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Old 04-25-2016, 01:58 AM   #1
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Default Phantom Voltage?

Hi all, first post...will start by saying thanks for all who have a willingness to share wisdom and help other sparkys out...super appreciate it!!!

Ok so I will try to keep this short...

My aunt calls me and says her brand new pool sweeper stopped working and the tech came out and said the motor burned up. They replaced it and all was good. Then a little while longer it stopped working again and they wanted me to test the plug before they called the company again. I will fill in the details of my troubleshooting but at this point the tech came back out and said the brain of the machine was no good which could have caused the motor to fry as well.

So I go out there pull out my fluke 179 and test hot to neutral...119v. Then I test ground to hot...42v. Ground to neutral...86v. Ok so I start trouble shooting the circuit....neutrals at the main are all good and snug. I turn off the circuit to see what else is on it and it has bathroom lights and plugs, master lights and plugs, hall light, outside gfci plug, and outside flood light. I begin to open up switch boxs, and find that the handyman (brother in law) who did a huge remodel on the whole house switched all the neutrals instead of the hots. I checked a light and it was wired properly but the neutrals were on all the switches...and same voltage reading as the gfci plug outside the pool sweeper was plugged into. I proceeded to rewire all the switches and and checked the plugs. All the plugs were correct including the gfci and when I got everything back together I tested the GFCI again.

hot to neut...119v
ground to hot...107v
ground to neut...11v

better but still not good. there were no other switches on that circuit so I assumed a possible j-box in the attic. So i went back today and jumped in the attic...this is what I found.

The circuit starts at the main panel with a 14/2 then hits a j-box where it wire nuts to the old knob and tube wiring that was original in the house. It looses the ground at that point and then had a couple taped up splices and then hits the hall light and is spliced back onto another 14/2 which then hits a j-box. From there 3 14/2's are spliced on and go to various switch and plug box's. to simplify...

main---14/2---jbox---nob &tube (no ground)---splice---splice with hall light---splice with 14/2...jbox---14/2 to switch/plug box's.

At the jbox where 14/2's are spliced and go down the walls' grounds are wire nutted together as well as neutral and hots as expected.

After doing more testing I discovered that if all the lights on the circuit were off then ground to hot was closer to 119 and ground to neutral was closer to 0. But as I turned more things on then voltage on hot would get less and voltage on neutral would be more.

so after discovering the grounds were broken in the attic (where the knob and tube portion was) I decided to run a separate ground from the main panel into the house to make sure I didnt have a ground issue. Well when I did that I discovered my hot had a constant 119v, neutral had anywhere from a few hundred mv to 2v on it...and my ground had up to 50v on it depending what I turned on.

I began isolating my grounds working back to the jbox in the attic and got to where the 14/2 from that jbox (where the grounds start) down to a non gfci bathroom plug (not counter top plug) was getting 44v on the ground with all wires isolated at the plug and all ground isolated at the jbox. So i isolated the hot for that wire at the jbox as well and as soon as I disconnected it from the incoming hot the voltage on the ground disappeared. I checked continuity between the ground and hot and neutral and got nothing. If i hooked just the hot up in the jbox (so it was just the line coming in and the 14/2 going down to the plug, all others were isolated) and the neutrals were all tied together , grounds were isolated, i would get 44v on the ground at the plug.

Is this just a phantom voltage? I put everything back together and again I get between 10v and 50v on the ground depending on what else in the circuit is on. If its a phantom voltage then why did the pool sweeper die? Coincidence? I am going to run a 14/2 in the attic next weekend to eliminate the knob and tube portion and allow the ground to travel back to the main but where is the voltage coming from and how can I verify the plug is safe to use? Just run the ground back to the main test for voltage on the ground and call it good?

ok that was super long but more details the better I hope! let me know what you thing so I can get this sorted out in my head. Thanks ahead of time for your help!!!!
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Old 04-25-2016, 02:55 AM   #2
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You say your brother-in-law did some "remodeling"? I take it he's not an electrician? The 86v G to N is a clue. I would investigate a neutral issue, especially with knonb-n-tube to NM, and back. And I would use a wiggy.
And, welcome to the forum.

Last edited by joebanana; 04-25-2016 at 02:58 AM.
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Old 04-25-2016, 04:20 AM   #3
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Welcome to the forum..

I agree with Joebanana about the voltage on G-N situatuon and yuh use the wiggy to verify it due some digutal voltneter can pick up panthom voltage ..

I would just ditch the T&K it is alllready comperised behond being salaveable .. So run the nee NM cable and make the proper connection.

The pool side should be on it own circuit ...
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Old 04-25-2016, 01:41 PM   #4
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Thanks guys, I will eliminate the k&t and test with the wiggy. I ran a new feeder for the pool equipment out of the main and installed a pool panel for them but the sweeper can't reach the other side of the pool from that location. I think they are going to redesign it later so it will eventually be on its own circuit but they were using a closer plug on the side of their house for the time being. Right now they have it on a extension cord to reach the pool equipment. And yes... my aunts brother in law is a handyman at best. He does it all and most of it is pretty hoaky. They are not using him anymore as this is just the end of a long line of problems they have had with him.

Anyways thanks for the help, I will make the fixes next week and report back with the results.
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Old 04-25-2016, 03:11 PM   #5
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As was stated the pool should be on its own circuit. The k&t is a mess demo it.
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Old 04-25-2016, 03:16 PM   #6
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Make sure there are no motors online when you are testing as well , ceiling fans ,pool heater etc. these can give you bogus neutral readings that circuit is very corrupt.
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Old 04-25-2016, 08:24 PM   #7
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I think all your reading issues are related to a floating bond. Your neutral
and hot seem to be fine. Protect the whole cct with a GFI or add a bond
throughout ->either one is to code here but you'll need to verify that's also
the case in CA.
Of course, replacing all the K&T with NMD90 would be best.
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Old 04-25-2016, 09:05 PM   #8
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Couple other things popped into my head:
1) Switching the neutrals is a no-no but has no bearing on the meter
readings. Nor will it interfere with proper circuit operation.
2) K&T is unlikely to cause problems as long as it's left alone. My biggest
concern, by far, would be transitions between K&T and newer wiring.
3) Pool sweeper issues are most likely coincidence.
4) Fixing things after a DIY'r has f'd it up is tedious.
5) I have to get another beer.
P&L
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Old 04-25-2016, 09:14 PM   #9
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Yea...it's not the first thing of his I have fixed...and probably won't be the last. But not looking forward to the attic crawl again to run the nm next week. The jbox is in a place where I can barley squeeze into and pretty much have to wedge myself between a beam he added and the rafters. I get stuck right at my hips which is just enough for me to access the jbox!!! It's fun!!!! The outside plug that the pool equipment is plugged into is a gfci so hopefully the sweeper was coincidence.
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Old 04-25-2016, 10:20 PM   #10
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Quote:
Originally Posted by PlugsAndLights View Post
Couple other things popped into my head:
1) Switching the neutrals is a no-no but has no bearing on the meter
readings. Nor will it interfere with proper circuit operation.
2) K&T is unlikely to cause problems as long as it's left alone. My biggest
concern, by far, would be transitions between K&T and newer wiring.
3) Pool sweeper issues are most likely coincidence.
4) Fixing things after a DIY'r has f'd it up is tedious.
5) I have to get another beer.
P&L
K&T wiring usually shares a neutral for all circuits too ...
Not the source of his problem though, as you said earlier.

Sounds like a ground bond issue to me too
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