Guidelines for KNX group addresses
In order to program KNX efficiently and to make your KNX projects run smoothly from start to finish, you need to think about how you are going to configure and document the KNX Group Addresses (GA for short) structures during the design and planning phases of your projects.
In this guide we will describe the different types of KNX group address structures and the best practices that can be used when designing, planning and configuring KNX system installations.
You will learn all about Group Addresses in lesson 1.8 of the Online KNX training part 1
Why the design of KNX Group Addresses is important
Some of the most common problems with KNX installations and ETS – programming arise from the following problems related to KNX group addresses:
- No clear overview or knowing where to find details in your KNX project.
- ETS programming is difficult and unclear if there is no clear KNX group address structure.
- If KNX group addresses are poorly structured, debugging is difficult.
- KNX group addresses that are poorly documented make visualization difficult.
- No descriptions or details available for KNX group addresses or group objects.
- Lack of flexibility in the design and configuration process that prevents the installer or integrator from easily adapting GAs (without making everything else a 'mess').
To avoid complications and to ensure trouble-free programming in ETS, KNX group addresses must be correctly structured, well documented and easy to read or understand (even for others).
Different types of group address structures
Sometimes you need to have different types of GA structures in the arsenal to suit the different types of KNX projects you are working on.
There is no 'magic' group address structure that is superior or works better than any other. The best GA structure is simply the one you know best and feel comfortable with.
However, there are still pros and cons to each of the different structures that we will describe below.
Function-based, building-based and device-based KNX group address structures
We can roughly divide the different GA structures into 3 main groups – based on functions, buildings and devices.
- Function based group address structure (promoted by the KNX association).
- Build-based group address structure (usually used in larger projects).
- Device based group address structure (more unknown, but still worth mentioning).
In addition, there are many different variations of these groups.
In fact, a device-based style can be seen as a variation of the function-based GA structure.
To simplify these group address principles, it's wise to think of them as just 2 different parts:
Main and middle structure – which sets the framework for how we build everything.
Group addresses that are the same for all types of structures – which we can call a GA set).
Separating the GA set makes it clearer how to build the main and middle structure.
An example for a Dimmer, where we use 5 GA. We call those 5 addresses together a Set.
(It is useful to name the GA in English, so that any other programmers or support from manufacturers will run more smoothly. Of course you are free in the name and language you use)
|Abbreviation (EN)||Role (EN)||Length||Abbreviation||Role|
|FB||Switch feedback||1bit||TM||Switching – Status feedback|
|VALFB||ValueFeedback||1bytes||WTM||Value – Status feedback|
Most common GA sets:
|1 SW||1 SW||0 TEMP||0 MOVE|
|2 FB||2 FB||1 SETP||1 STEP|
|3 DIM||2 FASHION||2 POSITION|
|4 VAL||3 OUTPUT||3 WIND|
|5 VAFB||4 FEEDBACK||4 RAIN|
|5 ENABLE||5 FB POSITION|
|6 DIAGNOSTICS||6 FB SLATS|
We can also see the differences between the main, middle and subgroup in this matrix.
|Style||Main group||middle group||Address|
|Feature based||Role||Sub-function||Channel name||*|
|Building based||Building part||Role||Channel name||**|
|Device based||Device type||Building part||Channel name||**|
* GO spread over different middle groups
** All GA in the same subgroup
So if you add your group address sets to these different structures, you have something similar to the example below.
NOTE: It is important to understand the difference between a group address structure and an group address SET .
If you do this separation, you can start by defining the group address set you prefer to use and then place it in your desired structure.
The 3 most commonly used group address structures:
What is the best group address structure to use for your KNX projects?
As we established at the beginning of this guide, there is no real 'best structure' that can be used.
The best group address structure to use is simply the one that you feel most comfortable using and that best suits your project.
And it's very likely that you'll want to mix different styles of GA textures into your own process, but there are a few things to consider first.
- Try to make the structure as clearly documented as possible. For example, the number of the subgroup should match the channel number to facilitate debugging.
- Give your group addresses a clear name. Just indexing and encoding the name is practical when you create the GA tree, but it takes a split second each time you have to work with the address when you need to remember it (or if you need to do a quick cross-reference) . You should also consider how difficult it is to rename a group address once the installer has moved channel 5 to channel 9. The more text you have to rewrite, the more likely you will forget the old text you used before. † This will eventually disrupt the readability of your KNX project (the ETS functions will really help a lot here).
- Think about the time you spend linking GAs in ETS. If you have to constantly look for GAs when attaching GAs to objects, then you should consider streamlining the structure (use functions in ETS or have the GA set in one middle group). Ideally, you should be able to open a device in Building Structure and display all objects for a given channel. And in another panel you open the group address tree and you can link all objects without having to scroll in the group address window.
One of the most efficient ways to use GAs is to have a combination of both device and function based structures – as this makes it easy to create the structure based on the devices you are going to put in the KNX project .
KNX Function Abbreviations
Some common abbreviations used for the functions are:
SW – Switching
DIM – Lighter / Darker
VAL or VDIM – Dimming value
FB – Feedback
VFB or VALFB – Value feedback
SA – Switch Actuator
DA – Dimming Actuator
BA – Blind Actuator
BI – Binary Input
HA – Heating Actuator
MAN – Collecting line
RAD – Radiator
FCA – Fan-coil actor
LK- Light Keyboard
SP – Sensor plate
RTR – Room Temperature Rollover ( Mode Change )
PRS – Presence object to activate heating
WDW – Window object to reset heating
Setpoint SETFB – Setpoint feedback
IND – Indication