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Apparent electrical current through laptop case and other equipment

Apparent electrical current through laptop case and other equipment

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Old 06-20-14, 12:24 PM
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Apparent electrical current through laptop case and other equipment

Here is the problem: I use my laptop in an office / shop space of my home. My laptop has a metal case and when I run my fingers across the top of the laptop it feels like there is a current happening. If I am in bare feet I can get a slight shock. I am re-placing and re-wiring the new recepts in the room. I have come across a condition that seems a little odd since I think the recepts are wired in series: one of the hot legs is black and the other brown! and as I would expect each blk / brwn wire is associated to a wht wire. And I have two separate grnd wires and a hot wire is associated with each. What I want to do is wire all the recpts in parallel rather than series. Is that an issue? I know I need to keep the yokes in place so the top and bottom of each recept works. This is a 20 amp circuit and if I wire in parallel does this compromise the 20 amp circuit? Or does the same loading factor still apply? I'm hopping this will resolve any open grounds or faulty circuit issues. Any thoughts?

I'm wiring in a 30 amp circuit for a specialty drilling mill. But for now I have it pugged in to the 20 amp circuit. I do not run anything else when the mill is running except for a small shop vac. Am I playing with danger?

I should mention my service is a new 200 amp service with all new breakers. I feel certain the breaker will trip should things get over loaded. I know for the mill the 30 amp is for initial start-up. That is why I turn the mill on first then the vac.

Thank you for any advise,

JRB
 
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Old 06-20-14, 02:48 PM
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Welcome to the forums! Your key words "shop" space tends to indicate a concrete floor. If so all your receptacles should be GFCI. If you have the dedicated circuit for the drilling mill, why are you using a 20 amp receptacle. The plugs are totally different. Is it 120 volt or 240 volt machine? Can it be converted to 240 volts? What is the nameplate rating of the mill?

A tingle from static electricity is to be expected to an extent. Ensure your grounds are continuous to the panel and then to the grounding rods. I wouldn't run the mill, vacuum and computer from the same circuit. You will have surges that your computer doesn't need.
 
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Old 06-20-14, 04:05 PM
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There is no way the outlets are wired in series,are these outlets wired with conduit between them sounds like they are when you say there is brown wires there,can you exclude a pic of the inside of that box looks like.
Geo
 
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Old 06-20-14, 04:43 PM
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Most laptops I have seen use a separate power supply that feeds the laptop with low voltage DC. What does the connector to the laptop look like? It might not have a ground so that might not be even the issue.
 
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Old 06-20-14, 06:41 PM
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Thanks for the feedback. Yes the floor is slab on grade. And the current wiring is series.
I am using the 20 amp circuit for the mill until i can get the new circuit installed. I am replacing the current receptacles and thought if i do it all in parallel it would solve the open circuit or ground issue. Are there any issues
if i rewire the receipts in parallel? I know there is the additional wires at each box.

Thanks again for all your questions and advice. The mill is 120 V.
 
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Old 06-20-14, 06:53 PM
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And the current wiring is series
No, it is not. There is no normal wiring in any house in the US is wired in series. If it was it would not work. What you think is in series is actually called daisy chaining. Your "brown" wire might just be a dirty white.

Rewiring will not change your grounding issue. How are your receptacles wired now? Is there a ground wire in the boxes? Are they wired with steel conduit or metal cable?
 
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Old 06-20-14, 06:57 PM
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So if the outlets are in series you basically need something plugged into each outlet to complete the circuit ,is that what you really have?
Geo
 
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Old 06-20-14, 07:20 PM
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The current condition is series (daisy chained). I've tested the current between wires and the brown wire is hot. The existing wiring is romex. And there is a continuous ground. I checked the lugs at the main and everything is tight. Grounds all look good. The outlet tester does not show an open ground. I'm going to unplug devices to see if that reveals anything.

One thing I think is going on is the brown wire has an insulated ground so that may be the problem. I think there are one of two things happening: an open circuit or ground. Or a device is feeding back through the system - is that even possible?
 
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Old 06-20-14, 11:23 PM
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Is your laptop charger's ground prong in tact and plugged into a grounded receptacle? When I use my laptop with a cheater plug I get shocked off it. Interestingly enough, it has never tripped a gfci. (Plugged into one now)
 
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Old 06-20-14, 11:55 PM
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A picture of the wiring would be really helpful. I've never seen romex with a brown wire in it. The colors should be black and white (and red if three wire) and a bare ground wire.

As romex gets older and especially if it's been used in high current draw applications..... the white can turn to a brown color from the heat.

Using a meter......
You should measure 120vac from black to white.
You should measure 120vac from black to ground.
You should measure 0 from white to ground.

http://www.doityourself.com/forum/el...-pictures.html
 
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Old 06-21-14, 04:59 AM
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I just had a service call with a similar issue. The customer had "someone that new a little about electricity" do a service upgrade.

Upon investigation, the neutrals from the 3 wire range and dryer circuits were tied to the ground bar and the bonding screw wasn't installed in the panel which resulted in stray current, even on the coax cable.

Since you mentioned the service is new.
 
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Old 06-21-14, 09:36 AM
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Ok, we have a few terminology issues before we can continue:

The current condition is series (daisy chained)
Your wiring is in parallel, not series. If it was in series, things would not work. please looks at some diagrams on the internet. Even if the devices are direct wired, two wires on the hot and neutral side, they are still wired in parallel.

One thing I think is going on is the brown wire has an insulated ground so that may be the problem
This makes me think you care calling a cable a "wire". A wire is a conductor with, or without, insulation. A cable is an assembly of wires surrounded by an overall jacket that can be metallic or non-metallic.

You need to test the wires with a meter as PJ has posted.
 
