A good light-off is quiet and immediate: spark, pilot, main flame, no puff. A hard light-off comes with a thump, a puff of flue gas out of the inspection ports, or a shudder through the breeching, and means fuel accumulated before it lit. Causes include delayed spark, low pilot, wrong low-fire position or too much fuel at ignition, and repeated hard light-offs crack refractory and loosen tubes.
Every light-off on number three comes with a bang you can feel in your chest, nobody leaves until we find out why.
Also heard as
- lightoff
- light off
Related terms
Low-fire start
The rule that a burner must light off at its minimum firing position, proven by a switch, before increasing rate.
Trial for ignition
The short, fixed time window during which the burner control must see a pilot or main flame before it locks out.
Puffback
A small explosion of oil vapor in the combustion chamber that blows soot and smoke out of the burner and into the room.
Pilot
A small flame that lights the main burner and is often used to prove ignition before main fuel flows.