Lighting JB question

[eyeofthebeholder]

We are currently rewiring our house and will be commensing the lighting circuits in a few weeks.

I will be installing X10 home automation products on the lighting circuits to allow remote switching and control by the fire/burgular alarm system. You can install the X10 modules in the back boxes, but can only fit one in the backbox (unless you put 40+mm boxes in the wall). Tthis will be a problem if you have a 2+gang switch.

The alternative is to install these modules in JBs, but as everyone know, if you use them they have to be 'accessible' for inspection.

What I am thinking of doing is for each of the 3 lighting circuits (I live in a Town House), is to fit a box somewhere on each floor and install all the JBs with the X10 modules in this box.

So you will have the circuit coming in to the box from the CU looping through all the JBs. The JBs with then obviosuly have cables going to the switch(es) and light(s). This will result in some extra cabling etc, but it will mean that I will have complete control and accessibilty in the future if anything needs changing.

Looking at the Onsite guide there is a limit of 100m of cable. What am I actually measuring for the 100m? Is it the main circuit, switch cable length and lighting cable length?

Can any one see any other regulation issues with this setup? BTW, as I have already started the rewire, I am only bound by 16th Ed, as told to me by the LABC subcontractor.

Cheers

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[eyeofthebeholder]

Ok - I have made a to-scale diagram of what I am after.

I have changed the details from the desciption above. Instead of using JBs, I would like to use normal connection blocks instead which will be screwed to the board. The board will be boxed in, but accessable. I have only shown an example connection on one of the connection blocks.

Not knowing the 16ed Regs inside out, I am not sure if this design is in breach of them. I would appriciate any feedback on this..

Thanks

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[Dippy]

100m is for the total length of cable, including drops to switches.

 

[davelx]

With X10, the load current does not go via the switches - those are control circuits only. So you could argue that they ar enot inlcuded in the cable length,

 

[ban-all-sheds]

I will be installing X10 home automation products on the lighting circuits to allow remote switching and control by the fire/burgular alarm system.

I can't believe that they don't support something more modern than X10

The alternative is to install these modules in JBs, but as everyone know, if you use them they have to be 'accessible' for inspection.

Where are you going to get a junction box large enough to take an X10 module?

Looking at the Onsite guide there is a limit of 100m of cable. What am I actually measuring for the 100m? Is it the main circuit, switch cable length and lighting cable length?

The longest current path between CU and light via the switch(es).

 

[grahambishop]

You could look at the GET Smart lighting control system, far easier for wiring

http://www.getplc.co.uk/smart/wireless-lighting/default.asp

 

[plugwash]

I would like to use normal connection blocks instead which will be screwed to the board. The board will be boxed in, but accessable.

If you use terminal blocks they must be inside a suitable enclosure.

I would suggest getting a large box designed for fitting electrical stuff inside (e.g. http://www.tlc-direct.co.uk/Products/GWBX532.html ) and mounting your terminal blocks in there.

 

[eyeofthebeholder]

Hi Guys,

Thanks for your replies on this, even though I haven't replied to them - sorry for that! I have been investigating other ways of achieving what I want with different systems.

I have found that X10 suffers from a lot of noise. I purchased a few test units and found this noise on my electrics at home! I know I can get various filters etc, but I don't want to be left with this nagging in the back of my head everytime I plug something new into the power! I had found some X10 relay DIN mounted modules, which would have gotten over the enclosure issues.

Anyway, I am now looking a the CBUS system, which runs its comms over CAT5e instead.

The question I now have is that, as I am going to be switching ALL my lights through Home Comfort/CBUS relays, does that cause any issues with the regulations. For example do I now have to install completely separate emergency lighting or something, just in case the CBUS/Home Comfort goes belly up??

Over the weekend we went up to the National Self Build & Renovation Centre in Swindon and had a look at the house there with the home auto stuff. It didn't look as though they had anything else other than the digital light controls - but I dunno what was going on behind the scenes?

 

[eyeofthebeholder]

Looking at the Onsite guide there is a limit of 100m of cable. What am I actually measuring for the 100m? Is it the main circuit, switch cable length and lighting cable length?

The longest current path between CU and light via the switch(es).

I know this is a slightly pedantic question..

If you have a REALLY long switch cable length between several switches, do you calculate to the last switch and then back again? As this is the 'true path' of the current. For example:

CU - - 5m - - (LIGHT) - - 5m - - 2W Switch - - 5m - - Int Switch - - 5m - - Int Switch - - 5m - - 2W Switch.

The total cable length from the CU to the last Switch is: 25m.
But the current length is 45m

I assume you are going to say that at the end of day, if the testing passes the circuit for volt drop and impedance etc, all is OK??

Cheers

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