AAON Orion VCCX2 User Manual

91
VCCX2 Controller Technical Guide
Mechanical Failure Alarms
Mechanical Cooling Failure
For units with Fixed Stage Cooling, the Mechanical Cooling
Failure Alarm is generated if the Supply Air Temperature
fails to drop 5 degrees (within a user-adjustable time period)
from the temperature the supply air was at when the cooling
was activated and the Supply Air Temperature is not within 5
degrees of Setpoint. The alarm will be cleared when the Supply
Air Temperature drops the 5 degrees and sets the failure timer
back to zero.
On units with variable capacity compressors (utilizing Refrigerant
System Modules), this alarm is not generated; instead, the user
has to monitor the Compressor Module Alarms for Mechanical
Cooling issues. This alarm is also not generated if using a
modulating chilled water valve.
Mechanical Heating Failure
For units with Fixed Stage Heating, the Mechanical Heating
Failure Alarm is generated if the Supply Air Temperature
fails to rise 5 degrees (within a user-adjustable time period)
from the temperature the supply air was at when the heating
was activated and the Supply Air Temperature is not within 5
degrees of Setpoint. The alarm will be cleared when the Supply
Air Temperature rises the 5 degrees and sets the failure timer
back to zero. If using the Preheat-X Controller, any alarm on
that controller will generate this alarm, also. This alarm is not
generated if using a modulating hot water valve.
Supply Fan Proof of Flow Interlock Alarm
A Proof of Flow switch 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, the
Outdoor Air Damper closes (if it is not congured for Outdoor
Temperature control or Space Control with High Percentage
Outdoor Air), and a Fan Proving Alarm is generated. Fan Proving
needs to be congured for this alarm to occur. There is a 30
second delay for this alarm.
Return/Exhaust Fan Proving Alarm
There are conguration options for Return Fan Proving and
Exhaust Fan Proving Alarms. If the unit is congured for Return
Fan Proving, it is assumed that the Return Fan is wired in parallel
with the supply fan relay. In this case, if the supply relay is
energized, but the Return/Exhaust Fan Proving binary input
on the VCC-X EM1 Module does not see 24 VAC, a Return/
Exhaust Fan Proving alarm will occur. If the unit is congured
for Building Pressure Control of the Exhaust Fan, if the Exhaust
relay is energized, but the Return/Exhaust Fan Proving binary
input on the VCC-X EM1 Module does not see 24 VAC, a Return/
Exhaust Fan Proving alarm will occur.
Dirty Filter Alarm
A dierential pressure switch is used to provide a 24 VAC wet
contact closure to indicate a dirty lter status. A Dirty Filter
Alarm is then generated. Dirty Filter needs to be congured for
this alarm to occur.
Emergency Shutdown 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
VCCX2 and will generate an alarm condition. If an Occupied
relay is congured, it will remain energized. BACnet
®
override
commands are cancelled if the Emergency Shutdown Alarm is
activated.
Failure Mode Alarms
High and Low Supply Air Temperature Alarms
If the Supply Air Temperature rises above the user-adjustable
High Supply Air Temperature Cuto Setpoint, heating will be
immediately deactivated, and a High Supply Air Temperature
Cuto Alarm will be generated. The fan will continue to run. This
mode and alarm will be cancelled if the Supply Air Temperature
falls below the High Supply Air Temperature Cuto Setpoint
by 5 degrees.
If the Supply Air Temperature falls below the user-adjustable
Low Supply Air Temperature Cuto Setpoint, all mechanical
cooling will be immediately deactivated. If, after 10 minutes, the
Supply Air Temperature is still below this setpoint, the fan will be
deactivated, the outside air damper will close, and a Low Supply
Air Temperature Cuto Alarm will be generated. This mode and
alarm will be cancelled if the Supply Air Temperature rises above
the Low Supply Air Temperature Cuto Setpoint by 5 degrees.
High and Low Space Temp Failure
When the Space Temperature rises above the Cooling Mode
Enable Setpoint plus the Control Mode High Alarm Oset
setpoint for 30 seconds, the controller will generate a High
Control Temp Failure Alarm. When the Space Temperature drops
below the Heating Mode Enable Setpoint minus the Control
Mode Low Alarm Oset setpoint for 30 seconds, the controller
will generate a Low Control Temp Failure Alarm. Both oset
setpoints are user-adjustable.
Preheat Low Temperature
This alarm indicates a Leaving Air Temperature Cuto Alarm
condition which is activated if the Controlling Leaving Air
Temperature has dropped below 35ºF for more than 2 minutes.
The alarm will be disabled if after a xed delay period the
Leaving Air Temperature has risen above 35ºF.
SEQUENCE OF OPERATIONS
Mechanical Failure and Failure Mode Alarms

AAON Orion VCCX2 Specifications

General

Brand	AAON
Model	Orion VCCX2
Category	Controller
Language	English