Fan coil unit systems in commercial buildings control room
temperature through the control of heat and/or cold water
valves and fan speed. Electric reheat coils may also be used
in the system. The Excel 10 FCU Controller is located in the
FCU and is typically connected to an Excel 10 wall module
e.g. Excel 10 W7754
Excel 10 FCU Controllers provide room temperature control
for two- and four-pipe fan coil units with optional electric
heating coil. The basic control sequence is shown in Fig. 3.
As space temperature falls below the heating setpoint, the
heating output is increased. As space temperature
increases above the cooling setpoint, the cooling output is
modulated to 100%. Switching levels for staged
heating/cooling and fan speeds are configurable. The fan
may still be configured to run continuously during the zero
energy band in the "occupied" mode. Additional
configurable fan control features include fan minimum
ON/OFF times, run-up, and overrun-times.
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Fig. 2. Typical Fan Coil Unit control application
EXCEL 10 FCU CONTROLLER LNS PLUG-INS USER GUIDE
which incorporates a temperature sensor, setpoint and fan
speed controls, and a bypass or override button. Fig. 2 shows
a typical FCU ontrol application.
Excel 10 FCU Controllers use a PID control algorithm in
which each of the three parameters can be configured.
There are additional configurable boost parameters ("PID
Boost:" "Cooling" and "Heating") which specify a range
outside of which the heating or cooling outputs are turned
ON fully for faster response (in the case of thermal
actuators, this specifies the control hysteresis). The
controllers are delivered with factory defaults for each of the