Technical Instructions
RCC10U Room Temperature Controller
Document Number 155-712
for Two-pipe Fan Coil Units
September 27, 2007
Page 4
Siemens Industry, Inc.
Purging Function
The changeover sensor initiates the change from Heating to Cooling mode even if the
two-way valves are shut down for a long period of time. To ensure this function, the
valves are opened for one minute at two-hour intervals.
After power is reset to the controller, the heating and cooling valve will open for one
minute to flush pipes, for accurate remote changeover sensing. When this function is
completed, the changeover sensor will select the correct mode.
Setpoint Limit Stops
The room temperature setpoint can be limited in increments of 2°F (1°C) by using the
minimum and maximum setpoint limit stops. This prevents unauthorized setpoint
adjustment.
To set limit stops, remove the setpoint knob by pulling straight off the shaft. Reposition
gray tabs for high and low stops in the holes around the perimeter of knob as required.
See Figure 2.
Figure 2. Setpoint Limit Stops.
Operating Modes
The following operating modes are available:
Normal Operating Mode
Heating or Cooling mode with automatic changeover and with manually selected fan
speed: (Low),
(Medium),
(High). In Normal operation, the controller maintains
the adjusted setpoint.
Freeze Protection Mode
The Freeze Protection function is activated only when DIP Switch No. 4 is set to OFF.
Freeze Protection mode can be activated by:
•
Manually switching to Standby .
•
Activating the external operating mode changeover switch, if DIP Switch No. 2 is set
to OFF.
If the room temperature falls below 46°F (8°C), the controller will automatically switch to
Freeze Protection mode. In that case, the heating valve opens and the fan operates at
the selected speed. If the Standby mode is selected, the fan will operate at low speed.
The room temperature is maintained at a setpoint of 46°F (8°C) and the setpoint
adjusted by the user will be ignored.
If Freeze Protection operation is locked (DIP Switch No. 4 in position ON), Standby is
also locked, which means that the controller will switch to OFF instead of Standby.
