Made the mistake of going to IKEA

[ToughButterCup]

She fell in love with LEDs. So much so that I recon we might be able to install  a 12 volt circuit in the kitchen and bathroom.

I've searched for "12 volt circuits" here, and there aren't any. 

Do I really have to have a forest of sockets and transformers under the work surfaces or hidden above and behind cupboards? With all the warnings that @JSHarris has given us about cheap noisy  LED drivers full of RF interference, I'm wondering;  for 6 sets of LEDs in the kitchen 

• What's the lowest number of 12 volt circuits I can get away with for the kitchen ?
• Should we have a separate 12 volt circuit, or should we just install a/c sockets and plug each string of LEDs into them? 
• Very roughly, what's the maximum lead length for bell-wire size DC circuitry?
• Is it worth getting hard-core about this (for fun) and install our own transformer(s)

 

Anyone know of good online reading about LEDs in house builds? 

[Jeremy Harris]

I used small 12V switched mode power supplies, the type that have a built in fuse and that are in metal enclosures, and fitted them in the ceiling void.  The metal cased units don't seem to present the interference problems that some of the plastic cased units do, but there are some decent plastic cased units around, as others here have found them (I can't find the thread at the moment).

 

Bell wire is a no-no, as generally the current requirement may well exceed its rating and the voltage drop will be too high, even at a pretty low current.  There's nothing wrong with using ordinary T&E for SELV lighting, but best to mark the ends of the cables to indicate that they are being run at 12V.  1mm² T&E is good for 13A when run in a ceiling void with 100mm of insulation, 1.5mm² T&E is good for 16A in the same conditions, but the important thing with SELV is the voltage drop; it's far more critical than with LV.  You want no more than 5% voltage drop, which is 0.6V.  10m of 1mm² running at 10A would have a voltage drop of around 4.4V, which is way too much, the highest current you could run through 10m of 1mm² T&E and stay below 5% drop at 12V would be about 1.4A, and for 10m of 1.5mm² T&E the highest current would be about 1.7A.  If you use shorter lengths of cable, then the allowable current increases in direct proportion (so a 5m length doubles the above maximum current for an allowable voltage drop).

 

I fitted the power supplies pretty much centrally for each group, then ran radials out to most of the LEDs, to keep the voltage drop down.  Some radials have a couple of LEDs on, just because it made the wiring a bit easier.  All our ceiling LEDs are wired with 1mm² T&E like this, with a maximum cable run of around 2m or so.  Using T&E also means that the cable is mechanically tougher and easier to install.  To make it easier for anyone to work out what these cables are in future, every one has a white heatshrink label on the end, identifying the circuit and the voltage.  I also used red and black sleeves over the brown and blue cores, to make it clear which is the positive and which is the negative.

Edited May 21, 2017 by JSHarris
typo

[ToughButterCup]

Thanks very much J.

Ian

[Fallingditch]

"Anyone know of good online reading about LEDs in house builds? "

 

A few comments 

 

Try searching the site for "24V" - there's quite a lot of stuff under that heading.

 

When you say LED's, I assume you mean strips. Or you might mean panels. LED square or round panels are IMO an excellent alternative to compact fluorescent to provide general background lighting. In fact, we have done the whole house in LED panels (as have others). Very few negative comments. For rooms of size say 3m x 4m, I have found 2 x 18w panels provide ideal illumination.

 

Here is a picture of the kitchen diner with an array of 4 + 2 panels over the worktop:

 

You can also get LED sconces, btw.  (NB all from ebay - I cannot provide assurance as to the interference or longevity but at £9 each I will take that risk). We are also planning to fit strips to the plinths etc.

 

One more thing - I do think lighting plans are worth doing. Makes you think it all through - especially switch positions and how it will work in practice. Here's my amateur effort for that big kitchen/diner. The row of four is at the top of the plan. Two-way switches at each end of the room allow the array to be switched on/off independently:

 

It worked for the electrician 

 

I originally thought about putting is a 24V circuit to drive all panels and strips - but in the end I couldn't justify the expense. So all the individual panels come with their own transformers (which may come back and bite me) but the 4 strips are run from 2 x 24v transformers.

 

 

 

 

[Ferdinand]

My grandma and me went to IKEA and we bought:

 

12 Panel LEDs.

Two Lamb Shank Lunches.

And 2 HYBY hall lights http://www.ikea.com/gb/en/products/lighting/ceiling-lights/hyby-ceiling-lamp-white-art-90347389/

 

who's next?

Edited May 22, 2017 by Ferdinand

[jack]

There are few things in this world I dislike more than that game.

[Ferdinand]

It's a way of keeping the budget under control, so all self-builders hate it .