wiring under cabinet led using pre existing switch

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  #1  
Old 03-18-16, 09:33 PM
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wiring under cabinet led using pre existing switch

Hey guys! first time here and glad i found this forum.

I m trying to DIY under cabinet lighting using my preexisting bulkhead light switch. So I took the switch out a bit and measured the voltage, it turns out it is 240VAC... is this even possible? The switch is located beside the sink and beside the switch is a 2-outlet with 120VAC. The question is, can I do something about it so that I can use my 120VAC input LED driver?


Thanks guys!
 
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Old 03-18-16, 10:18 PM
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How did you measure voltage at the switch. You can't just measure between the screws on the switch. if power comes into the switch you disconnect the black of the power in cable and measure from neutral to ground. If this is a switch loop there is nothing to measure at the switch.

What did you use to measure voltage?

Tell us about the wiring at the switch.
 
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Old 03-18-16, 10:40 PM
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Hi, I used my voltage meter and yes I measured at the screws and took the ground off the outlet beside it (convenience).

There are just 2 white wires connected to the leviton decora switch (right side) and no ground connected to the green screw. I will try to take a picture of it tomorrow and post it here if that helps.
 
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Old 03-19-16, 12:02 AM
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There should never be two white wires connected to a switch so pictures would help. http://www.doityourself.com/forum/li...rt-images.html

Analog or digital multimeter?
 
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Old 03-19-16, 12:56 AM
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yeah 2 white wires.. i will take a pic tmrw..

digital multimeter
 
  #6  
Old 03-19-16, 09:44 PM
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This is weird, I put my -ve to the ground outlet and it shows 120VAC but when I put it at the screw, it reads 240VAC
 
  #7  
Old 03-19-16, 09:57 PM
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What you are measuring on the last image is wrong.
The switch and outlet must be powered from different phase. You are measuring voltage across L1 and L2 which will give you 240V.

You measured 120V between hot of the switch and ground. So, yes you can use 120V LED light. Truly, you should be measuring voltage across hot and neutral, but neutral is tied to ground at main panel if properly wired.

One of the wire wires on the witch is wire nutted to a black wire. That black wire must been too short and had to be extended. It should been extended with black wire, but guess it is ok since you can see where it went.
One issue I see is that they used drywall screws instead of proper #6-32 machine screws and don't see ground wire going to the switch. Normally, it will be grounded through metal junction box (assuming it is grounded correctly), but I don't think drywall screw makes a good conductor.
 
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Old 03-19-16, 10:46 PM
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sonofagun! paid a lot for this "certified" electrician to change this switch to the decora (we are renovating our kitchen) and i noticed the bottom cable of the outlet is not shielded with anything, I see like a bare metal that the "certified" electrician used. Is this ok?
 
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Old 03-19-16, 11:28 PM
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i noticed the bottom cable of the outlet is not shielded with anything, I see like a bare metal
Are you referring to bare copper wire connected to a green screw?
That is ground and bare copper is perfectly fine. Since you have metal junction box, this bare copper wire should be connected to the junction box first, then to switches and outlets. When self grounding switches or outlets are used, you don't have to connect separate ground wire as they are grounded to the junction box through screw.
If you look at your switch, you will see a small copper clip on one of the mounting hole. That is self grounding. It holds on to the mounting screw providing a ground connection. My concern is that drywall screw has black protective coating which will act as a insulator.
Should have used #6-32 screws. Outlets and switches come with screws already, but often they are too short and have to change with longer screw. Using drywall screw will enlarge mounting hole on the junction box and you may not be able to use #6 screw anymore.
 
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Old 03-20-16, 01:08 AM
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hmmmm ok i will check it out tomorrow

but thanks for the clarification, i will go ahead and install the led light now!
 
  #11  
Old 03-21-16, 12:42 AM
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You mean this screw?
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So I tried to install my LED driver after hours of fishing the line into the electrical box, and tried to connect it according to the wiring diagrams (https://www.ledworld.ca/product/powe...r-e40l12dc-ko/

So i connected the black wire from the LED controller to the black wire that is connected to the top of the leviton decora like shown
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And then I connected the white wire from the LED controller to the black wire that is connected to the bottom of the leviton decora (can be seen from the photo above) <-- it made the bulkhead light dim when I tried to turn if off using the switch, and no 12VDC reading from the LED controller.

Then I try to connect the white wire from the LED controller to a bunch of white wires (I m assuming they are neutrals) and the bulkhead light acts normally but the 12VDC reading was 18-19VDC which is too high for the led strip lights isnt? The wire that I fished out is the top left corner of the electrical box.Name:  20160321_005119.jpg
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What did i do wrong?

P.S. All the pics should be 90degrees clockwise rotated.
 
  #12  
Old 03-21-16, 06:14 AM
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Did you connect your power supply between 2 terminals of the switch?
That is wrong.

First, you have to find which terminal of 2 is always hot (power) even with switch off. The other terminal will be hot only when switch is on and wire connected to this terminal is the wire going the existing light. This is the wire you want to connect black wire (hot) going to LED power supply.
For white wire (neutral), look for white wire that comes from same cable black wire form above goes. It should be wire nutted to another white wire (from power side) in the junction box. This is where you should connect white wire for LED power supply.

As for 18~19V output from LED power supply, if it is a LED driver that is correct, but meaning less reading.
LED drivers are constant current (not voltage) power supply. It will increase or decrease voltage to keep the current constant. LED is a constant current device, so this type of power supply is better and keeps brightness constant without caring too much about how many LEDs are liked in series.

DO NOT connect LED with power supply on. Depending on the power supply, that can fry your LED. Without load on the power supply, power supply will just putout maximum voltage because there is no current flowing. There should be a load on power supply first for power supply to adjust its voltage.


Screws I'm talking about looks something like this.
http://ecx.images-amazon.com/images/...lL._SX522_.jpg

Size will be #6-32, and you can easily find them in hardware stores.
 
  #13  
Old 03-21-16, 10:06 AM
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Then I try to connect the white wire from the LED controller to a bunch of white wires (I m assuming they are neutrals)
You can't assume. There are two different branch circuits in that box as evidenced by the 240 volt reading. Neutrals of two different branch circuits can not be connected together. If that switch is a switch loop then there is no neutral for the light circuit in the box. If that is the case the driver can not be powered from the switch box as wired.

This is a long confusing thread. I haven't read it all but before you stared working with the switch was a single 2-wire cable hooked to the switch? If so it is a switch loop. If it is a switch loop the driver can not be powered from there. There is no neutral.
 
  #14  
Old 03-24-16, 10:26 PM
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Got it! will post the project outcome when done !

Thanks you all! this forum rocks!
 
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