iWorx® VPU2
505-010-2, Effective: April 29, 2014
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© 2014 Taco Electronic Solutions, Inc.
Filter Status
The filter status input is monitored to determine if the filter is operating properly. The input is used to indicate that main-
tenance is required on the filter. The unit is not shut down due to a filter alarm.
Indoor Air Quality
An indoor air quality input is provided. If an indoor air quality alarm is indicated while the space is occupied, the supply
air fan is energized and the economizer is overridden to supply fresh air to the space. The source of an indoor air qual-
ity signal can be a digital sensor providing an on/off signal or a configurable analog sensor.
Setup of the analog sensor requires the IAQ sensor settings to be populated. A Min, Max, Setpoint, and Offset can be
specified.
When an indoor air condition is sensed by the controller, the economizer is opened to 100%. If the mixed air tempera-
ture drops too low, the economizer modulates in an attempt to maintain the IAQ MAT setpoint while still allowing fresh
air into the system.
The controller has a temperature reset function for IAQ alarm operation. The temperature reset function allows the
space temperature to rise above or drop below the calculated control setpoints by a configurable amount. During IAQ
Alarm operation, if the space temperature rises above or drops below the temperature reset limit, the controller
resumes normal economizer control to maintain a comfort space temperature. Once the space temperature is brought
within the calculated setpoints and an IAQ Alarm condition still exists, the controller resumes the IAQ mode of opera-
tion.
The controller has a configurable alarm delay function. This function allows the controller to attempt to clear the IAQ
condition with the economizer before triggering an alarm. If the IAQ condition is still present after the IAQ Alarm Delay,
the alarm message is sent to the LCI.
Return Air IAQ
The VPU2 can read the status of an IAQ sensor placed in the return air duct. When the IAQ sensor indicates that con-
taminates are above a preset limit, the VPU2 energizes the fan. After a preset time delay, the economizer is enabled to
supply fresh air to the zones. All of the zones are made aware of the IAQ alarm condition. Any zone configured to par-
ticipate in return air IAQ modulates its damper open. Heating and cooling operate as normal.
Local Zone IAQ
The VPU2 can receive the status of local IAQ sensors connected to discrete inputs on each zone controller (VAVI).
When the local zone IAQ sensor indicates that contaminants are above a preset limit, the VPU2 energizes the fan.
After a preset time delay, the economizer is enabled to supply fresh air to the zones. Only the VPU2 and local zone
controller participate in local zone IAQ. Heating and cooling operate as normal.
Real Time Clock (RTC)
The RTC will be set or synchronized by the LCI each day at midnight. The controller will utilize the RTC in conjunction
with its local backup schedule during periods when the LCI is not available.
Local Backup Schedule
The LCI normally determines the operating mode. You can define a local backup schedule for situations when the LCI
is not available. When the controller detects that the LCI is not available (after 10 minutes without communications), it
resorts to the local backup schedule that has been configured. If the local backup schedule is disabled, the controller
defaults to the occupied mode.
The occupied and unoccupied times are used in determining the current operating mode of the controller when it is run-
ning the backup schedule. They are configured by the user. By default, both the unoccupied and occupied times are set
to zero, which disables the local backup schedule. This causes the controller to default to the occupied mode of opera-
tion when communications are lost to the LCI for 10 minutes or longer.
