Heat King IDF1000 Operation Manual page 17

Protective devices
The IDF1000 is equipped with the following protective devices
to protect the user:
E-STOP
The emergency stop switch is monitored by the controller inputs. The input is connected to ground
when the switch is pressed. In the event of an e-stop condition the system mode is set to OFF and all
output functions are shut down by the controller.
MECHANICAL TEMPERATURE LIMITS
Two bi-metal thermostats are used in series to disable / lockout the burner and generate an alarm:
1. 87°C (190°F) Auto-Reset Type
2. 110°C (230°F) Manual Reset Type
All thermostats are physically mounted in the leaving air stream and wired to electrically disable the
burner in the event of an over temperature condition. The controller monitors the status of these limits
and generates a "Mechanical Temp Limit" alarm. This alarm condition will result in the unit being put
into STANDBY mode. The operator would then be required to acknowledge the alarm condition and
put the unit back into AUTO mode. Under normal operating conditions these alarms should not be
triggered. Refer to page 33 for more information on alarms.
DIFFERENTIAL PRESSURE SWITCH
Used as feedback to verify that the centrifugal clutch is engaged and the Fan is operating. The pres-
sure switch contains a normally open contact that closes when pressure is present which indicates
the fan is running. During AUTO mode operation, this signal is monitored and used to put the unit
into STANDBY if the contact has not closed after 15 seconds. It will then remain in STANDBY until the
alarm is acknowledged and the system put back into AUTO mode by the operator.
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