Form I-RA/D 140/235 (Version A), Page 46
Fan and Limit Controls
Model RA/RAD 140 and 235 heaters are equipped with a fan control
and limit control assembly consisting of a specially designed control
mounting bracket with a fan control, a circulating air high limit control,
and a super high limit control attached. To access the fan and limit
control assembly, remove the plate as illustrated. For service informa-
tion, see Troubleshooting Chart 6, page 45.
The main functions of the
fan/blower control
are to provide:
• Delay of fan or blower operation, preventing circulation of cold
air at startup.
• Continued fan or blower operation as long as the unit temper-
ature is above minimum setting. The fan/blower control also
provides additional safety control by keeping the fan or blower
in operation in the event that a malfunction would cause the
oil burner to continue to fire when the thermostat is satisfied.
The
circulating air high limit switch
is nonadjustable and automati-
cally cycles when the internal temperature exceeds the setpoint. For
the heater to operate properly and safely, the cause for the tempera-
ture exceeding the high limit setpoint must be corrected.
The s
uper high limit switch
provides redundant control and is
calibrated to open at a much higher temperature (350°F) than the
standard automatic reset limit switch indicates a major failure caused
by a malfunction of the primary safety controls or miswiring. Before
attempting to re-start the heater the cause must be corrected and the
fan and limit control assembly replaced.
Troubleshooting
Continued
Remove plate
to access fan
and limit control
assembly.
Circulating Air
High Limit
Super High
Limit
Fan/Blower
Control
