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-   -   Under Cabinet Lighting -- Where to put transformer? (http://www.diychatroom.com/f18/under-cabinet-lighting-where-put-transformer-123046/)

jmai14 11-10-2011 10:35 PM

Under Cabinet Lighting -- Where to put transformer?
 
I'm doing a kitchen remodel right now and trying to set up the under cabinet lights. I'm using xenon low voltage puck lights, which I want to hard wire to a light switch.

The lights I've purchased connect to the 14 gauge wire with a transformer, then low voltage wire runs from the transformer to the lights. The transformer connects to the 14 gauge wire with separate black/white/green wires. Basically my question is ... where should I put the transformer?

I see two ways to do this and I'm wondering what's best:

1) Put the transformer inside the junction box behind the wall, with the low voltage wire running through the drywall and to the lights.
2) Attach the transformer underneath the cabinet, with the black/white green wire running through the drywall and into the junction box.

Any third way I'm not thinking about?

I'd prefer to do it the first way, but I'm wondering if it's okay to have a transformer in a junction box. Also is it acceptable to run low voltage wire through the drywall like that?

BillyjoeAATech 11-10-2011 11:05 PM

Is it a plug in transformer or hard wire, either one you can try this, inside a cabinet ( top or bottom) cut in a plastic 4x4 or 6x6 j-box you van find it in the electrical department. Even though it is for outdoor use and weather proof it is perfect for the job, just onset the box into the wall that way your cover to the box is almost flush, therefore it almost hidden. And another thing you could do with low voltage lighting is you can put it on a wireless transmitter, Liftmaster makes a plug in remote and receiver kit, we use them on garage door kit too. you can plug your transformer directly into the receiver.

DIY kinda guy

pw5599 11-11-2011 12:56 PM

I'm doing a similar thing, adding under cab LED lights. I'm putting in 2 kits, each with 3 strips of lights and a plug in transformer. I'm putting a switched outlet above the cabinets then running the low voltage wire down inside a cabinet and out along the bottom. As far as I know you cant put low voltage wire inside a wall. I'll be putting in a small valence along the lights to hide them and the glare, and also hides the wires. The valence is going to go just in front of the strips about 8" from the front edge of the cabinets. I dont like having a front edge valence. I have checked with my inspector and it's ok to install an outlet above the cabinets for this purpose. That's according to CEC.

I'd just be guessing but I dont think a hard wired transformer can be inside a wall. I suspect it has to be accessible. Inside a cabinet should be ok. As always, check with your local codes and/or inspector.

One thing I like about LED lights, I've measured the amperage they consume on the 120 AC line. When off, the transformer takes about 1.5mA and when on, each set of 3 strips takes about 28mA, about 3.4W. With both strips on it's about 7W and thats so low that I could leave em on all the time and use virtually nothing for power :thumbsup:

darren 11-11-2011 01:46 PM

Quote:

Originally Posted by jmai14 (Post 768277)

1) Put the transformer inside the junction box behind the wall, with the low voltage wire running through the drywall and to the lights.

Is this junction box going to be accesable when you are done, it sounds like it is going to be hidden inside the wall. If this is the case you are going to have to do something differently to make the junction box accesable.

dmxtothemax 11-11-2011 07:16 PM

Why cant you put the tranny inside the cabinets ?
Tuck it up into the top corner,
Where it would be out of the way.

jmai14 11-12-2011 10:11 AM

Quote:

Originally Posted by darren (Post 768612)
Is this junction box going to be accesable when you are done, it sounds like it is going to be hidden inside the wall. If this is the case you are going to have to do something differently to make the junction box accesable.

Does the junction box have to be accessible? If so, then that means I have to put the junction box outside the wall, right? I mean where else could it go and remain accessible?

Then I guess my plan is to get a shallow 1-gang box and attach it either under the cabinet or hide it inside the cabinet. Then I'll just have the 14 gauge wire coming through the wall (or inside the cabinet) into the box, attach the transformer inside the box, and then run the low voltage wire down to the lights.

dsconstructs 11-12-2011 11:20 AM

You can run the 14 romex through the wall/through a hole in the cabinet and into a junction box mounted inside the cabinet. Has to be mounted in such a way that the romex is not exposed, so I run it through the backside of the box mounting the box directly over the hole. It's still accessible that way and cleaner than having the junction box under the cabinets.

darren 11-12-2011 11:54 AM

Probably to late for this but I have seen cabinets with a false bottom. Under the bottom shelve is a 3 or 4" space, this way you can recess your lights into the cabinet and have a place to hide your transformer and the wires for the lights.

Toofarfromfenwa 11-12-2011 04:34 PM

DO NOT EVER COVER UP A TRANSFORMER


Transformers heat up. They are stepping down something from 120 volts, to 12 or 24 volts. The electricity is dissapated through.......heat.

Don't EVER put the IN a wall, or in an attic. Mount them (if there's room) above the cabinets, where they won't be seen, or in a garage, or someplace like that.

DO NOT EVER cover them with ANYTHING.

CheapCharlie 11-12-2011 04:54 PM

Quote:

Originally Posted by Toofarfromfenwa (Post 769572)
DO NOT EVER COVER UP A TRANSFORMER


Transformers heat up. They are stepping down something from 120 volts, to 12 or 24 volts. The electricity is dissapated through.......heat.

Don't EVER put the IN a wall, or in an attic. Mount them (if there's room) above the cabinets, where they won't be seen, or in a garage, or someplace like that.

DO NOT EVER cover them with ANYTHING.

You are right about not covering up a transformer. But your explanation is not right. The voltage is not "dissapated through heat", it is converted from 120V to 12V/24V. Heat is created though, but it is not because of electricity dissapation.

Toofarfromfenwa 11-12-2011 05:37 PM

Quote:

Originally Posted by CheapCharlie (Post 769589)
You are right about not covering up a transformer. But your explanation is not right. The voltage is not "dissapated through heat", it is converted from 120V to 12V/24V. Heat is created though, but it is not because of electricity dissapation.

Yes, it most certainly is. Through "resistors". You put electricity under resistance, you create heat.

Every. Single. Time.

CheapCharlie 11-12-2011 06:41 PM

Yes, but in a transformer the resistance is inherant (sp?). It is not a conventional resistor that drops the voltage. I think I know what you are trying to say although your terminology is not correct.

bob22 11-12-2011 07:33 PM

http://www.explainthatstuff.com/transformers.html

"So a step-down transformer with 100 coils in the primary and 10 coils in the secondary will reduce the voltage by a factor of 10 but multiply the current by a factor of 10 at the same time. The power in an electric current is equal to the current times the voltage (watts = volts x amps is one way to remember this), so you can see the power in the secondary coil is theoretically the same as the power in the primary coil. (In reality, there is some loss of power between the primary and the secondary because some of the "magnetic flux" leaks out of the core, some energy is lost because the core heats up, and so on.)"

jmai14 11-13-2011 10:49 AM

Ok so I'll need to put the junction box somewhere outside the wall (maybe hidden in the back of the cabinet). Then the transformer will need to be outside the junction box and presumably hidden as well (I'm thinking under the cabinet). Any issues with that plan?

Toofarfromfenwa 11-13-2011 03:09 PM

Quote:

Originally Posted by jmai14 (Post 770125)
Ok so I'll need to put the junction box somewhere outside the wall (maybe hidden in the back of the cabinet). Then the transformer will need to be outside the junction box and presumably hidden as well (I'm thinking under the cabinet). Any issues with that plan?

None whatsoever. As long as the transformer is accessable and it is not buried somewhere, you're good.


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