Orion System RNE Modular Controller - Manual (Page 66)

Zone
Zone
SEQUENCE OF OPERATION
RNE Modular Controller Field Technical Guide 66
Sensor Failure, Mechanical Failure, and Failure Mode Alarms
Sensor Failure Alarms
Supply Air Temperature Sensor Failure Alarm
The Supply Air Temperature Sensor Failure Alarm is generated when the
controller detects an open or short circuit on the Supply Air Temperature
Sensor input. Once the alarm is generated, the unit will be completely
shut down. If a sensor is properly detected after the unit has alarmed,
the alarm will be cleared and the unit will restart operations.
Outdoor Air Temperature Sensor Failure Alarm
The Outdoor Air Temperature Sensor Failure Alarm is generated
when the controller detects an open or short circuit on the Outdoor Air
Temperature Sensor input. When this occurs, the Outdoor Air reading
will be artifi cially set to the half point between the Cooling and Heat-
ing Lockout Setpoints. This will allow the cooling and the heating to
continue operating.
Space Temperature Sensor Failure Alarm
If the Space Sensor is confi gured as the Controlling Sensor (Mode En-
able Sensor) or as the Reset Sensor, and if the controller detects an open
or short circuit on the Space Sensor input, then a Space Temperature
Sensor Failure Alarm is generated. If the Space Sensor is confi gured as
the Controlling Sensor and the Failure Alarm is generated, the unit will
shut down. If the Space Sensor is only confi gured as a Reset Sensor and
the Failure Alarm is generated, the Space Temperature will default to a
value half way between the Heating and Cooling Mode Enable Setpoints,
and the unit will continue to run.
Mechanical Failure Alarms
Mechanical Cooling Failure
The Mechanical Cooling Failure Alarm is generated if the Supply Air
Temperature fails to drop 5 degrees (within a user-adjustable time pe-
riod) from the temperature the supply air was at when the cooling was
activated. The alarm will be cleared when the Supply Air Temperature
drops the 5 degrees and sets the failure timer back to zero. This alarm
does not apply for Modulating Cooling.
Mechanical Heating Failure
The Mechanical Heating Failure Alarm is generated if the Supply Air
Temperature fails to rise 5 degrees (within a user-adjustable time pe-
riod) from the temperature the supply air was at when the heating was
activated. The alarm will be cleared when the Supply Air Temperature
rises the 5 degrees and sets the failure timer back to zero. This alarm
does not apply for Modulating Heating.
Proof of Air Flow Alarm
A Proof of Flow switch (by others) provides a 24 VAC wet contact
closure when the Supply Fan is operating. If this contact opens while
the fan is being called to run, all heating and cooling is disabled, and
a Fan Proving Alarm is generated. Fan Proving needs to be confi gured
for this alarm to occur.
Dirty Filter Alarm
A differential pressure switch (by others) is used to provide a 24 VAC
wet contact closure to indicate a dirty fi lter status. A Dirty Filter Alarm is
then generated. Dirty Filter needs to be confi gured for this alarm to occur.
Emergency Shutdown (Smoke) Alarm
A 24 VAC wet contact input is available to be used when a N.C. Smoke
Detector, Firestat, or other shutdown condition occurs. If this contact
opens, it will initiate shutdown of the SA and will generate an alarm con-
dition. This contact closure does not produce an instantaneous shutdown.
Emergency Shutdown needs to be confi gured for this alarm to occur.
For instantaneous shutdown, the device initiating the open condition
on this contact should also be wired to cut the 24 V common to the SA
relay outputs.
Failure Mode Alarms
High and Low Supply Temp Alarm
These alarms are activated when the Supply Air Temperature (SAT)
rises above the High Cutoff Temperature Setpoint (immediate) or drops
below the Low Cutoff Temperature Setpoint (for 10 minutes). Both
cutoff setpoints are user-adjustable. This mode shuts off the unit (with
a 3 minute fan off delay) until the mode is cancelled.
This mode is cancelled when the SAT drops 5 degrees below the High
Cutoff Temperature Setpoint or rises 5 degrees above the Low Temp
Cutoff Temperature Setpoint, or when the unit changes back into Oc-
cupied Operation.
High and Low Control Temp Failure
These alarms only apply when Space or Return Air is confi gured ad the
Mode Enable Sensor.
When the Controlling Sensor Temperature rises above the Cooling Mode
Enable Setpoint plus the Control Mode High Alarm Offset setpoint, the
controller will generate a High Control Temp Failure Alarm.
When the Controlling Sensor Temperature drops below the Heating
Mode Enable Setpoint minus the Control Mode Low Alarm Offset set-
point, the controller will generate a Low Control Temp Failure Alarm.
Both offset setpoints are user-adjustable.
Module Alarm
This alarm applies to any E-BUS Module communicating with the RNE
Controller. The E-BUS modules include the Full Digital Module, the
Two Condenser Head Pressure II Module, and the Water Source Heat
Pump Module. If any of these modules stop communicating with the
RNE Controller or if there is an alarm on one of these modules, this
Module Alarm will be generated.