Low Limit Snap Discs F-120: 3/4 in diameter air stream
F-120 - 3/4" diameter air stream mount auto manual reset for pellet stoves.
These switches are used to shut off fans only when the stove has completely cooled so all the warm air leaves the stove. It also keeps the auger going when the stove has warmed up (proof of fire). If there is no proof of fire the stove shuts down for safety.