User Manual

48/90
Building Technologies M-bus System CE1P5361en
HVAC Products 5 Engineering 08.02.2007
The SONOHEAT
®
heat meters with an M-bus module up to V1.06 produce a bus load
of 1.5. A SONOHEAT
®
heat meter with an M-bus module up to V1.06 corresponds to
1.5 devices: This means that a maximum of 5/1.5 = 3 SONOHEAT
®
heat meters with
an M-bus module up to V1.06 can be connected to an OZW111.
All other devices and SONOHEAT
®
heat meters with an M-bus module of V2.01 or
higher correspond to 1 bus load.
1 pulse adapter AEW21.2 with 2 active inputs represents 2 devices.
RVP97 district heating controllers and Siemeca™ AMR are not supported.
The OZW111 has the M-bus signal converter integrated. M-bus signal converters WZC-
P250 or WZC-P60 are not required. No M-bus repeater WZC-R250 may be connected.
For cables with a cross-sectional area of 0.8 mm
2
, following applies:
 The maximum permissible cable length between the 2 devices with the greatest
distance is 100 m
 The total cable length is limited to 500 m
5.4 M-bus
5.4.1 General
The M-bus conforms to EN 1434-3. It is continually developed by the M-bus User
Group and is now a widely used standard for data readout of heat meters, hot and cold
water meters, heat cost allocators, etc.
Detailed information about the M-bus can be found on the Internet under www.m-
bus.com/.
Compared to readout with the help of pulses, the M-bus offers the following benefits:
 The data read out correspond to the display on the meter. Pulses will not be lost
 The pulse source (initial reading, pulse valency, etc.) need not be programmed
 More information is provided
Compared to other bus systems (LON, EIB, CAN, etc.), the M-bus offers the following
benefits:
 Very reliable data transmission
 High immunity level
 Moderate connection costs
 Low cabling costs
 Long distances without requiring repeaters
 Large number of devices without requiring repeaters
 Any choice of topology
 Favorably-priced integration of battery-powered devices
 Adequate data transmission rate
Owing to the support of a large number of standard data, the M-bus central units can
read the majority of M-bus devices with no need for making specific adjustments. How-
ever, with M-bus devices using supplier-specific data, or with devices demanding sup-
plier-specific processes to read data, adjustments for the support may have to be
made.
5.4.2 Fundamentals
 Single master-slave principle: Within an M-bus system, only 1 M-bus master is
permitted (e.g. OZW10 with WZC-P250)
 Data transmission is always triggered by the M-bus master. The connected M-bus
devices (slaves) cannot answer on their own
 Transmission mode is asynchronous, half-duplex
Note
M-bus cable lengths
Features
Bus principle