iWorx® MPU2
505-009, Effective: June 30, 2015
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© 2015 Taco Electronic Solutions, Inc.
When an indoor air quality condition is sensed by the controller, the economizer is opened to 100%. If the mixed air
temperature drops too low, the economizer modulates in an attempt to maintain the IAQ MAT setpoint while still allow-
ing 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 controller can read the status of an IAQ sensor placed in the return air duct. When the IAQ sensor indicates that
contaminants are above a preset limit, the MPU2 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 config-
ured to participate in return air IAQ modulates its damper open. Heating and cooling operate as normal.
Local Zone IAQ
The MPU2 can receive the status of local IAQ sensors connected to discrete inputs of each zone controller. When the
local zone IAQ sensor indicates that contaminants are above a preset limit, the MPU2 energizes the fan. After a preset
time delay, the economizer is enabled to supply fresh air to the zones. Only the MPU2 and local zone controller partici-
pates in local zone IAQ. Heating and cooling operate as normal.
Smoke Detection
A smoke detector input is provided. If the smoke detector indicates smoke is present, then all of the stages and the fan
turn off. Once the situation has been corrected, reset the controller to clear this condition.
Mixed Air Low Limit Detection
An input is provided for a mixed air low limit detection device. If a low limit condition is detected, all of the stages and
the fan turns off. The controller returns to normal operation after a reset. After the controller switches from unoccupied
mode to occupied mode, there is a ten minute delay before it reports Mixed air Low Limit alarms. If heating and cooling
are configured as modulated or floating point, the heating valves open to 100%.
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 controller application is not shutdown due to a filter alarm.
Real Time Clock (RTC)
The RTC will be set or synced 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.
