AAON VCCX2 User Manual

37VCCX2 Controller Technical Guide
SEQUENCE OF OPERATIONS
Modes of Operation
Heat Pump Adaptive Defrost Operation
The adaptive defrost operation adjusts the time interval (adaptive
defrost timer) in between Defrost Mode cycles.
The unit will leave the Defrost Mode after 10 minutes have elapsed
or the defrost coil temperature switch opens. If the defrost cycle is
terminated because the 10 minute timer runs out, the adaptive defrost
timer value will be subtracted from the original defrost interval.
If the defrost cycle is terminated between the eighth and ninth
minute, the defrost interval will not be changed.
If the defrost cycle is terminated before the eighth minute, this
could be an indicator that the unit may need less defrost time.
To address this issue, the adaptive defrost timer value will be
inversely proportionally added to the original defrost interval as
the termination time moves from eight minutes to zero minutes.
Adaptive defrost can be disabled by setting the adaptive defrost
timer setpoint to zero.
Water Source Heat Pump Operation
A reversing valve relay output can be congured to activate with the
rst compressor stage in the Heating Mode or the Cooling Mode
of operation.
In Heating Mode, auxiliary heat can be used with compressor heat
to achieve the active Supply Air Heating Setpoint. Auxiliary heat
can be:
• Modulating heat
• Staged forms of heat
• A modulating form of heat followed by staged heat
When auxiliary heat comes on in conjunction with a digital
compressor heat stage, the digital compressor will be locked at
100% until the supply air temperature rises above the Supply Air
Temperature Heating Setpoint plus the heat staging window. At that
point, the auxiliary heat will stage o (after a stage- down delay)
and the digital compressor heat will be allowed to modulate.
There is no Defrost Mode on a water source heat pump unit.
The unit can be congured for a percentage of glycol. The options
are 0%-40% in 5% increments.
Warm-Up Mode/Cool-Down Mode
Morning Warm-Up Mode Operation
NOTE: Morning Warm-Up can be configured for any
application but should not be used on 100% outdoor
air units, since the outdoor air damper remains closed
during warm-up.
When the VCCX2 Controller is congured for Morning Warm-Up
and switches to the Occupied Mode of Operation (not Override or
Force Mode from an operator interface device), the unit compares
the return air temperature to a Morning Warm-Up target temperature.
If the return air temperature is below this setpoint, the Warm-Up
Mode is initiated. Heating will then be controlled to the Warm-Up
Supply Air Temperature Setpoint.
This mode remains in eect until the return air temperature rises
above the target temperature or a user-adjustable time period
expires. Warm-Up Mode is not initiated by push-button overrides
or unoccupied heating demands. The outdoor air damper remains
closed during Warm-Up Mode.
Once the Warm-Up Mode has been terminated, it cannot resume
until the unit has been through a subsequent Unoccupied Mode.
Only one Warm-Up Mode is allowed per Occupied cycle.
If stand-alone VAV boxes that need to be forced wide open during
the Warm-Up Mode, congure one of the relay outputs to be used
during this Mode. If the Warm-Up Mode is active, the relay is
activated. This relay then becomes the Force Open Command for
all VAV boxes to which it is wired.
Morning Cool-Down Mode Operation
When the VCCX2 Controller is congured for Morning Cool-
Down and switches to the Occupied Mode of Operation (not
Override or Force Mode from an operator interface device), the unit
compares the return air temperature to a Morning Cool-Down target
temperature. If the return air temperature is above this Setpoint, the
Cool-Down Mode is initiated. Cooling will then be controlled to
the Cool-Down Supply Air Temperature Setpoint.
This mode remains in eect until the return air temperature drops
below the target temperature or a user-adjustable time period
expires. Cool-Down Mode is not initiated by push-button overrides
or unoccupied cooling demands. The outdoor air damper remains
closed during Cool-Down Mode.
Once the Cool-Down Mode has been terminated, it cannot resume
until the unit has been through a subsequent Unoccupied Mode.
Only one Cool-Down Mode is allowed per Occupied cycle.
If stand-alone VAV boxes that need to be forced wide open during
the Cool-Down Mode, congure one of the relay outputs to be used
during this mode. If the Cool-Down Mode is active, the relay is
activated. This relay then becomes the Force Open Command for
all VAV boxes to which it is wired.

AAON VCCX2 Specifications

General

Brand	AAON
Model	VCCX2
Category	Controller
Language	English