ISBN 978-1-5272-2239-7
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Author:
Manfred Meier, aka “EIBMeier”
Golden rules for KNX
If you become accustomed to working with these simple basic rules, you will probably save many hours of tedious troubleshooting in your future KNX projects.
These rules alone should save you so much time and money that this E-book will have paid for itself in any case!
I recommend that you keep these rules close by whenever you work on a project and always follow them. Trouble-free and functioning KNX systems will be your reward!
These rules are not available in any other book. These rules are, so to speak, my very own
“golden rules” which I’ve gathered during my numerous projects and many years of KNX experience.
Rule # 1
A sensor can send one sub-group (function) per rocker switch/button (special cases possible). An actuator can monitor (execute) several subgroups per channel.
Note:
Actuator = executing/receiving KNX device (e.g. actuator)
Sensor = commanding/sensing/sending KNX device (e.g. touch sensor/temperature sensor, timer, etc.)
Example:
You have a single push button with two rockers (upper and lower) that turns a light on and off.
Now a second function (e.g. another light on and off) should be added at this location. You can program this second function (sub-group) “on top” of the existing single push button in ETS, but which of the sub-groups should the single push button now execute? It automatically takes the sub-group that has been linked first and sets it to “send”.
In this way it turns the first light on and off perfectly. However, the desired secondary function is not executed.
Every function that must be manually triggered (not automatically) requires a free rocker on a push button or a different sensor (e.g. conventional push-button with KNX binary interface).
Example:
In an existing KNX system, a new function (e.g. to switch off all office lights) must be implemented. You now only have 2 options.
1. Somewhere in the KNX system, there is a free rocker with a push button and the customer is satisfied with the position (location) for the desired function.
Solution:
Create the desired function and link it with this free rocker/button accordingly.
2. There is no rocker available or there is a free rocker, but the function cannot be run from this location.
Solution:
Create a free rocker! You have KNX! Clarify the desired location for operation (e.g.
where there is already a KNX sensor or at least the KNX cable present). Or, for example, remove an existing single push button and install a 2-fold touch sensor. In ETS, the previous function of the “old” single push button is programmed for one of the two rockers of the new 2-fold touch sensor.
Rule # 3
Each function (whether triggered manually or automatically) requires its own sub-group!
Explanation:
A subgroup (group address) is a group of numbers (for example, 1/2/1) that is created in ETS and needed to connect (link) the various group objects (functions).
A group object is the “connection point” of a KNX function, which is provided in ETS by the KNX device. You can also designate group objects as “connection terminals” for the desired KNX function.
“You may not believe me right now, but with these 3 rules you’ve already come very far with KNX!”
Rule # 4
Use only the original green KNX cable as a bus cable!
Explanation:
If you hear:
“I've also used an NYM-J as a bus cable” or
“A 0.6 J-Y(St)Y works as a KNX bus cable as well”
you should not be encouraged to try such suggestions. It is not only technically incorrect but may also lead to massive malfunctions and damage to the KNX system.
Always do the “pull test”!
KNX terminal “red/black” for sublines (red = plus black = minus)
KNX Terminal “white/yellow” for main lines (white = plus yellow = minus)
This refers to the KNX connection terminal! In the past, it was common for the KNX terminals not to do what they said they do (clamp/hold firm), and got loose easily. Always check!
In recent years however, this has improved considerably and today it’s rare that a KNX terminal doesn’t hold wires firmly.
Nevertheless: Loose contacts on the bus are unnecessary sources of errors. You should therefore make it a habit when inserting EVERY single wire to
> > > insert and pull back (= pull test)
If you don’t find a firm hold in any of the holes provided, throw the terminal away!
Loose contacts on the bus can lead to massive faults, even during commissioning (messages such as “errors in transmission” etc.).
Rule # 6 50 is the limit!
This means the number of KNX participants per line! KNX power supplies are available with 960mA, 640 mA, 320 mA and 160 mA.
To “calculate” the lines:
1 participant (actuator, sensor) needs approx. 10 mA (in old KNX technical books, the participants were still powered with only 5 mA!!)
Exception: control valve due to receiving the operating voltage directly from the bus. Please calculate with a factor of 2 (= 20 mA)!
Mathematically, a 640 mA KNX power supply can then “handle” 64 participants. However, you should plan the line at about 50 participants to be able to expand the line without any
problems!
Note:
You can also operate lines with more than 64 participants, but the manufacturers no longer guarantee that their products will function properly (when using a 640mA power supply, bus voltage gets too low potentially). At 256 participants, the absolute limit is reached, since the addressing of participants is only adjustable from 0 to 255.
Rule # 7
Each building has a building structure – always use it!
This refers to ETS. This allows (but unfortunately does not force) each project to be configured in the same structure as the physical building. This is done using a very simple method and greatly simplifies the work and the later overview. We will explain it in Chapter 3.
KNX is not PLC!
KNX is event-driven and not cyclically controlled!
When a specific event occurs, a telegram is sent to the bus that performs certain functions.
Afterwards, this event (telegram) is no longer present on the bus.
