Controls News 13
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Products:
Innovation in using BACnet
Extensions of BACnet standards are not always
compatible
Time poses a further risk. The BACnet standard is not
static. For 20 years it has been continuously devel-
oped by the members of the BACnet Interest Groups.
These include institutions such as universities, end
clients with large installations, system integrators
and of course device manufacturers, who have the
greatest influence. Continuous innovations and re-
quirements take the form of so-called Addenda to
the BACnet standard. On a regular basis – e.g. every
four years – these addenda are included in the BAC-
net Standard and released as a new version of BAC-
net Norm. But not all versions are always 100% back-
wards compatible.
For example, the format of the time-stamp of his-
torical data for devices dating from 2001 to 2004
was changed. Consequently, SCADA systems based
on the 2001 standard could no longer process data
correctly from 2004 devices. As a result, the end
clients either had to work with two SCADA systems
or upgrade all the 2001 devices in the entire BACnet
BA system with the 2004 version. It was expensive
and frustrating. In 2010, the 2008 standard became
the only valid basis for new BACnet tests. Unfortu-
nately it is not always backwards compatible with
everything either. For example, after revision 1.10,
ANSIX3.4 character encoding was replaced with UTF-
8.
But there are no other possibilities of distinction
in the text itself. This can have consequences for ex-
isting SCADA systems that process text according to
ANSI X3.4 following extension of a device with UTF-
8
coded text. For text without particular encoding
there is no problem, but there is the threat of unfore-
seen consequences if the text has been written in
the original language with encoding. These are just a
few examples of the many possible problems facing
system integrators and end clients, even with
BACnet.
What can be done?
Clear specifications during the planning phase are
key, and adherence to them must be monitored.
Planners who are unfamiliar with BACnet often have
their own guidelines for BACnet configurations. A
good alternative to this is to make the AMEV recom-
mendations for BACnet binding planning specifica-
tions at the tender stage. These recommendations
are really practical and have been proven in many
facilities. They define the minimum features that a
BACnet device must have in order to be interoper-
able.
Installation of the BACnet monitor
The BACnet monitor is a tool for planners and op-
erators for checking compliance with specifications
for the configuration of BACnet devices. Individual
engineering specifications in the BACnet monitor
are then added in. The monitor cannot improve an
existing BACnet installation; but it can give a trans-
parent overview of all BACnet devices and anomalies.
This can have a direct effect on those involved and
ensure that the prescribed standards are met. In pre-
vious manual sample acceptance testing, it was left
to chance whether variant devices were detected or
not. The BACnet Monitor allows for fully automatic
live monitoring of the entire installation. To ensure
that operation is as secure as it was at the time of
acceptance, the BACnet monitor checks each con-
nected BACnet device for compliance with the rules
agreed initially. Anomalies are recorded and reported
to the operator.
Principle function of the BACnet
monitor: Individual planning
specifications as assessment
criteria for testing all BACnet
devices in the BA system.
Planning
conventions
Test
Monitor interoperable functions:
Input
Planning conventions
Operation
Testing BACnet devices
for compliances with regulations
Output
report and protocol
The publishers of planning
guidelines for public buildings
have determined methods for
interoperable BACnet commu-
nication in order to ensure fair
competition.
