or less.
•
If the S7200A___GH_ or S720A___GH_ igniter is used, swap the polarity
of the power to the igniter. When this device is used in combination with an
igniter, changing the polarity of the power can prevent the ultraviolet sensor
from detecting the spark.
Note: “_” represents a number.
Handling Precautions
• Ensure that the ultraviolet sensor does not detect ultraviolet rays other than
those from the burner flame.
Sources of ultraviolet radiation (other than the burner flame) that can activate the
ultraviolet sensor include the following.
Examples:
Ultraviolet ray sources
1371 °C or hotter red-hot furnace wall (within 50 cm from wall)
Ignition transformer, welding arc spark
Gas laser
Sun lamp
Germicidal lamp, ultraviolet lamp, fluorescent lamp
Strong flashlight
Gamma ray and X-ray
sources
X-ray analyzer, gamma ray analyzer/measurer
Electron microscope
X-ray machine
High-voltage vacuum switch
High-voltage capacitor
Radioactive isotope
Any other ultraviolet, gamma, or X-ray source
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