This page last changed on Aug 09, 2010 by jknottjames.

Hi,

It's been a while since I last posted, as we've been right in the thick of the build... but I've finally got to the stage where I'm putting in the wiring / electrics / lights etc, and the one thing that has become obvious, is that the money I was hoping to have available for light / home automation is just not there.

Instead what I'm going to do is install knx cable to each light switch in the house that I want to automate (including dimming), then once I've got the money, connect it to the switch and buy the appropriate modules...

Overall I'm going to have about 12 different light sets that will need automation, so I will just run the KNX cable to each switch, then bed it in the wall behind the plastering until a little further down the line when I have the money to install it.

My questions are:

1. how is this KNX cable attached to the light switch? Do I use the normal light switches, or do I need to buy custom switches for this?
2. my electrician is wiring the lights / electrics as it should be wired in the UK, with a permanent live feed to each light that is controlled by the switch. Seeing as though this has already been done, I can't change it. So if this isn't right, then I assume there's no point me running out the knx cable!?
3. can I run this KNX cable out to other points? For example, lay out some spare KNX cable for integrated music, movies, tv etc?
4. For my internal network I'm running out CAT 6 cables (about 18 network points so far). This has all now been installed, but I'm assuming I can't use this instead of using the KNX cable?
5. These KNX cables are being run direct to each light switch from a central hub located under the stairs in the basement. In the same room is the fuse board / electrics etc. It will be in this room that the modules will eventually be housed. So how does this part of the install work?

I'm sorry these are such basic questions. When you're doing a house build there are so many things going through your head, it's a surprise you're able to sleep at all!

Anyway, any help / guidance would be appreciated.

Kind regards,

James

Also, I'm installing underfloor heating on both floors of the build and wondered what I would need to do to integrate automation of heating? Each room will have a thermostatic controller for the underfloor heating, so for each thermostat location, would I need to run out KNX cable to it? Bear in mind we're using 3 core wire, which means I'm assuming one of the wires can be used for automation?

In our bedrooms however, we will have radiators, so what would be the best way of automating the control of these?

Again, thanks for your time and patience. At this point of the build, it feels as though my heads going to burst!

Posted by jknottjames at Aug 09, 2010 10:33

Just a correction from my first post, what I should have said instead of "permanent live feed to each light that is controlled by the switch", is "permanent live to each switch and a switch live to each light fitting..."

Posted by jknottjames at Aug 09, 2010 10:57

Hello James,

I'm not sure to understand everything here, but I'll try to provide a few answers.

First thing, a KNX installation has a different cabling comparing to a classic installation. Mainly, you will have a control network (a set of KNX devices, linked together with an appropriate medium) and a power network. You can illustrate this with the following picture : http://cibdi.com/images/schema-tebis2-hager.jpg. The "control network" on the left of the picture is composed of sensors (switches, presence detectors, weather stations...), providing informations to the actuators (usually located in the electrical panel). These actuators then controls the end device, by switching, dimming (...) the appropriate power source (aka. the power network on the right of the picture).

This mean that all your lights should be individually cabled directly to your electrical panel (but there are workarounds). Also, you won't have any classical switch, they should be replaced with KNX equivalent devices (push-buttons for example).

For your underfloor heating, I guess it's an electrical one ? If so, you may use a "pilot wire" module, with KNX logical thermostats

Mathieu

Posted by mgallissot at Aug 10, 2010 13:13

Hi Mathieu,

Thanks for your reply: my initial question here is really relating to the cable I've got to set out to serve our home automation network. I just need to understand the initial cable infra structure ...

At the moment each light is going back to a light switch (up to 6 lights being controlled from one switch). Then I'm running KNX cable (twisted pair) to each light switch. I'm just hoping this is the correct way of installing the cable?

Then I want to know if I just lay out KNX cable to places in the house where I can control other devices (such as music/videos/computers etc)

As you can tell, I'm a newbie to this, but I'm wanting to make sure I run the cables to the right place!

Kind regards,

James

Posted by jknottjames at Aug 10, 2010 15:37

Hi James,

"each light is going back to a light switch" => each light should go to a KNX actuator (relay or dimmer). Actuators are usually located in the electrical panel, but they can be placed closer to the lights.

"Then I'm running KNX cable (twisted pair) to each light switch" => correct, but the light switch should be a KNX device, not a normal light switch.

Wired KNX is a bus, you won't need a star topology. Thus, it is a dedicated network, you won't be able to use it for anything else that KNX communication.

You should have a look to the knx website for documentation. There are also a number of manufacturers who provides excellent documentation for starters.

Posted by mgallissot at Aug 11, 2010 07:53

Hi Mathieu,

Thanks for your reply. I have added these questions:

"each light is going back to a light switch" => each light should go to a KNX actuator (relay or dimmer). Actuators are usually located in the electrical panel, but they can be placed closer to the lights."

---Each light (the bulb that swings from the ceiling) goes to a light switch which is positioned in the room where the light is. Each light switch controls about 2 - 6 lights (depending on the room). Then I'm running KNX cable to each light switch from a central place... I will later put in a KNX switch device to operate it.

"Then I'm running KNX cable (twisted pair) to each light switch" => correct, but the light switch should be a KNX device, not a normal light switch."

---Understood

"Wired KNX is a bus, you won't need a star topology. Thus, it is a dedicated network, you won't be able to use it for anything else that KNX communication."

---Are you saying that I can loop the KNX cable between each light switch without returning back to the central location until the last device? As I said, at the moment I'm running an individual line of KNX cable for each back to the central hub...

"You should have a look to the knx website for documentation. There are also a number of manufacturers who provides excellent documentation for starters."

---I have tried to find these sort of documentation but failed to come across any? Any chance you can direct me to some links which displays information / documentation that I will be able to understand?

Thanks again Mathieu,

Kind regards,

James

Posted by jknottjames at Aug 11, 2010 08:16
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