This page last changed on Sep 21, 2010 by johnortt.

Hi everyone. I have what I think is a regular complaint - I want Knx but I don't have the funds available to do it properly (at the moment).

The main things I am concerned with are lighting, heating and security.

I would like to wire my house traditionally (according to UK standards) but put all the wiring in the walls to allow me to upgrade piece by piece as time goes on.

Firstly can someone please clarify for me, do all knx devices need to be programmed. For instance if I buy a knx switch, can I just connect it to the power and the knx cable with all the light switches running off it and will it work or do I need to connect it to a hub and program it using the software?

There are some areas (I think) I have to do properly from the start, eg: Heating as I don't want to have to get a plumber in twice to replace a non-knx valve with its knx counterpart and the same goes for the room thermostats & controllers.

I was hoping some of you would be able to clarify a few issues I am having trouble with:

What is the best way to wire the house if I want to do a traditional setup but leave the ability to upgrade in the future?

What is 'best practice' in terms of KNX layout? Should the Heating controls be on a separate circuit to the lighting controls or should there be a single KNX circuit to each room containing all the controls (heating, thermostat, door and window sensors, light switches, smoke alarm etc)?

For the heating system we have installed water underfloor heating pipes. What is the simplest way to get this controlled by KNX?

If anyone can help I would greatly appreciate it.

one circuit of "green KNX cable" is already going to cost you an arm and a leg. If you are complaining about cost then yeah don't do MANY networks. It doesn't make sense either, everything can run on one green cable network.

Flexibility to upgrade and add things down the road isn't the best with KNX. you need to run cables to pretty much everything and that is sort of set in stone at construction time.

For the gear, you can shop and browse here :

I know these guys (based out of the UK actually) and they know their stuff. However the KNX stuff is OUTRAGEOUSLY expensive. But that is KNX and that is nothing new to you.

Good luck with your construction.

Posted by marcf at Sep 21, 2010 12:10

Why you need KNX? If the price and flexibility are factors, then KNX is just not for you. Try ZigBee, Xbee and other wireless technologies. They're much cheaper and provide the flexibility you need. However they are still relatively new technologies and there aren't many end-user devices right now.

Posted by mishoboss at Sep 21, 2010 16:20

Totally agree, also I will be at CEDIA later this week scouting the "rejects" pavillion, where all the gear is the new stuff.

This industry will look VERY different in 5 years and I know we will play a part in the software angle of it, right?

Posted by marcf at Sep 21, 2010 16:34

And I'm totally agree with you The software you're creating is innovative, multi-platform, multi-vendor and it's free... once there are features like creating rules and events and cameras support, I think OR will be the best HA software out there!

I would like to add that not only ZigBee, Xbee and so on wireless technologies will bring the HA to the mass market, but powerline too. Powerline is not dead. There are very interesting projects like DigitalStrom and others. There are new chips that integrate powerline phy with 6LoWPAN protocol stack (Watteco's WPC-IP, the upcomming Yitran IT900, Maxim IC's too). It's gonna be interesting next few years

Posted by mishoboss at Sep 21, 2010 16:52

Help out man, the project is growing fast with guys like you.

Posted by marcf at Sep 21, 2010 17:09

Thanks for the replies guys.

I had already found the knxshop and 250m of cable from them costs about £180 which is acceptable. I have yet to fully scope out the project but I am guessing (hoping) £500 would cover the initial cable, (as long as a single loop round each room is adequate).

The big problem for me is the consultation costs. I have had one quote of £4000 for schematics which is more than I paid my architect to design the house!

All I want is to spend less than £1000 on KNX wiring for the house and know I have everything I need to expand the system in the future. If I can also get heating control installed from the start for another £1000 or there about (and maybe security for another £1000) we are on to a winner.

The lights can (hopefully) be run off traditional switches for the time being.

Thats what I'd like anyway....reality might be quite different.

