These combination warm air fan and limit controllers are
suitable for various types of forced air heating systems.
The controllers have 2 switches; one which opens the
limit circuit if the plenum temperature exceeds the preset
safety limit; it resets automatically. The other switch turns
the fan on and off. The fan is turned on and off according
to plenum temperature. The L4064R has a special high
temperature range suitable for gravity heating systems.
All models may be used as limit controllers by wiring only
the limit side. Limit contacts are suitable for both line
voltage and low voltage. For low voltage applications, the
brass jumper must be removed.
As the plenum temperature rises, the coiled bimetal
sensing element of the control warps and mechanically
makes the fan contacts (at the FAN ON temperature
setting). During normal operation, the call for heat ends
before the LIMIT setting is reached and the fan contacts
break as the plenum temperature falls and the FAN OFF
setting is reached. If the call for heat continues until the
temperature in the plenum rises to the LIMIT setting, the
bimetal element will mechanically break the limit contacts
and de-energize the heating control circuit.