Trane LPC Install And Operation Instructions Download

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LPC-SVX01C-EN

Operation

sequence of
operation

Because the effective heat cool mode is
cool and the communicated value has
precedence over the local configuration
value, the discharge-air cooling setpoint is
50°F. The maximum and minimum
discharge-air cooling setpoint limits are
then applied to determine an effective
discharge-air temperature setpoint of
53°F, from Table O-SO-4.

In this example, if the effective heat cool
mode is Heat, the effective discharge air
temperature setpoint would be 100°F.

The discharge air temperature control
loop uses the effective discharge air
temperature setpoint, discharge air
temperature (from the wired sensor), and
the configured control gains to calculate
an output capacity for the end devices.

Heating/cooling mode control

The heating or cooling control mode of
the controller can be determined in
two ways:
1. Communicated request
2. Automatically by the controller

Communicated request

A building automation system or peer
controller may communicate the heating
or cooling mode to the controller using
network variable nviApplicMode. Heating
mode commands the controller to heat
only. Cooling mode commands the
controller to cool only. The Auto mode
allows the controller to automatically
change from heating to cooling or cooling
to heating.

Auto mode

A communicated request of Auto or the
controller default operation (Auto) can
place the unit into cooling mode. A zone
temperature input is required for
discharge air temperature control when
auto heat/cool changeover is desired.
When the controller automatically
determines the heating or cooling mode
using auto mode, the unit switches to the
desired mode based on the control
algorithm and the relationship between
zone temperature to the configured
daytime warm up start and stop
setpoints. See daytime warm up in
configuration section of this manual.

When the controller first powers up or
after a reset, it makes an initial determi-
nation if the discharge air temperature
control mode should be heating or

cooling. The discharge demand for a
cooling-only unit is always cooling. The
discharge demand for a heating only unit
is always heating. A unit that can heat or
cool initially starts in cooling mode.

Power-up sequence

This sequence applies to both space
temperature control and discharge
air temperature control. When 24 Vac
power is initially applied to the AH540/
541 controller, the following sequence
occurs:
1. Green Status LED turns On.
2. All binary outputs are controlled to

their de-energized state, and analog
outputs are set to the normally closed
output voltage.

3. The controller reads the inputs to

determine initial values.

4. Power-up control wait feature is

applied. The controller waits 300
seconds to allow ample time for the
communicated control data to arrive. If
after 300 seconds, the controller has
not received any communicated control
data, the unit assumes stand-alone
operation.

5. Normal operation begins assuming no

diagnostics have been generated.

Manual output test can be initiated at any
time in the power-up sequence or during
normal operation. Refer to the “Perform-
ing a manual output test”section.

Occupancy modes

The occupancy mode can be either
communicated to the controller or
hard-wired using the occupancy binary
input IN9+. The valid occupancy modes
for space temperature control are:
• Occupied
• Unoccupied
• Occupied standby
• Occupied bypass
The valid occupancy modes for discharge
air temperature control are:
• Occupied
• Unoccupied
• Occupied bypass

Occupied mode

The occupied mode is the normal
operating mode for occupied spaces or
daytime operation. The Tracer AH540/541
controller operates this sequence
according to the configured control mode.

Space temperature control: Occupied
mode

If configured for space temperature
control, the controller attempts to
maintain the space temperature at the
active occupied heating or cooling space
setpoint, based on the measured space
temperature, the discharge air
temperature, the active setpoint, and the
proportional/integral control algorithm.
Additional information related to
controller setpoints can be found in
“Space temperature setpoint
arbitration”section.

Discharge air temperature control:
Occupied mode

If configured for discharge air
temperature control, the controller
maintains the discharge air temperature
at the configured discharge air heating
or cooling setpoint. The default occupied
mode of the controller is cooling. In the
occupied mode, the controller
communicated application mode input
(nviApplicMode) and heat/cool mode
input (nviHeatCool) determine the
controller heating and cooling setpoint.

Unoccupied mode

The unoccupied mode is the normal
operating mode for unoccupied spaces
or nighttime operation. 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. The Tracer AH540/
541 controller operates according to the
configured control mode.