RCC10U Room Temperature Controller
Technical Instructions
for Two-pipe Fan Coil Units
Document Number 155-712
September 27, 2007
Siemens Industry, Inc.
Page 3
Heating/Cooling Mode
Output terminals 7 and 5 (neutral) command the control valve.
Output terminals 7 and 5 are open (0 Vac) when:
1. The measured room temperature is at half the switching differential below the
setpoint (Heating mode), and
2. The valve has been fully closed for more than one minute.
Output terminals 7 and 5 are closed (120 Vac) when:
1. The measured room temperature is at half the switching differential above the
setpoint (Heating mode), and
2. The valve has been fully open for more than one minute.
NOTE:
Output terminals 7 and 5 deliver a control command only for fail-safe open
(Normally Open) valve/actuator assemblies.
Fail-safe closed (Normally
Closed) valve/actuator assemblies cannot be used with the RCC10U
Controller.
Return Air Temperature
The RCC10U provides control based on either the measured room temperature or the
fan coil unit’s return air temperature.
Changeover is automatic if a QAH11.1 cable temperature sensor is connected to the
device. Place the sensor in the return air duct and terminate to the controller.
Order the QAH11.1 separately for return air sensing.
Automatic
Heating/Cooling
Changeover
CW = Chilled Water Cooling
mode
HW = Hot Water Heating
mode
M = Operating mode
SDC = Switching differential,
cooling
SDH = Switching differential,
heating
T = Room temperature
Tw = Water temperature
W = Room temperature
setpoint
Y = Signal voltage
The controller uses the water temperature measured by the changeover sensor
(QAH11.1) to switch from Heating to Cooling mode, or vice versa. When the water
temperature is above 82°F (28°C), the controller switches to Heating mode; below 61°F
(16°C) it switches to Cooling mode. If the water temperature is between the two
changeover points immediately after switching on, the controller will start in the Heating
mode. The water temperature is measured at one-minute intervals and the operational
status is updated.
Heating Mode
Cooling Mode
Automatic Changeover
Figure 1. Switch Action for Output Teminals 7 and 5.
Remote Changeover
Heating/Cooling An electric switch placed between input terminals 2 and 3 can
facilitate remote changeover. Terminals 2 and 4 must be bridged.
When the switch is closed, the Cooling mode is selected. When the
switch is open, the Heating mode is selected. Up to ten thermostats
can be connected in parallel.
Heating only
For heating only applications, input terminals 2 and 3 are open.
Cooling only
For cooling only applications, input terminals 2 and 3 must be
bridged with wire.
