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Pilot turndown test
This test is intended to check that the flame is reliably transferred to the main burn-
er when the flame detector detects the pilot flame, even if gas pressure and air pres-
sure change to their worst conditions.
Handling Precautions
• If a fuel pressure limit switch is used, and its contacts are open, turn it
ON with a jumper cable during this test.
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Test procedure
(1) Turn the operation switch OFF.
(2) Close the manual valves to stop the gas supply to the pilot burner and main
burner.
(3) Open the manual valve to the pilot burner.
(4) Turn the power switch ON, and then turn the start switch on, and press and hold
the ignition switch. The pilot will ignite and the pilot valve will open. Ignition
will begin and the combustion lamp will light. Release the ignition switch.
Chapter 3. ADJUSTMENTS FOR TRIAL OPERATION
WARNING
Do not allow the pilot or main burner "Safety Time" (ignition trial time) to
exceed the specifications of the burner or equipment manufacturer. If they
do, fuel may accumulate in the combustion chamber and form an explosive
air-fuel mixture, resulting in a serious explosion hazard.
Carry out the pilot turndown test carefully. If the flame detector is set so that it
detects a pilot flame that is too small to ignite the main burner, this device will
not be able to detect a flame failure in the main burner. In that case, fuel will
continue to be supplied, causing a serious explosion hazard.
Before the pilot turndown test or ignition spark response test, make sure that
all manual fuel valves are closed.
If the pilot turndown test must be carried out repeatedly, completely shut
down all equipment each time the test is finished, and completely discharge
unburned gas or fuel that has accumulated in the ducts and combustion
chamber. Failure to discharge unburned gas or fuel may result in an
explosion.
When the pilot turndown test is complete, turn OFF the power switch to shut
down the power. Restore all test jumpers and limit interlock/regulator settings
to their previous states. If operation begins without the above steps, damage
to the equipment, gas leak or explosion may result.
CAUTION
Only an experienced technician who has knowledge and technical skills
related to combustion equipment and combustion safety should carry out the
pilot turndown test.
