Trane LPC, Install And Operation Instructions

Page: 64 / 110

64 LPC-SVX01C-EN
Operation
sequence of
operation
When the controller is configured for a
supply fan and space temperature
control, the controller will not operate the
unit if the space temperature or dis-
charge air temperature sensors are
missing or have failed.
The space temperature control algorithm
uses two control loops: a space tempera-
ture loop and a discharge air tempera-
ture loop. The space temperature control
loop compares the active heat/cool space
setpoint and the space temperature and
calculates a discharge air temperature
setpoint. The calculated discharge air
temperature setpoint range is bound by
configurable heating (maximum) and
cooling (minimum) limits.
The discharge air temperature loop
compares the discharge air temperature
to the calculated discharge air tempera-
ture setpoint (calculated by the space
temperature loop), and calculates a heat
or cool capacity to respond to the
discharge air temperature setpoint.
The capacity calculation, as a result of the
discharge air temperature control loop, is
used to drive the air-handling unit
actuators to maintain space temperature
at the space temperature setpoint.
Control gains
Figure O-SO-1 illustrates the separate
control for the space temperature control
loop and discharge air temperature
control loop. The gain parameter values
that control the different loops have been
determined through extensive testing of
different types of heating or cooling
capacities and at operating conditions of
the air-handling unit.
Heating/cooling mode control
The heating or cooling mode of the
controller can be determined two ways:
1. Communicated request
2. Automatically by the controller
Figure O-SO-1. Space Temperature Control Block Diagram
Space temperature control loop
Space temperature
Space temperature setpoint
Space temperature control gains
Discharge air temp. setpoint limits
Discharge air temperature
Discharge air control gains
Discharge air temp. setpoint
Discharge air control loop
Calculate heat/cool capacity
Use capacity to drive actuators