In a PLC, inputs are queried cyclically (in milliseconds) and then switched to the corresponding outputs via logic. The inputs are continuously queried (cyclically) and the appropriate reactions are triggered depending on the changes.
KNX events are usually only short pulses. A key is pressed (= event). The button sends a telegram to the bus, to which an actuator should respond.
Rule # 9
The function specifies the KNX device and its parameter settings and not the name of the sub- group!
If a button is to send an “all off” command, it must be specified correctly in the button parameters!
Rule # 10
Subgroups are the “virtual wires” – assign unique names!
Basically, KNX only requires the number combination of the subgroups to function (e.g. 1/2/21 for three-level subgroups). In plain language, this means that the KNX functions will also work even if you use the automatically suggested name “new sub-group”.
For clarity: you can also label the sub-groups as “Tom”, “Dick”, “Harry” or “Gobbledigook”. If you create the links properly, the KNX system will still work!
The correct names for the sub-groups are very important in a KNX project for you to keep an easy overview. You should therefore carefully consider what the sub-group does on the bus and give it a meaningful and easy to identify name.
Rule # 11
The number of KNX devices grows quickly – assign unique names!
Unique names for KNX devices are as important as those for the sub-groups. Imagine a project in which the term “touch sensor 1-fold” was assigned 20 times. Now imagine that in some rooms, several touch sensors are 1-fold and they have not been assigned to the correct rooms.
This means complete chaos in your project!
Rule # 12
First program the actuator, then the sensor/s
If the actuator has been programmed correctly, you can send the corresponding commands (logical 0, 1 or values) with ETS by right-clicking on the sub-group. If the command is executed correctly, the “actuator side” is OK.
Only when the actuator performs everything correctly while testing with ETS, should you consider which rocker/buttons should send this sub-group to which sensors and thereby run it.
Other recognized rules for KNX
The ETS computer should have an up-to-date Microsoft Windows operating system (OS).
ETS should be up-to-date (check in settings).
The device applications should be used in the latest version.
One building = one ETS project
Large projects must be created in several lines with couplers. Preferably, use main groups 0 to 13.
corresponding read flags (R flag) must be set correctly in the actuators and sensors.
Products without a KNX certification must not be used in KNX systems. This might break the system.
Group addresses must be well structured.
Group addresses must be labeled in a meaningful way.
The load on the bus must be kept as low as possible (caution with cyclical transmitters). Active feedback must be delayed after a bus reset.
Central functions must update the sensors (individual control buttons) – via the active feedback or central address monitoring.
Parameter settings must be fully completed. All functions must be tested.
Temperature regulators must be checked with a calibrated temperature meter and adjusted if necessary.
At the time of acceptance, all programming states must be fully uploaded.
There must not be any functions which are only switched by the commissioning PC.
Project data are customer data and must be transferred (if necessary sealed).
All project data must be transferred. Several data backups must be made.
The project version must be recognizable (specify date).
Special KNX devices, which are commissioned outside of ETS (e.g. certain panels, gateways...), must be created in the ETS project with the individual address (e.g. as a dummy or coupler) so that the origin of telegram recordings can be determined.
Incorrectly connected motor drives must have proper electrical connections. Reversing the direction via the parameters is not allowed.
Users should be able to change and save scenes they have created themselves.
Central functions should be used to illustrate a clear contrast to a conventional installation.
Couplers should normally be operated with a filter function.
Only one R-flag should be set per local group address.
The local function is the sending function (sending set, first group address).
User-friendliness should always be considered.
At least for actuators and binary inputs, notes must be entered in the description column.
Central functions must be clearly labeled and should be created in a separate middle group.
All changes in the programming should only be created when based on a specification. The project history must be used.
This PDF is an extract from our ebook “The Ultimate Guide to KNX Programming” which is available online at https://www.knxtutorial.com.
It is a simple and easy to understand tutorial on KNX and ETS 5 and gives you an introduction to the world of KNX technology. The course is designed to teach absolute beginners KNX and ETS and contains the following information:
From setting up a miniature system to systems with several areas, you will learn the correct cabling and procedures.
You will receive a detailed introduction to the ETS Tool Software version 5 - from licensing to installation, commissioning and an explanation of all essential functions.
The Ultimate Guide to KNX Programming guides you step-by-step through a project from A to Z laying out all the necessary steps in an easy to understand, practical way
• the necessary planning of a project
• the preparation of the actuators and sensors
• the detailed explanation of commissioning
• programming, final inspection and acceptance
If you are an electrician and are interested in an official KNX certification, this course is the ideal way to prepare for the optional certification courses.
KNX certification allows you to use the KNX partner logo in your own marketing activities (e.g.
stationery, cars). In addition, you will be listed as an official partner of the KNX Association (knx.org). These two advantages are a reason for many of our customers to get certified. The content of this ebook is adapted to the KNX basic course and the corresponding certification programme.
Furthermore, the products presented and used in the ebook are very often used in the
certification courses, so that you feel ‘at home’ with the products. This tutorial is therefore an ideal preparation for the certification seminar. However, certification is not a prerequisite for realising KNX projects. We, therefore, recommend everyone to gain practical experience in projects as quickly as possible.
Get started today and visit us at https://www.knxtutorial.com
