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Sequence of operation
Unoccupied mode
When the controller is in the unoccupied mode, the controller attempts to
maintain the space temperature between the configured unoccupied heating and
cooling setpoints, based on the measured space temperature. Similar to other
configuration properties of the controller, the locally stored unoccupied
setpoints can be modified using Rover™ service tool.
Constant volume space temperature control
In unoccupied mode the supply fan is off whenever the space temperature is
between the unoccupied heating and cooling setpoints. If the space temperature
rises above the unoccupied cooling setpoint the Tracer™ AH.540 turns on the
supply fan and provides cooling at the discharge air temperature setpoint low
limit.
If the space temperature drops below the unoccupied heating setpoint the
controller turns on the supply fan and provides heating at the discharge air
temperature setpoint high limit. See Table 40 Discharge air setpoint limits for
constant volume space temperature control in the Configuration section of this
manual.
Constant volume discharge air or variable air volume control
For unoccupied heating or cooling operation the controller must have a space
temperature input either hardwired or communicated from Tracer Summit™.
In unoccupied mode the supply fan is off whenever the space temperature is
between the unoccupied heating and cooling setpoints. If the space temperature
rises above the unoccupied cooling setpoint the Tracer AH.540 turns on the
supply fan and provides cooling at the discharge air cooling setpoint.
If the space temperature drops below the unoccupied heating setpoint the
controller turns on the supply fan and provides heating at the discharge air
heating setpoint. See Table 41 Discharge air temperature control setpoints and
setpoint limits in the Configuration section of this manual.
If configured for variable air volume control, supply fan will control duct static
pressure at the duct static pressure setpoint.
Note that primary heating or cooling capacity is defined by unit type and
whether heating or cooling is enabled or disabled. For example, if the
economizer is enabled and possible, it will be the primary cooling capacity.
If hydronic heating is possible, it will be the primary heating capacity.
Occupied standby mode
In the occupied standby mode, the controller uses the occupied standby cooling
and heating setpoints. Because the occupied standby setpoints typically cover a
wider range than the occupied setpoints, the Tracer AH.540 controller reduces
the demand for heating and cooling the space. Also, the outdoor air economizer
damper uses the economizer standby minimum position to reduce the heating
and cooling demands.
Occupied standby is a mode in which the controller has received an occupied
™
request from Tracer Summit
, but has also received a local unoccupied binary
input IN 9 signal. For example, an unoccupied conference room (as sensed by a
local occupancy sensor) in an occupied building (as commanded by Tracer
Summit) is in occupied standby mode. When the conference room becomes
occupied with people, the local occupancy sensor changes the controller mode
to occupied.
The controller can be placed into the occupied standby mode when a
communicated occupancy request is combined with the local (hardwired)
occupancy binary input signal. When the communicated occupancy request
is unoccupied, the occupancy binary input (if present) does not affect the
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CNT-SVX05A-EN
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