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.

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.

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.

IMPORTANT

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.

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 nviManCool respectively.

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 nviFanSpeedCmd

IMPORTANT

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 variable nviReheatRelay.

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.

EN2B-0285GE51 R0909

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Honeywell W7752D Zone Control Options, Output Configuration Options, Input Configuration Options, Network Variable Binding
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W7752D specifications

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