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Electrical Wiring Question


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#1 of 4 Johnny Angell

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Posted March 06 2011 - 08:07 AM

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I short while ago we accidentally pulled an alarm down to change the battery.  One of the white wires came loose.  Above on the top you see a picture of another identical alarm wiring with all wires attached.  In this one, there are 3 orange caps.  1 each with 3 black, 3 white, and 3 red wires all attached.  One each of those colored wires comes from the plug (hanging at the bottom) into which the alarm is plugged.


I thought this would be a template to help me understand where to put the loose white wire.  But in the picture of the loose connectin on the bottom, There are still 3 red, black, and white wires in each of the orange caps.  So where do I put the loose white wire?  BTW, don't let the fact that the builder partially painted the wires.  Those 3 orange caps still just have 3 of one color in each cap.


If this is sounding like I don't understand electrical wiring, you are correct in getting that impression.


BTW, what kind of juice are we dealing with here?  Do I need to turn breakers off to repair this?


Johnny
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#2 of 4 Edwin-S

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Posted March 06 2011 - 08:52 AM

You are dealing with 120V AC. The best thing to do is turn off the breaker when dealing with electrical repairs. Generally, the white wire is the neutral wire, so it would be tied in with all the other neutrals, in this case the cap with the other three white wires.


Edit: I should clarify something here. Judging by the photos the circuit wiring is a 120/240V, 1 phase, three wire circuit. This means that the red wire and the black wire are both hots, while the white wire is your neutral. If you use a digital multimeter, set to AC volts, and measure between the black wire and the white wire, the voltage will be 120V. The same will be true if you measure between the red wire and the white wire; however, if you measure between the black and the red, the voltage will be 240V. In the case of your detectors the voltage will be 120V because the neutral (white wire) is being used as a return. Whoever wired your place probably wired using this method because it saves on wire, since he is most likely using the red wire to provide power to other loads on the circuit. I'll also qualify this by saying that I'm not an electrician, my diploma was in electronic controls and automation, so if you feel uncomfortable with this explanation by all means consult with one of your local electricians.


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#3 of 4 Johnny Angell

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Posted March 06 2011 - 12:41 PM

Are you saying that white wire was always loose and not connected to the other whites?  The bit about saving on wire, I can believe because the builder took every short cut he could.


Johnny
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#4 of 4 BrianW

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Posted March 07 2011 - 02:21 PM



Originally Posted by Johnny Angell 

Are you saying that white wire was always loose and not connected to the other whites?

No, the white wire must be connected for the unit to work (battery notwithstanding).


As Edwin said, switch off the breakers.  It looks like you will have to switch off two breakers to make this J-box safe.




Lowe's sells a device that looks like a large pen with a (generally) yellow point that detects whether AC wires are hot without making electrical contact.  When you put it near a hot wire, it will beep until you move it away.  If it doesn't beep, then the wire is safe to work with.  Buy this device, and use it to locate the breakers, and don't work on it until you know the breakers are off.

And when you use the device you just bought, check it with a live wire to be sure it's working before you trust its silence (Is it turned on?  Is its battery fresh?) to indicate a non-hot wire.

The hot-wire detector is handy to have since it can be used to check outlets and extension cords and appliance/lamp power cords.




Once you've done all that, connect the white wire to the wire-nut (that's the orange thing) in the back of the picture -- the one partially obscured by the black wire.  And you can't just poke the wire in.  You'll need to unscrew the wire nut, re-twist the white wires together (use pliers for a good twist), and then twist the wire-nut back on.  Righty-tighty, lefty-loosey


Also, as Edwin said, if you're not comfortable doing this, consult an electrician.  (Or a neighbor you don't particularly like.)



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