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RPB-IOM (06-22) 131782-B
Pilot and Ignition Systems
⚠ WARNING ⚠
Due to high voltage on the pilot spark wire and pilot electrode, do not touch when energized.
• Pilot: The horizontal pilot is located in the control end of the burner rack (see Figure 16) and is accessible after
the control compartment panel has been removed. All pilots are target type with lint-free feature. Pilot gas pressure
should be the same as supply line pressure (refer to Gas Supply Pressure section). If required, adjust the pilot
flame length to approximately 1-1/4 inch using pilot adjustment screw in control valve body.
Figure 16. Typical Burner Rack with Spark Pilot
• Intermittent spark ignition safety pilot systems: There are two types of intermittent spark pilots: one type shuts
off the pilot gas flow between the cycles and the other not only shuts off the pilot gas flow between cycles but
also has a lockout device that stops the gas flow to the pilot if the pilot fails to light in 120 seconds. This lockout
feature has a 1-hour retry or requires manual reset by interruption of the thermostat circuit. Propane units installed
in Canada require the spark ignition system with the lockout device. Refer to the wiring diagram supplied with the
heater for pilot system identification and wiring. Spark pilot without lockout is designated as option AH2 or with
lockout is option AH3.
• Ignition controller: As part of the intermittent safety pilot system, the ignition controller provides high voltage
spark to ignite pilot gas and also acts as the flame safety device. After ignition of the pilot gas, the ignition controller
electronically senses the pilot flame. A low voltage DC electrical signal is imposed on the separate metal probe
in the pilot assembly. The metal probe is electrically insulated from ground. The pilot flame acts as a conduction
path to ground to complete the DC circuit and prove pilot flame. Proper operation of the electronic spark ignition
system requires a minimum flame signal of 0.2 microamps, as measured by a microampmeter. With pilot flame
proven, the ignition controller energizes the main gas valve.
Burners and Carryover System
• Burners: These duct furnaces have individually-formed steel burners with accurately die-formed ports to provide
controlled flame stability without lifting or flashback with either natural or propane gas. All burners are lightweight
and are factory-mounted in an assembly that permits all of the burners to be removed as a unit for inspection or
service.
NOTE: Natural gas burner racks (except when equipped with electronic modulation option AG39
or AG40) are equipped with two flash carryovers. Propane gas burners are equipped with one flash
carryover and a regulated gas lighter tube system.
• During regular service, check the main burner ports, the carryover assemblies, and the orifices for cleanliness.
Flash Carryover
Main
Burner
Spark Pilot
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