Igniters
Igniters provide proven ignition energy to immediately light-off the burner. They are permanently installed. Igniters are classified as follows by NFPA:
- Class 3 special: High energy igniter (HEI) capable of directly igniting the main burner fuel. Generally consists of a spark-rod, and power pack to deliver the high voltage pulse train, and required cabling. Operation time of igniter is no longer than required to light-off burner, within maximum allowed trial-for-ignition time.
- Class 3: Low capacity igniter applied particularly to gas and oil burners. Ignites the fuel input to the burner under prescribed light-off conditions. The range of class 3 igniters generally do not exceed 4 percent of full load burner input. Operation time of igniter is not longer than required to light-off the burner, within the maximum allowed trial-for-ignition time.
- Class 2: Medium capability igniter applied particularly to gas and oil burners to ignite the fuel input to the burner under prescribed light-off conditions. The range of class 2 igniters generally is 4 to 10 percent of full-load burner input. Class 2 igniters may remain in operation to support ignition under low-load or adverse operating conditions. Class 2 igniters cannot be used to extend main burner turn-down range.
- Class 1: High capacity igniter used to ignite the fuel input through the burner. Supports ignition under any burner light-off or operating conditions. Its location and capacity provide sufficient ignition energy at its associated burner to raise any credible combination of burner inputs of both fuel and air above the minimum ignition temperature. Tests are to be performed with this ignition system in service to verify that the igniter furnished meets the requirement of this class as specified in its design. Class 1 igniters can be used to extend the main burner’s turndown, where they are in service and flame if proved.
