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Socket fried after plugging in electric charger


wyt168's Avatar
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11-13-17, 03:38 PM   #1 (permalink)  
Socket fried after plugging in electric charger

Recently got a Nissan Leaf and it comes with a 120v "trickle" charger.
I used it on a electric socket in my garage to charge the car overnight. It worked for about a week and stopped working. Used a lamp to test it and it didn't light up.
Here's a few things I noticed:
--all other outlets in my garage are not affected. I have a frig that's connected to another outlet, which is working fine, as is the ceiling light, and garage opener.
--no switch was tripped in my junction box.
--I measured the voltage between the N-H-G wires using a digital multimeter; here's what I got:
H-G: 124v
H-N: 59v
N-G: 5.9v
--I also took the cover off the socket, and checked the wiring to the receptacle. All wires (black, white, and bare) are securely fastened to the screws of the receptacle and I fastened them again.
I've browsed some forums and got nowhere.
Someone help me here!

 
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11-13-17, 04:53 PM   #2 (permalink)  
Welcome to the forums.

Your testing has demonstrated an open neutral. If that is just a single two wire cable there..... you'll need to find out where it comes from. More than likely the neutral is broken at the source.

Check back to the nearest device on the same circuit.


~ Pete ~


Last edited by PJmax; 11-14-17 at 12:19 AM. Reason: correction
 
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11-13-17, 11:08 PM   #3 (permalink)  
Hi, Pete:
Thanks for the reply. I will check for loose connections at other places--there is a switch right next to the socket--however the switch controls a light outside the garage, and the light is working though. Would a light still work if a ground or neutral wire is loose or disconnected?
If that is just a single two wire cable there....
Not too sure what you mean here (I'm a newbie here so not too familiar with the terminology). It is a 3-wire socket with neutral, hot and ground wires, if that's what you are referring--so it's 3 wires.
You first refers to an "open ground", which I take as that the ground wire is loose or broken somewhere. Then you mentioned that it could be that "the neutral is broken". So I am a little confused.
As I mentioned earlier, all other sockets and switches seem to be working though. So I don't know where to check?
Any hint where I should start looking?

 
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11-14-17, 12:29 AM   #4 (permalink)  
Wow... I am sorry. I corrected ground with neutral.

With home electrical wiring..... in particularly non metallic cable..... the ground is not counted.
A two wire cable is white, black and ground. It's called 14-2 w/ground
A three wire cable is white, black, red and ground. It's called 14-3 w/ground
(I just used 14. There are other sizes like 10 and 12)

If you have three wires in that box you have a single two wire cable. That means that is the end of the circuit. The circuit doesn't pass thru there on it's way to another location. Your receptacle could very well be connected in the switch box.

The easiest way to find a problem is to identify everything on that circuit. The circuits originate in the panel and then go out to their different locations. Wiring is usually done in order from beginning (the panel) to the last device on the circuit. So if you know everything on the circuit..... work your way back towards the panel. You'll have to check every box on the affected circuit for the problem.

Since power comes into certain boxes and passes thru...... that device could work normally but the wire leaving there is not connected properly.

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~ Pete ~

 
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11-14-17, 12:13 PM   #5 (permalink)  
Wow, Pete: this really helps, esp with that diagram!! Thanks a lot!
So this wall receptacle could very well be the last device on the circuit. It turns out if I turn off the switch in my switch box that controls this branch of circuit that involves this receptacle, the lights in my guest bathroom and the outlet to which I connect my TV/stereos are also out, but the bathroom lights and TV, etc are all working.
So the switch next to this receptacle could be the culprit (I hope), I will for sure check it when I go home.
One more question: why there is a voltage between H and N (59v) and N and G (5.9v) when there is an "open neutral"?

 
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11-14-17, 12:44 PM   #6 (permalink)  
One more question: why there is a voltage between H and N (59v) and N and G (5.9v) when there is an "open neutral"?
Probaly using a digital meter. They tend to be influenced by nearby voltage. That's why we recommend an analog meter.


I can explain it to you, but I can't understand it for you.


Last edited by PJmax; 11-14-17 at 05:28 PM. Reason: fixed quoye
 
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11-14-17, 10:51 PM   #7 (permalink)  
Probaly using a digital meter. They tend to be influenced by nearby voltage. That's why we recommend an analog meter.
Interesting! Didn't know that. I happen to have an analog multimeter lying around. I will use that to check the voltage between the wires and see if there is any difference.
Thanks for the note.

 
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11-15-17, 11:42 PM   #8 (permalink)  
Hi, Pete:
You are exactly right! So it is the switch (it controls a light outside my garage) that is next to this receptacle which is the culprit!
This is simple 2-wire switch (a photo of the wiring to the switch is attached). Inside the junction box, it looks all wires terminate here. The nut that connects (or joints, I am not sure if I used the right word here) 3 (or 4) hot wires partially melted. So are the plastic sheath for the wires.
Obviously pretty intense heat there, but I am not sure the reason that cause it. Could it simply be the load? I plugged in a car charger in the receptacle which is fine. But somehow it caused the wire here in this switch box to melt.
I hope I can get some explanations from you guys why and what has caused it to melt and what I should do to fix this problem. Before I understand what has possibly caused it, I don't want to touch it.
p.s. I tried to attach a few pictures I took of the switch and the melted wires. However it appears to be much involved than I first thought. I will attach the pictures whenever I figure it out.


Last edited by wyt168; 11-16-17 at 12:31 AM.
 
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11-15-17, 11:53 PM   #9 (permalink)  
Hi, Ray:
You are right. When I used an analog multimeter, the reading are different.
H-G: 125v
H-N: <1v
G-N: 0v
So two out of three readings are wrong when I used a digital meter, esp. for the voltage between H and N wire--the digital meter says 59v. Why is that? Why are other readings not affected?
The voltage between H and N in a correctly connected circuit should be around 120v, right?
Is this why Pete can tell that there is an "open neutral" in the circuit?

 
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11-17-17, 03:32 PM   #10 (permalink)  
Hi, Pete:
Thanks for the instruction on how to upload and attach pictures to posts.
I have uploaded two pictures: one showing the wires to the back of the switch, the other one shows the melted wires. It looks like the hot wires, 3 or 4 of them tightened by a wire nut.
Now the question is: does it look like that there is something wrong with the way they are connected? What could be the possible causes for it to melt? I worry that if I reconnect them again using a wire nut, it might melt again. What can I do to prevent it? In a word, I would to find out the root cause for this, understand why it happens before I mess around with it.
Thanks.

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11-17-17, 07:47 PM   #11 (permalink)  
does it look like that there is something wrong with the way they are connected?

You may have some loose connections within the wingnuts, but the most obvious problem is the back stabbed switch. Move the wires on the switch to the screws. I would also remove the wingnuts and replace them with new ones and make sure the connections are tight and secure.

 
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11-17-17, 08:47 PM   #12 (permalink)  
Definitely check the white and black connections. Replace both wirenuts.


~ Pete ~

 
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11-18-17, 10:00 AM   #13 (permalink)  
Any loose connection with a load placed on it will heat up. The greater the load the higher the heat. Any arcing will pit the connection and exacerbate the issue.


All answers based on National Codes. Please check with your local building departments for local amendments.

 
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