# Forum Home Renovation Lighting  240v wall switch for 12v LED system?

## martrix

Hi, quick possible stupid question but here goes anyway. Wanting to install some 12v LED strip lighting in some cabinets. So it matches in with the rest of the house, can I use a standard single pole 240v wall mounted switch? obviuosly on the 12v side and a new switch on the wall, not one thats already there. Estimate about 5A and 80W of juice, cheers for your help.

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## Ozcar

Is that 12V AC or DC that you will be switching? 
If AC, then for sure  no problem. 
If DC, it is a bit more tricky to answer, but my guess is it would be OK. 
The normal mains switches are rated for 10A 240VAC. Often you can see that without even pulling anything apart, with the rating being embossed on the rocker of the switch. Those are of course, maximum values. 
When used at a voltage lower than 240VAC, the switch can still handle at least 10A. In fact, at lower voltages it can probably handle more than 10A. Good luck with finding the actual current rating at 12VAC, but since you don't need to switch more than 10A you don't need to worry about that. 
The complication is that switches need to down-rated when used with DC (which is more prone to arcing than AC). Here are some actual ratings for a switch I happen to have here: 10A at 250VAC, but only 250mA (¼ amp) at 250VDC, or 500mA at 125VDC. I don't have any other figures for that switch - down at 12VDC my guess is that it would be OK up to 5A or 10A. Finding actual figures for your switch if used for 12VDC could be tricky, but my take on it is that the world will not end if you use it to switch 8A.

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## cherub65

Wouldn't you just switch the power (240v) to the transformer?

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## martrix

> Is that 12V AC or DC that you will be switching? 
> If AC, then for sure  no problem. 
> If DC, it is a bit more tricky to answer, but my guess is it would be OK. 
> The normal mains switches are rated for 10A 240VAC. Often you can see that without even pulling anything apart, with the rating being embossed on the rocker of the switch. Those are of course, maximum values. 
> When used at a voltage lower than 240VAC, the switch can still handle at least 10A. In fact, at lower voltages it can probably handle more than 10A. Good luck with finding the actual current rating at 12VAC, but since you don't need to switch more than 10A you don't need to worry about that. 
> The complication is that switches need to down-rated when used with DC (which is more prone to arcing than AC). Here are some actual ratings for a switch I happen to have here: 10A at 250VAC, but only 250mA (¼ amp) at 250VDC, or 500mA at 125VDC. I don't have any other figures for that switch - down at 12VDC my guess is that it would be OK up to 5A or 10A. Finding actual figures for your switch if used for 12VDC could be tricky, but my take on it is that the world will not end if you use it to switch 8A.

  yes thats why i thought i'd ask because of the arcing possibity, something I read. 
Yes its DC. Here are the specs of the LED, double it assuming there would be a 10metre length of leds. *Specifications:* 1)Working Input Voltage:* 12V**DC * *≥ 4A**/5 Meter* 2)Output power: *48W /5 Meter*3)Emitted Color: *Cool White* 4)Color Temperature:*6300~7000K*5)LED Quantity: *120 leds / Meter * 6)Luminous Flux:*550~600 Lumens/Meter*7)Viewing Angle :* 120°*8)Protection Rate:* (Non-waterproof)*9)Working Tempreture:* -20~50°*10)Warranty:* 1 Year*11)Package:* 5 Meters / Reel*   * 
Power Supply*  *Specifications:* 1)Type: *Power Supply Adapter*** *2)Input Voltage:AC100~120V 60Hz / AC220~240V 50Hz 3)Output Voltage: DC12V 10A 4)Output Current: 10A 120W (MAX) 5)Case Material: Aluminium alloy + Metal 6)Size: 199mm ×98mm ×48mm 7)Weight: 530g*

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## martrix

> Wouldn't you just switch the power (240v) to the transformer?

  That would require a qualified sparky. Plus I may want to switch some runs on independently.

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## chrisp

Have a look here http://updates.clipsal.com/clipsalon...s/A0000108.pdf and search for 30RSM2 or 30RSM3 (or just search for "d.c."). 
You may have to order these from an electrical wholesaler.

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## Bros

You do hear of the doom and gloom warnings about using domestic switches on low current DC but the results don't seem to bear this out. For many years we used wall plate switches for lighting, bilge pumps, ref on a boat with no disastrous results.  
Another example is 240v CB are commonly used in DC applications.

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## Ozcar

> doom and gloom warnings

  Hey, I said that the world would not end, not that it would! 
Just kidding...