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Old 06-21-14, 12:59 PM
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Thanks Tolyn Ironhand 0 my terminology was in response to several of the messages. I agree with you btw - my use of each term was mostly the application of the wires to the recept.

That said here are some photos. And the results of testing with my voltage meter (a Klein btw).

The Yellow wire nuts wires give ~ 120 V reading with the grn giving 104V(!)
I thought this should be 120V
The Yellow neutral to grn reads +/- 3V (!) - I thought this should be 0
The Orange do not provide any readings.

As you can see the brwn sheathing is brwn. And I believe this is wired to the last recept in the space.
 
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Old 06-21-14, 01:16 PM
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Where are you getting yellow and orange? You are using a digital meter and getting phantom voltages. What is black to ground? Black to lower right white? You have a combination of romex and conduit, thus the brown wire. What voltage from brown to ground, and brown to lower left white, using your picture for reference.
 
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Old 06-21-14, 01:17 PM
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Another photo of the wires - the colored wirenuts depict the associations. At least as I have tested them with my volt meter.
 
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Old 06-21-14, 01:19 PM
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New (correct photo) changed reply.
 
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Old 06-21-14, 01:20 PM
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sorry chandler - I was having problems getting the image to load. But to answer your question - in the second image I placed wire nuts on the wires as I was getting reading. And since I am getting current through the wht to grnd test I keep thinking I have a crossed grnd somewhere. Is that how you would read it.
 
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Old 06-21-14, 01:20 PM
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It appears you have two cables in that box. It also appears that the cable on the right might be UF. which is not normal, but I have seen before. People just use what they have on hand.

I see no yellow wire nuts so please measure these and post what you get:
Cable on right:
Brown to white
brown to ground (bare)
white to ground

Cable on left:
White to black
I do not see a ground but if there is one:
White to ground
Black to ground

Now measure cable to cable
Left black to right ground
Left black to right white
Right brown to left white.

** edit ** I see the nuts now. You can test from them like you did, please do above so we can get the full picture.

And since I am getting current through the wht to grnd test
You are measuring voltage, not current.
 
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Old 06-21-14, 01:25 PM
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I am getting current through the wht to grnd test
As Larry said:
You are using a digital meter and getting phantom voltages
Best to use an analog multimeter. (A cheap one will be fine).
 
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Old 06-21-14, 01:27 PM
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The wire to the right of the blk wire has a brwn sheathing. And without removing drywall I do not know if it is in conduit or a metal cable. However, since I have this off circuit - I am still getting the electrical feedback through the laptop case. I've tested the laptop in other outlets in the house and that problem does not happen. That is why I think it is isolated to this circuit or part of the house.

I have three other outlets to evaluate. Perhaps I can find the cross up.

Do you guys ever have this kind of bug hunt?
 
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Old 06-21-14, 01:30 PM
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Ray, what would be an analog unit. I went to Home Depot to get the one I have and may have been looking at analog and did not realize it.
 
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Old 06-21-14, 01:37 PM
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An $8-$15 one will do all you need to do.
 
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Old 06-21-14, 02:09 PM
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Here is an image of the wires as tested

Yellow Group:

Blk to Wht - 118 to 120 V
Blk to Orange Wht - 104
Blk to Grnd - 55 V
Blk to Orange Grnd - 101 V
Wht to Grnd - 63 V
Wht to Orange Grnd - 3.2 V

Orange Group:

Brn to Wht - .03V
Brn to Yellow Wht - .7 to 3V
Brn to Grnd - .03V
Btn to Yellow Grnd - 57V

I'm leaving to get an analogue volt meter
 
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Old 06-21-14, 03:15 PM
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Blk to Wht - 118 to 120 V
...
Blk to Grnd - 55 V
...
Wht to Grnd - 63 V
That is enough to say that you have an open ground feeding this outlet. Yes, the ground readings are most likely phantom voltages but you don't get phantom voltages like this if the grounding wires are connected properly.

You need to trace this cable back to the panel. As was mentioned maybe the (main) panel itself is not bonded properly.
 
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Old 06-21-14, 04:17 PM
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Thanks Astuff, I checked the buss bars but I did not trace the cable. Thanks.
 
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Old 06-22-14, 12:16 PM
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First I want to thank all of you for the helpful information. I found the fundamental problem outlet. It was the one at the end of the string! I am going to post a photo of the outlet so you can see what I am talking about.

The brn wire and sheathed grnd wire on the box I have been showing came from this last box. I could kind of see the cable and it was blue not white or black. There is no grounding lug for the outlet; the ground was tied to the box. Once I replaced this outlet and reconnected the other the electrical feedback through the surface of the laptop and the milling bed are gone.

However, when I used the outlet tester I am now getting an open ground error. So I am going to go through the remaining outlets to for all the recept / wiring connections.

An electrician friend is going to help (direct me) for wiring the 30 amp circuit. I've done stuff like that in the past but I want expert advice. That is part of the reason for my post here.

After getting the 30 amp circuit in I need to tackle the wiring for the range. The range is electrical and the wired condition is direct connection with no j-box. So much for home inspections! I'll be wiser next time! But it is what it is.

Again, thank you for the great questions, education and advice. Anything else you might want to pass along, please do.
 
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Old 06-25-14, 08:24 AM
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Follow-up: After I thought I had fixed the problem I was still getting the electrical issue through the laptop cases. After checking all the wall recepts I was getting positive feedback from the recept tester. Except for one condition which displayed an open ground. It was at the recept at the end of the string - I thought maybe I had wired the recept incorrectly.

I found the recept with the broken ground. It was deep in the box and not obvious because of the way the original recepts were wired. The recept was the second one in the string.

NOW all tests are working correctly. I'm getting 120 V at all boxes - whohoo!

To all you professional electricians - my hat off to you! You guys earn all that you get. Thanks again.
 
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