After many years working with computers I would have a wired network any day over a wireless one. I agree that wireless systems have their place, but I feel that when you have a fresh build and the opportunity to wire in a solution you should take it.

If I am way out on any of the above please feel free to point me in the right direction.



Posted by johnortt at Sep 21, 2010 17:14

Well, you're right, wired solutions are better than everything else. But they're also the most expensive ones.

If you have the knowledge and you're a DIY geek (like me), you could build yourself RS-485 modules with Arduinos and SN75176 for less than $25-$30 per module and run CAT-5 cable for a few cents per meter I did some prototypes of such modules and they work pretty well with OpenRemote, connected via USB to RS485 dongle and using Linux with ser2net deamon for TCP to Serial conversion (c'mon Marc, when will be the general Serial ready ). If you find this interesting, write me at mihail (at) m-design (dot) bg and I will help you with what I can.

Posted by mishoboss at Sep 21, 2010 17:58

If your cable needs are more modest, RS Components sell 100 metre reels:

KNX TP has a flexible topology, almost anything goes except loops. Most devices can support a fan-out of 3 so there is scope for reducing the total wiring length by daisy chaining. The disadvantage for domestic wiring is that the cable has a large cross section. Chasing one cable into a solid wall is messy. More than one, more messy. Wago have 8-way connectors: and holders: which can be used for junction boxes with a fan-out of 7.

The KNX cable specification is probably high enough that if you decided against using KNX you could probably run most other bus systems over it (the same cable is used by Wilo Geniax to control and power their miniature pumps).

Radiocrafts have a family of miniature KNX RF modules which might increase its popularity. Calao Systems have a neat USB key device that uses one of these modules:

The great thing about standards is that there are so many to choose from.

Posted by jconnett at Sep 21, 2010 18:33

John - think you might struggle to get your heating control in for £1000. We've been quoted £8.5k to provide for 13 "zones", including 13 thermostats, actuators to control the underfloor heating, IP Gateway, installation, commissioning and integration with our planned Opus Tech system. Though the cabling element was on arounf £750

I've just stumbled on OpenRemote and intend on using the Web Console, iPhone/iPad App for visualisations/control of the heating, and anything else we hook into the KNX in the future. The WebConsole + Controller will go on to the headless Media Centre PC linked to the Opus.

Unfortunately, Opus doesn't support 2-way comms with KNX, so we'll be able to control the Heating, but not see temps on the Opus displays.

I think OpenRemote looks an interesting proposition - it's also got me back in to building & tinkering with Java (something I've not done properly in about 5yrs!)

Posted by stuartb at Sep 21, 2010 23:39

I, too, think that £1000 would be a challenging target for an intelligent domestic heating control system. Note that in the UK you may be able to take advantage of reduced rate VAT (5%) on heating controls for low energy systems which might help.

If you are looking for an entry level KNX system then Siemens Synco Living ( might be worth a look. This is mostly based on KNX RF (with the potential for extension with KNX TP). It also appears to be a plug-and-pray system where basic configuration can be done without the need for programming by an expensive consultant using KNX ETS.

If your heating system is Viessmann they have Vitohome 300 ( which appears to be mainly badge-engineered Synco Living with some Viessmann specific parts (I have seen suggestions that the firmware may be different). Don't know if Vitohome 300 is available in the UK.

The above is based on reading manufacturers' brochures rather than direct experience so please don't commit large sums of money before doing your own research!

Posted by jconnett at Sep 22, 2010 08:29

Marc, I don't have strong knowledge in Java technologies, however I have some experience and I'm a fast learner. I've started modifying few weeks ago the Designer to add X, Y, Width and Height fields of the components, so they could be position on pixel level, not just dragged by the mouse. I would like to ask how could I commit the code I make?

Posted by mishoboss at Sep 22, 2010 09:50

You will need to create a patch for the changes you've made (i.e the diffs created by 'patch' command line tool).

Posted by juha at Sep 27, 2010 03:06
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