PILOT SYSTEMS
PILOT ADJUSTMENT
1. Before lighting any pilot, make sure the furnace has been adequately purged . This requires operating the main air blower long enough to prove at least 4 air changes before ignition. Example: A 4' x 5' x 10' furnace (200 cu ft volume) has a blower designed to provide 460 cfm at highest input. It should be run (air flow proven at 460 cfm) for at least (4 x 200 divided by 460) = 1.74 minutes air purge time. 2. Adjust the pilot air valve for the required pilot air pressure, generally 6 to 8 osi at the 1/8 " air pressure tap in the pilot mixer air connection. 3. Starting from a fully closed position, open the pilot mixer gas adjusting screw about 4 turns (counterclockwise). 4. Energize both the ignition spark transformer and the pilot gas solenoid valve. Spark plug gap should be 0.90 to 0.100." If the pilot does not light, turn the gas adjusting screw in or out as required, until ignition occurs. 5. FINE-TUNE THE PILOT FOR BEST FLAME STABILITY as follows: First , turn the gas adjusting screw clockwise until the pilot flame goes out. This is the "lean limit." Next , counting the number of turns from the lean limit, turn the gas adjusting screw counterclockwise, lighting the pilot, and continuing until the rich limit is reached, ragged flame appearance* and loss of the sharp inner cone. Then , having counted the number of turns from lean to rich limit (generally 1 to 2 times), set the gas adjusting screw at mid-point between the limits. This will result in a condition near correct air/fuel ratio. 6. Slowly turn the pilot air pressure down to 1.0 osi. If the flame appears to go off ratio,* remove the pilot regulator adjusting cap and adjust the pilot gas regulator spring until the flame looks correct. Turning the regulator spring adjusting screw clockwise increases the gas flow; counterclockwise decreases gas flow. Replace the cap. Turn the pilot air pressure back up to its original setting. 7. With 6 to 8 osi pilot air pressure, the mixture pressure at the 1/8 " pressure tap on the mixer discharge should be 3 to 4"w.c. when the flame is burning (mixture pressures are valid only if measured when burning). KEEP RECORDS - page 63.
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