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Parallel Fan Heat On Delay – For Parallel Fan terminals only, the controller has a configurable Parallel Fan Heat
On Delay to save energy. During the delay period (15 minute default), only the fan operates to recycle heat from
the ceiling plenum. If the heating requirement is not met by the end of the delay, the auxiliary heat is used.
Fan Heat Off Delay – For fan-powered terminals, the controller has a configurable Fan Off Delay. After the heating
coil is de-energized, the fan continues to run for the length of the delay to deliver to the zone any heat stored in
the coil. The default delay of 120 seconds is optimal for a ducted hot water coil. For ducted electric heat coils, the
nominal delay is approximately 45 seconds. For baseboard and non-ducted heat, the delay should be set at 0.
This feature applies to parallel fan terminals in both occupied and unoccupied mode and series fan terminals in
the unoccupied mode if the air source fan is off.
Demand control ventilation (DCV) and dehumidification using optional
sensors
The VAV Zone II's RH/CO2 input supports an optional CO2 sensor or Relative Humidity (RH) sensor. The sensor
can have a 5-volt maximum output. The range is configurable as either 0–5 or 1–5 volts (1–5 volt supports 4–20
mA sensors with a 250 ohm resistor). The controller's low and high sensor input configuration allows for a wide
range of sensors.
You can also connect ZS Sensors with CO
the controller determines DCV and dehumidification based on the highest sensor value and not the average. You
can adjust this in the i-Vu application or Field Assistant.
The controller can also support both DCV and dehumidification functions by using a system RH or CO
input connected to another controller.
NOTE If the connected sensor and/or system sensor value are to be used by the air source through Linkage, set
the appropriate control type to Enable. If you do not need local control at the zone, set DCV Max Vent Airflow or
Maximum RH Override Airflow to 0.
Demand Control Ventilation (DCV) – Requires CO2 sensor
The zone controller monitors the CO2 sensor and can override the temperature control to respond to increasing
CO2 levels when the zone is occupied. If the sensor's value remains below the DCV Start Ctrl Setpoint, the
Occupied Min Airflow setpoint provides the base ventilation rate as defined by ASHRAE. As the CO2 level exceeds
the DCV Start Ctrl Setpoint and the air source is in cooling or ventilation mode, the controller increases airflow to
the zone starting at the Occupied Min Airflow and then proportionally increases ventilation as the CO2 level
increases. If the sensor's value exceeds the DCV Max Ctrl Setpoint, the controller maintains the DCV Max Vent
Airflow until the zone's CO2 level decreases.
When the zone is unoccupied, the Unoccupied Min Airflow provides the base ventilation as required.
If the controller is configured for auxiliary heat, the controller will maintain the zone's temperature at a heating
setpoint that is temporarily increased to a value halfway between the heating and cooling setpoints when DCV is
active. This prevents an excessive drop in zone temperature caused by the additional ventilation. If auxiliary heat
is not available, the DCV Max Vent Airflow setpoint should be readjusted to prevent overcooling or set to 0 to
disable DCV at the zone.
VAV Zone II Controllers
Installation and Start-up Guide
and/or RH to the VAV Zone II's Rnet. If you have more than one sensor,
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51
Sequence of operation
sensor
2
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