Installation/Lighting | Gas Pilots
PIPING SCHEMATIC
mixer gas cartridge with mixer adjustment screw
pilot flame
air
mixture pressure
air pressure
air valve
impulse line
pilot mixer
pilot tip
gas
5D
gas valve
pilot regulator (recommended accessory)
INSTALLATION
LIGHTING
1. Pilot air supply must be at constant pressure, i.e. taken from main air manifold between combustion air blower and main air control valve. 2. Pilot gas supply must be taken upstream of main gas regulator and shutoff valves. It may be necessary to install a pressure reducing regulator in the pilot gas line. 3. 7218 Pilot Gas Regulators must be mounted with spring housing down. 7350 Pilot Gas Regulators may be mounted in any position. 4. To avoid problems caused by dirt in the pilot tip, install main burner so pilot port is located between 9 and 3 o'clock, (above the horizontal Centerline). 5. While pilot tip may be screwed directly into its mixer, a minimum of 5 pipe diameters is recommended between mixer and tip. If there is an elbow between mixer and tip, there must be 5 pipe diameters straight pipe between elbow and tip. 6. Use hi-temp anti-seize compound on threaded pilot tips and hand tighten into burner. Lightly wrench tighten only if firing against abnormally high positive pressure. 7. When installing pilot tip, orient spark plug or lighter hole so it is easily accessible. 8. Installation of a union between mixer and tip will facilitate removal of tip for cleaning. PRESSURE REQUIREMENTS 1. Minimum recommended air pressure at pilot mixer inlet is 4.0 osi/7.0"w.c./17.2 mbar. 2. Minimum gas pressure at pilot regulator inlet for a cross- connected system should be 2 osi/3.5"w.c./8.6 mbar higher than loading pressure (air or air/gas mixture). 3. Minimum gas pressure at pilot regulator inlet for an atmospheric (zero gas pressure) system is 2 osi/3.5"w.c./8.6 mbar).
1. Close all manual pilot and main gas supply valves. 2. Make sure all fans and blowers are running and combustion chamber has been purged with a minimum of (4) changes of atmosphere. 3. Adjust main burner's air control valve for low fire air pressure (if applicable). 4. Set air pressure to the pilot mixer inlet at 6-8 osi/10-14"w.c./26-34 mbar above combustion chamber pressure. This will result in a 3-4"w.c. (7.5-10 mbar) mixture pressure aft er pilot is lit. 5. Make sure pilot mixer gas adjustment is fully closed (CW). 6. Energize ignition and pilot gas solenoid valve. 7. Open pilot gas cock. 8. Counting the number of turns, slowly open (CCW) mixer adjustment, noting setting at which pilot initially lights. 9. Continue opening adjustment until pilot flame becomes unstable, losing its sharp inner cone. 10. Return valve to a position midway between settings determined in steps 8 and 9. 11. De-energize ignition to make sure pilot remains stable without spark. Readjust if necessary. 12. Energize ignition and pilot solenoid simultaneously several times to verify repeatable ignition. TROUBLESHOOTING NOTES 1. The spark igniter may light the pilot better if the ground electrode is bent 45° resulting in a 0.09"-0.10" (2.5 mm) gap. 2. If pilot will not light, check for spark at the plug and gas at the mixer. If both are present, remove and clean pilot tip. Make sure all piloting ports are clean: Plugging of one hole can prevent lighting.
Bulletin 4015/4025 Page 5
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