AAON VCCX2 User Manual

48VCCX2 Controller Technical Guide
Mechanical Failure Alarms
Mechanical Cooling Failure
Fixed Stage Cooling: The mechanical cooling failure alarm is
generated if the supply air temperature is more than 5°F from the
Supply Air Temperature Setpoint at the activation of stage 1 of
cooling and subsequently fails to change by more than 5°F within
the user-adjustable failure time period. If the supply air temperature
subsequently changes by more than 5°F from that original supply
air temperature, the alarm timer will be reset and the alarm will
be cleared.
This alarm is not utilized for RSM based cooling systems or for
modulating chilled water systems.
Variable Capacity Compressors (utilizing RSMs): This alarm is not
generated; instead, the user has to monitor the compressor module
alarms for mechanical cooling issues.
Mechanical Heating Failure
Fixed Stage Heating: The mechanical heating failure alarm is
generated if the supply air temperature is more than 5°F from the
Supply Air Temperature Setpoint at the activation of stage 1 of
heating and subsequently fails to change by more than 5°F within
the user-adjustable failure time period. If the supply air temperature
subsequently changes by more than 5°F from that original supply
air temperature, the alarm timer will be reset and the alarm will
be cleared.
Any alarm on a MODGAS-X series module will cause this alarm to
activate. This alarm is not utilized for modulating systems including
modulating hot water systems or SCR electric heat.
Fan Proving Failure
A proof of ow 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.
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 lter alarm
is then generated. Dirty lter 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 normally
closed 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 canceled
if the emergency shutdown alarm is activated.
Relay Runtime Exceeded
Alarm is generated if a Relay Run Time exceeds the user adjustable
time.
Economizer Feedback Missing
This failure can only occur during calibration and won’t clear until
the feedback issue is corrected and it is recalibrated (cycle power
to the unit). The Missing Feedback will cause B, C, D, E alarms.
Title 24 Alarm “A” (Economizer Air Temperature Sensor
Failure)
Outside air or Supply Air Temperature Sensor is shorted or missing.
Title 24 Alarm “B” (Not Economizing When it Should)
Economizer is enabled but not following the desired economizer
position commanded.
Title 24 Alarm “C” (Economizing When It Should Not)
Economizer is not enabled but the feedback signal indicates a
position more open than the minimum.
Title 24 Alarm “D” (Economizer Damper Not
Modulating)
Economizer is enabled but not within 10% of desired position
within 150 seconds.
Title 24 Alarm “E” (Economizer Excess Outdoor Air
Failure)
Economizer feedback is lost or economizer is not following
commanded position.
Return/Exhaust Fan Proving Failure
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 fan 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.

AAON VCCX2 Specifications

General

Brand	AAON
Model	VCCX2
Category	Controller
Language	English