EXCEL 10 FCU CONTROLLER LNS PLUG-INS USER GUIDE
APPENDIX B: CONFIGURING FOR MASTER/SLAVE OPERATION
More than one Excel 10 FCU Controller may be used to
control the temperature of a room. In this situation one
controller must be identified as the master unit which will
perform the temperature control algorithm. The other FCU
Controllers in the room are designated as slave units, and
their control algorithms are disabled. The slave units receive
heating, cooling, and fan output information from the master
controller via network variables sent across the LonWorks
network. There can be a maximum of one wall module active
in the room, and it must be wired directly to the master
controller. If a slave controller has a wall module connected to
it, the wall module will be ignored.
Configuration of the master controller is the same as for any
controller operating alone in a room. Configuration of the
slave controllers must follow the rules described in this
section. The following sections correspond to the screens in
the LNS tool used for configuring Excel 10 FCU Controllers.
An additional section discusses binding of network variables
to support master/slave configurations.
Output Configuration Options
Slave devices must have their outputs configured identically
with the master controller. The same system type and
actuator types must be used. Valve run-times, cycle times,
and PWM zero and full position configuration options must be
the same as well. If the master controller has a reheat output,
the slave units must have one; and both must be configured
the same. Fan control in the slave units is via network
command from the master unit.
The fan minimum on-time must be configured to zero
in the slave controllers so that the fans in both
master and slave units switch ON at the same time.
Input Configuration Options
Slave controllers may have wall modules connected to them,
but they must be deactivated while the controllers are
operating as slave units. They must be configured for no
temperature sensor and no fan speed switch. The digital
input may be used on the slave units for window open/closed
or air flow (fan fail) detection and must be configured as such.
In the case of window sensing, the window status network
variable must be mapped to the master controller as the slave
controller does not execute the control algorithm.
Equipment Control Options
Valve action and fan interlock settings must be the same as
for the master controller. Output staging hysteresis, minimum
stage OFF times, and reheat switching and hysteresis should
be the same as in the master controller.
If a fan is used in the slave units, all fan control settings must
be the same as in the master controller.
All heating and cooling stage switching levels should be
identical to those of the master controller.
Zone Control Options
All zone temperature control options including PID settings
and miscellaneous settings are used only by the master
controller and are ignored in the slave units.
Network Variable Binding
In a master/slave configuration, the control algorithm is
executed in the master controller only. Heating and cooling
output as calculated by the control algorithm is then sent via
the network to the slave controllers. The master controller
output variables nvoHeatOutput and nvoCoolOutput must be
bound to the slave input variables nviManHeat and
For a master/slave system using heat/cool changeover, the
master controller output variable must be bound to the slave
controllers' input NV nviApplicMode unless a changeover
contact is connected to the slave devices. The binding of
these two NVs is also required in applications where heat/cool
energy is not always available.
The T7780 wall module must be connected to the master
controller. The master controller output variable nvoFanSpeed
must be bound to the slave controllers' input variable
The OFF position of the fan speed switch on the wall
module turns OFF heating and cooling control
functions as well as the fan, so the network variable
binding described above for fan speed must still be
performed as described.
For applications with reheat, the master controller output
variable nvoReheat must be bound to the slaves' input