Sequence Of Operation - Trane Tracer AH.540 Installation Owner Diagnostics

Sequence of operation

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The Tracer AH.540 is a configurable controller. All of the controller's sequences
of operation are predefined with no need for programming the controller.
Configurable parameters are provided to allow user adjustments to the
controller's operation. For example, the minimum occupied outdoor air damper
position can be changed.
All configuration parameters are set to defaults predetermined through
extensive air handling unit testing in several different operating conditions.
The factory default settings are also based on the air handling unit
configuration and order information.
The Tracer AH.540 controller is configurable to operate in one of three air
handling modes of operation:
• Constant volume space temperature control
• Constant volume discharge air temperature control
• Variable air volume (VAV) control
The Tracer AH.540 controller requires both a space temperature and discharge
air temperature sensor to be present for constant volume space
temperature control operation (also called cascade control). In this control
mode, the controller compares the space temperature to the space heat/cool
setpoint to generate a discharge air temperature setpoint. The controller
modulates its heating or cooling outputs to control the discharge air
temperature to the discharge air temperature setpoint. This calculated
discharge air temperature setpoint is the desired discharge air temperature
(supply air temperature) that the unit must deliver to maintain space
temperature at the space heating or cooling setpoint.
The space temperature can be hardwired to analog input 1 (IN 1) on the
termination board (10kΩ thermistor only) or can be communicated to the
controller via Comm5. Similarly, a setpoint can be provided with either a
hardwired setpoint adjustment to analog input 2 (IN 2) on the controller, with a
communicated value, or by using the stored default setpoints in the controller.
The discharge air temperature must be a hardwired analog input (IN 4) to the
termination board (10kΩ thermistor only).
The Tracer AH.540 controller can be configured to operate in a constant
volume discharge air temperature control mode. The controller only
requires a discharge air sensor (10kΩ thermistor only) to operate in this mode.
Constant volume discharge air temperature control modulates the heating or
cooling outputs to maintain the discharge air temperature at the discharge air
temperature setpoint.
When the Tracer AH.540 controller is configured for variable air volume
(VAV) control, the controller maintains a discharge air temperature according
to the cool/heat discharge air setpoint, and duct static pressure at the duct static
pressure setpoint. The controller maintains duct static pressure by modulating
the fan analog output (AO 1) which is wired to the fan's variable frequency
drive.
The duct static pressure input can either be hardwired or communicated to
the controller via Comm5. If both a communicated value and a hardwired duct
static pressure value exists, the communicated value has precedence. Similarly,
the duct static pressure setpoint can either be configured (default) or
communicated. If a communicated value is present, the communicated value
has precedence.
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