Siemens RCC10U Technical Instructions

RCC10U

Technical Instructions

Document No. 155-712

September 27, 2007

Room Temperature Controller
for Two-pipe Fan Coil Units

Siemens Industry, Inc.

Description

Room temperature controller for two-pipe fan coil units.

Features

• Output for on/off valve actuator.

• Output for three-speed fan.

• Dual setpoint temperature scale.

• Control depending on the room or return air temperature.

• Automatic Heating/Cooling changeover.

• Operating modes: Normal, Energy Saving, Freeze Protection and Off.

• Operating mode changeover input for remote control.

• Selectable control parameters.

• Operating voltage 120 Vac.

Application

Typical use:

• Controlling room temperature in individual rooms that are heated or cooled with two­pipe fan coil units.

• Opening or closing a valve

• Switching a three-speed fan.

Suitable for use in systems with:

• Automatic Heating/Cooling changeover.

• Heating only/Cooling only or Heating and Cooling applications.

Product Number

RCC10U With input for return air temperature sensor

Technical Instructions RCC10U Room Temperature Controller
Document Number 155-712 for Two-pipe Fan Coil Units
September 27, 2007

Page 2 Siemens Industry, Inc.

Accessories

ARG70 Adapter plate, for 2-inch × 4-inch or 4-inch × 4-inch electrical wall boxes
QAH11.1 Changeover/remote sensor
141-570 Lockable Thermostat Guard

Ordering

The QAH11.1 temperature sensor (which can be used as a return air temperature or
changeover sensor), and valves must be ordered separately. An ARG70 Wall Box
Adapter (used to mask the drywall when mounting the controller to a 2-inch × 4-inch or
4-inch × 4-inch electrical wall box) must also be ordered separately.

Table 1. Equipment Combinations.

Product Number

Description

Technical Instructions

QAH11.1

Temperature Sensor

155-329P25

599 Series

Two-way and Three-way
Zone Valves

155-320P25

SF Series

Zone Valve Actuator

155-321P25

Warning/Caution Notations

WARNING:

Personal injury, or loss of life may occur if you do not follow a
procedure as specified.

CAUTION:

Equipment damage, or loss of data may occur if you do not
follow a procedure as specified.

Functions

The controller measures the room temperature with its integrated sensor or external
return air temperature sensor (QAH11.1)—if used—and maintains the setpoint by
delivering control commands to the two-position (on/off) valve.

The switching differential is adjustable; it can be 2°F (1°C) or 7°F (4°C) in Heating
mode, or 1°F (0.5°C) or 3.5°F (2°C) in Cooling mode.

Fan Operation

The fan is switched to the selected speed via control output 11, 10 or 9 (Low, Medium
or High).

When the Temperature-dependent fan control function is activated (can be selected
with DIP Switch No. 1), the fan and valve are switched ON or OFF depending on the
temperature.

It is switched OFF by:

• Leaving the Heating or Cooling sequence, if the function Temperature-dependent
fan control is activated.

• Manually changing to Standby , if room conditions do not call for Freeze Protection
mode.

• Activating an external operating mode changeover switch, if installation conditions
do not call for Energy Saving or Freeze Protection mode.

• Turning the controller’s power supply OFF.

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.

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.