20
CNT-SVX05A-EN
Zone sensor
The controller accepts the following zone sensor inputs:
• Space temperature measurement (10k
Ω
thermistor)
• Zone sensor setpoint adjustment (either internal or external on the zone
sensor module)
• Fan mode switch
• Timed override On request
• Timed override Cancel request
• Communication jack
• Service pin message request
Space temperature measurement
Trane zone sensors use a 10k
Ω
thermistor to measure the space temperature.
Typically, zone sensors are wall-mounted in the room and include a space
temperature thermistor. A valid space temperature input is required for the
controller to operate in constant volume space temperature control.
If both a hardwired and communicated space temperature value exist, the
controller ignores the hardwired space temperature input and uses the
communicated value.
Zone sensor setpoint adjustment
Zone sensors with an internal or external setpoint adjustment (1k
Ω
) provide
the Tracer
™
AH.540 controller with a local setpoint (50° to 85°F, 10° to 29.4°C).
An internal setpoint adjustment is concealed under the zone sensor’s cover.
To access the adjustable setpoint wheel, remove the zone sensor cover. An
external setpoint (when present) is accessible from the zone sensor’s front cover.
There is only one hardwired setpoint input (IN 2) associated with the Tracer
AH.540 controller. When the hardwired setpoint adjustment is used to
determine the setpoints, all unit setpoints are calculated based on the
hardwired setpoint value, the configured/default setpoints, and the active mode
of the controller.
Example:
Assume the controller is configured with the following default
setpoints:
Absolute setpoint Offset = setpoint Input - Mean setpoint
From the default setpoints in this example, the mean of the occupied cooling
and heating setpoints is 72°F [(74+70) / 2]. The absolute setpoint offset is the
difference between the setpoint input and the mean setpoint. For this example,
assume a setpoint input of 73°F, resulting in an absolute setpoint offset of one
degree (73 –72=1).
The hardwired setpoint is used with the controller's occupancy mode
(occupied, occupied standby, or unoccupied), the heating or cooling mode,
the temperature deadband values, and the heating and cooling setpoints
(high and low limits) to determine the controller's active setpoint.
Unoccupied cooling setpoint
85°F
Occupied standby cooling setpoint
76°F
Occupied cooling setpoint
74°F
Occupied heating setpoint
70°F
Occupied standby heating setpoint
66°F
Unoccupied heating setpoint
60°F
