3/11
Siemens
Temperature Controller RRV851
CE1N2725en
Building Technologies
27.08.2007
Mechanical design
The RRV851 is a temperature controller providing connection of power supply,
inputs/outputs and QAX850 master room unit.
27
25
Z
01
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
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:
Connection terminals
Bus interface
(HB+ HB–)
RS-485
(TX+, TX–)
Digital inputs
(D1, D2)
Temperature sensor
input (B1, M)
