Prepurge runs the fan with dampers open long enough to replace the furnace and flue gas volume several times, so any leaked fuel is diluted and removed before a spark is struck. Commercial burners commonly purge for 30 seconds to a few minutes at high fire air flow, proven by an air switch and damper position switch. Postpurge clears the furnace after the flame goes out. In hydronics, purge also means pushing air out of piping with water.
Don't jumper the high fire switch to skip the purge, that's the one minute that keeps the boiler in one piece.
Short-cutting purge to get heat faster is one of the most dangerous shortcuts in a boiler room.
Also heard as
- purge cycle
Related terms
Flame safeguard
The control that runs a burner's start sequence, watches the flame, and shuts the fuel off fast if the flame fails.
Trial for ignition
The short, fixed time window during which the burner control must see a pilot or main flame before it locks out.
Low-fire start
The rule that a burner must light off at its minimum firing position, proven by a switch, before increasing rate.
Puffback
A small explosion of oil vapor in the combustion chamber that blows soot and smoke out of the burner and into the room.
Same word, different worlds
To pump fresh grease into a bearing until the old grease is pushed out of the relief port or seal.
AdhesivesTo run adhesive through a mixer or dispense valve and discard it, clearing old, unmixed or off-ratio material.
Welding, Brazing & NDEInert gas flowed inside a pipe or behind a joint to keep the back of the weld from oxidizing.