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## Bros

> Hey, I said that the world would not end, not that it would! 
> Just kidding...

  I wasn't having a go at you.

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## stork955

Gday, wouldnt you still need to switch the transformer, as it will run all the time anyway? And to switch 12v, could you install an Automotive type switch in a blank wall plate? 
Cheers, 
Stork

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## BaysideNana

> Gday, wouldnt you still need to switch the transformer, as it will run all the time anyway? And to switch 12v, could you install an Automotive type switch in a blank wall plate? 
> Cheers, 
> Stork

  Not sure if my setup will work for you, but I bought some 12v LED waterproof strip lights to run underneath overhead cupboards in the kitchen, in hindsight I probably don't 'need' the waterproof option but it will be easier to clean as it's encased in clear PVC, specially near the rangehood.  The 5m strip of LED's came with a controller but no power supply so I bought a laptop transformer (brand new) for $20 as it had the same plug and amps needed.  The LED's are RGB and come with a remote control so you don't need to turn on/off at the power point....I had a double GPO fitted above the rangehood for this purpose and the tiny power cable can fit behind one of the overhead doors by adjusting the hinge a tiny bit.  Also could drill a hole through the base of the overheads and feed the wire through.  The remote control (as expected) does 64 colour changes and different lighting effects although I just plan to use plain warm white light.  I had to buy some 90deg fittings and soldered these into the strip to turn the corner with the kitchen bench.  A great DIY project that will look a million $$$'s.   
While I've had them working on the bench prior to final installation, then decided to put the house on the market so have put them aside for the next house.  Everything was bought on eBay from HongKong and total cost was around $90-100 (can't remember exactly, sorry) and to buy the equivalent here was way beyond my budget, unfortunately.  Sorry didn't take any photos on the bench before I packed them away.   
Sorry can't help with all the technical stuff above as I'm not a sparky, and why I used the laptop transformer plugged into a GPO.  Actually the builder's sparky tried to talk me out of the LED's because 'he' had never heard of them, although he agreed that what I planned was legal and above all, safe.... which is more than I can say about another GPO (with round earth pin) in a cupboard with bare copper wires visible which he installed!!  Due to the round earth pin it can't be used but seeing those bare wires makes me back away from it anyway.   
Hope this helps?

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## Smurf

> Another example is 240v CB are commonly used in DC applications.

   Common AC breakers lack an arc extinguishing mechanism. In short, if tripped under high load (which is the time a breaker should normally trip), the resultant arc may not extinguish. End result = fire. 
DC breakers connected backwards will have the same result. Unlike AC, it does matter which way around they are connected.

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## Crunchy

Switches have a rating that is a combination of its current carrying capacity and it breaking capability. 
The current carrying capacity is relatively straightforward and is a characteristic of the switch itself. 
The breaking capacity is somewhat more complicated and is also a function of the circuit before and after the switch. 
Breaking DC can be troublesome as any the inductance in the circuit makes it prone to arcing.  This is why it is difficult to say whether a standard switch will be okay or not, as we don't really have enough information to say. 
The safest thing to do would be to use a switch that explicitily states that it is suitable for (i) DC, (ii) the current anticipated, and (iii) the voltage intended to be switched.

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## martrix

> Gday, wouldnt you still need to switch the transformer, as it will run all the time anyway? And to switch 12v, could you install an Automotive type switch in a blank wall plate? 
> Cheers, 
> Stork

     
If im switching the 12v after the transformer, surely the transformer wont draw much power while the LEDs are off?  All sounding too hard and not worth it. If the job goes ahead I will just use one of  *these* in maybe a custom made wall plate or installed in the side of a cabinet below the benchtop.

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## Ozcar

It shouldn't really be hard. 
Maybe it was a mistake for me to raise the issue of DC vs AC in the first place. At only 12V I still can't see it being something to worry about, and Bros, who would know better than me, agrees with that. If you are really concerned, then some good alternatives were given, such as a mains switch with a 30A rating, or an automotive switch.  
Unless you have a particular need for the built-in indicator LED, or you just like the looks, then I don't see that the switch you linked to has any advantage over a garden variety mains switch. In fact, it is a step in the wrong direction as it is only rated at 10A 125VAC, not 10A 240VAC. 
The specifications you gave for the power supply did not say how much power it uses when it has no load, but it is probably not very high. It would be like having one more device in your house in standby mode, and maybe you worry about the power used by those, and maybe you don't. Provided the power supply has proper local approval, I don't see that you need to be too concerned about some small risk that it might catch fire if left turned on  your TV or microwave could do the same.

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