Siemens RRV851 Quick Start Manual

725

2

Temperature controller
for ducted systems

Multifunctional controller used for central control of ducted HVAC systems in
connection with a QAX850 master room unit.
Standard model without zoning functions.

Use

RRV851

Applications

Comfort control of ducted HVAC systems via fan, heating and cooling output:

• Apartments

• Single-family houses

• Autonomous light commercial applications

The RRV851 controller is designed for central ducted HVAC systems that require easy
operation by the building occupant. The MMI to be connected to the controller is the
QAX850 master room unit. Fan, heating and / or cooling outputs control the
temperature in the building. The RRV851 controller can be configured for various types
of HVAC equipment. These include:

• Heating only ducted systems

• Cooling only ducted systems

• DX cooling and heating (1-speed fan on heating)

• DX cooling and heating (3-speed fan)

• Air-to-air heat pumps

• Water-to-air heat pumps

• 4-pipe FCU

• 2-pipe FCU

• 1- or 3-speed fans

CE1N2725en

27.08.2007

Building Technologies

HVAC Products

Functions

Application example:
4-pipe FCU system

The controller’s functionality is determined by the application selected with the DIP
switches, parameter settings and operating mode selection via the QAX850 master
room unit.

HB B1

Y1

Y2Y1Y3Q7Q8Q9

Y2

FCU

D1

D2

D2

N1

D1

Type summary

Note

SAF

B1

T

N2

B1 Optional remote temp. sensor N1 RRV851 controller
C1 Cooling coil N2 QAX850 master room unit
D1 Remote comfort mode input SAF Supply air fan
D2 Fault or emergency heat input Y1 Cooling control valve
FCU Fan coil unit Y2 Heating control valve
H1 Heating coil

C1

H1

Type reference Description Compatible with

RRV851

Temperature controller • QAX850 Master room unit

• QAA32 Room temperature sensor

• QAH11.1 Cable temperature sensor

The QAX850 is the master MMI for the RRV851 and must be ordered as a separate
item. Any additional remote temperature sensors must also be ordered separately.
Terminal covers are included in the RRV851 box.

2725A01

Not suitable for use with the Desigo RX range of wall-mounted units.

Product documentation

Document Document number

Data sheet N2725
Installation instructions G2725
Operating instructions, with QAX850 room unit B2725en01
Application manual A2725
Declaration of conformity T2725

Supporting
documentation

Document and unit type Document number

Data sheet QAX850 N2722
Mounting instructions QAX850 M2721

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Mechanical design

The RRV851 is a temperature controller providing connection of power supply,
inputs/outputs and QAX850 master room unit.

2725Z01

The unit consists of the following components:

• Base for DIN rail or screwed surface-mounting

• Cable strain reliefs

• IP30 covers (when mounted directly to the wall or FCU without DIN rail)

• PCB and built-in transformer

• PCB cover

• Input / output terminals

• RS-485 terminals

• MMI bus terminals

• LED for power supply indication

• Configuration DIP switches

Connection terminals

Bus interface
(HB+ HB–)

RS-485
(TX+, TX–)

Digital inputs
(D1, D2)

Temperature sensor
input (B1, M)

Low-voltage power supply (DC 12 V) and communication transfer is supplied via two
wires to the QAX850 from terminals HB+ and HB–. The LED on the QAX850 will flash if
a communication error exists between RRV851 and QAX850 for longer than 5 seconds.

The RS-485 connections are only suitable for downloading manufacturer specific
parameter sets. This is for factory use only.

Two digital inputs are provided. A potential-free contact closed across the D1 and
D_GND terminals will override to Comfort mode only when the mode selector is set to
Auto Timer mode. D2 can be configured for an emergency heating enable signal or an
external fault lockout signal. Either of these functions can be selected via the
configuration DIP switches.

When emergency heating is selected, a potential-free contact closed across the D2 and
D_GND terminals will disable the primary heating output and enable the emergency
heating output. The emergency heating output will only be activated when there is
demand for heating. Not available on applications A2, A3, A4, and A5.

When external fault (default) is selected, a potential-free contact closed across the D2
and D_GND terminals will deactivate all outputs and the standby icon on the QAX850
LCD will flash to indicate the fault. The fault will disappear after the contact is opened.

An NTC temperature sensor can be connected to the B1 and M terminals for the
following functions:

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Fan speed outputs

Heat/cool outputs

• Remote room temperature sensing: The QAX850 can be used as a master control
unit without using the built-in temperature sensor. A separate room sensor (QAA32)
can be mounted in a location more convenient for accurate temperature acquisition

• Return air temperature sensing: A temperature sensor (QAH11.1) can be mounted in
the return air path of the FCU if accurate temperature acquisition in the room is not
possible

• 2-pipe application heating/cooling changeover: For application A8 (2-pipe FCU) a
temperature sensor (QAH11.1/ARG86.3) is clamped to the water pipe in order to
activate heating/cooling mode changeover

The RRV851 controller can be configured for a 1- or 3-speed fan. Voltage-free (SPST)
relay outputs Q74, Q84 and Q94 can switch loads up to AC 250 V, 6 (4) A. Power is
supplied via terminal Q71. The low-speed terminal is used when a 1-speed fan is
configured. On fan startup, high-speed will be activated first for approximately
3 seconds and then resume the selected speed. In Auto Fan mode, the fan speeds will
be activated automatically depending on demand.
For further details on auto fan speed control, refer to the Application Manual.

• Output Y1: Cooling or compressor output

• Output Y2: Heating or reversing valve output

• Output Y3: Auxiliary output that can be configured for auxiliary heating, emergency

nd

heating, 2

step cooling or dual compressor
Output control is 2-position. 3-position modulating can be selected via parameter P17
for applications A1, A2 and A8 only.

Configuration

DIP switches

DIP switch settings

Initial application setup of the RRV851 controller to match the connected HVAC
equipment is made by the selection of DIP switch positions. DIP switches are located
on the top of the controller. An adhesive label is included in the RRV851 packaging box
for the final recording of the DIP switch positions. This can be placed on the DIP switch
block to avoid unauthorized changes. Further parameter settings can be made via the
QAX850 if required.

Function Selections 1 2 3 4 5 6 7

Y3
Auxiliary
output

Auxiliary heating 20 min delay
Auxiliary heating 10 min delay on off - - - - ­Emergency heating via D2 off on - - - - -

nd

stage cool or compressor on on - - - - -

2

off off

- - - - -

Single speed - - off - - - - Fan

speed

Applica­tion

Three speed - -

A1 – Heating only
A2 – Cooling only
A3 – Cool./(heat. 3 speed fan)
A4 – Cool./(heat. 1 speed fan)
A5 – Heat pump (comp + RV)
A6 – Heat pump (heat/cool)
A7 – 4-pipe FCU
A8 – 2-pipe FCU

- - -

- - - on off off off

- - - off on off off

- - - on on off off

- - - off off on off

- - - on off on off

- - - off on on off

- - - on on on off

on

- - - -

off off off off

Default (as delivered) positions are in bold text.

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