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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 information, see Troubleshoot-

ing 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 temperature

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 automatically

cycles when the internal temperature exceeds the setpoint. For the heater to

operate properly and safely, the cause for the temperature exceeding the

high limit setpoint must be corrected.

The super 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 re-

placed.

Troubleshooting

Continued

Remove plate to

access fan and limit

control assembly.

Circulating Air

High Limit

Super High

Limit

Fan/Blower

Control

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Reznor RA 140 Guide de dépannage Page 46