Ok, I need a lesson in electrical theory. HO wants me to sleuth why a lamppost about 25 feet from the house no longer works. I test the switch for positive continuity, I ensure 120v is coming into the switch box, I then go to the fixture and I read 86v over 12/2 wire. Pretty interesting. I findthe wire in the basement coming from the switchbox and follow it. It is 12/2 Romex, not UF cable. I follow it outside to where it goes above ground under a porch for about 12 feet. It then turns to go into the ground. Again it is Romex, not UF. It does not appear to go into conduit, it appears someone direct buried it for 25 feet until it goes into the fixture. Wire has been buried for 20+years and apparently worked until about a year ago when the fixture stopped working.
I reason the following: Since it is romenx, time has degraded the outer insulation and likely conductor insulation. I suspect a small part of the hot wire is exposed to the ground and leaking voltage to the ground but not enough to cause any problems at the panel box. Have I made a reasonable deduction as to the cause, or is there something else I can investigate?
Replies
ww,
Are you checking the wire at the fixture where it actually enters the post or up at the lamp socket ? Does the post have a photocell to turn the lamp on at dark ? The photocell on mine went bad and would pass some voltage, but not enough.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
No photocell. I checked the supply wires under the wire nut. In other words, disconnected them from the fixture and read the true Line voltage.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I think even non UF is good for 600V. The only issue I ever had was an ele. fence at a gate..I ran romex underground at 20KV..it didn't work well.
Like Mr.Bill said, mebbe a bad photocell?
Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"
try cutting the old splices off at the post, expose some fresh copper, and check your voltage again
just DON"T FORGET TO TURN THINGS OFF FIRST !!!
.
.
.
, wer ist jetzt der Idiot ?
No. What you have is phantom voltage ( http://en.wikipedia.org/wiki/Phantom_voltage ). If there were enough leakage of hot to neutral/ground to 86 the voltage the fuse/breaker would blow.
But if it's not UF and not in conduit, don't fix it without replacing the cable or you open yourself up to a bunch of liability.
I wouldn't fix the old cable if you paid me to. I told the HO my suspicion and said I was not really sure that was the problem, only logical. If I'm getting phantom voltage as one poster said then it's even more crazier because I only get 86v when the switch is on and 0v when off, and I do have true power coming into the switch at 120v. And I have 120v coming off right at the switch.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I'm guessing you just measured hot to neutral, not hot to ground. Sounds to me like a bad neutral connection, though it's slightly likely that it's just a corroded hot connection somewhere.Note that, since this isn't UF, it's possible that the wire has been damaged by a sharp rock, someone digging, or a rodent.In any event, if you completely replace the wire and redo the connections then the problem should go away.
If your view never changes you're following the wrong leader
And get yourself a wiggy -- they're cheap.
If your view never changes you're following the wrong leader
you have a splice that is bad.... might be in the ground or a buried J-box full of ####either way he needs a new cable run.
.
.
., wer ist jetzt der Idiot ?
Oh I meant to say also that I told the HO to fix it and do it right requires just running UF 18" below ground adn that I'd put it in conduit just the same and abandon the old.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
DanI hadn't though of wiki as a source of tech info on electical - that one article seems pretty good.How would you rate the electrical info there, generally?
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
Fair. That article in particular has trouble because someone with only primitive understanding of electricity keeps trying to "correct" it. (I think maybe they have an environmental axe to grind.) Lots of other articles are exceedingly well-written and comprehensive, though.
If your view never changes you're following the wrong leader
yep! you're right.
.
.
., wer ist jetzt der Idiot ?
"I then go to the fixture and I read 86v over 12/2 wire."
-Between hot and neutral?
-What voltage do you get from hot to ground? 20-year old Romex should have a ground wire.
Voltage loss is caused by increased resistance/impedance, usually due to a partially broken wire or a loose or corroded connection somewhere (line loss from resistance in the wire too, but not in 25 feet).
If you get the same low voltage reading hot-to-neutral as hot-to-ground, then wire damage or a poor connection somewhere on the hot seems likely. If low voltage only shows on hot-to-neutral, then the neutral has wire damage or a bad connection somewhere.
DanH has a good point, though. If you repair the connections and knowingly leave improper cable for underground use, you may leave yourself open to litigation down the road.
I'm with Dan on this..........the 86V is likely a red herring due to a high-impedance digital meter. I recommend you check it out with a cheap analog multi-meter before you do anything else.
Ed
You say you checked to see that 120 v is going into the switch box...how about the voltage at the output of the switch?? While there are other possibilities, a bad switch will cause your symtoms.
My guess, the paper in the romex is saturated alowing voltage to leak to the ground.
Voltage doesn't "leak", current leaks. If there were that much current leaking then the breaker would pop.
If your view never changes you're following the wrong leader
Your assuming the fault is allowing enough amperage to pass through it to trip the breaker, it may not be. Sometimes a connection will alow the proper voltage to pass but not enough amperage to pull the load, happen's on a pump pressure switch when a layer of corrosion covers the points. I've heard it called "showing a path".
In order for it to be as you describe there would have to be a double fault -- a bad connection plus a short. Possible but unlikely. A simple weak connection would still register 120V unloaded -- you need a partial short as well to create a voltage divider and get 86V.
If your view never changes you're following the wrong leader
My vote is the open neutral. But there should be 120v hot to ground, assuming there is a ground connected.
Thats the point, the presence of moisture in the paper, a flaw in the insulation and it arcs enough to carbon up the ends at the fault so it doesn't conduct full voltage or amperage. I guess its something you might not think about if you haven't seen it.
A few voltage measurements would settle it, of course: If hot to ground is also 86V it's a partially open hot, while if 120V it's an open neutral.
In any event it's moot, since the cable needs to be replaced, and replacing the cable (plus cleaning any corrosion at the connecting points) should clear up the problem regardless.
If your view never changes you're following the wrong leader
I have 120v coming out of the switch.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Wasn't it you that had the ground problem maybe 6-12 months ago and we went over the phantom voltage problem.
However, there maybe something else going on in this case.
You did not indicate if the light was connected when you made this measurement or if you use a wiggly or similar.
If the insulation has bad spot and water gets in or there might be a splice someplace that has gotten wet.
The wire corrodes and breaks the solid connection. But leave leaves high resistance in series with the wire.
Now, if that was all that was going on and the light was hooked up will making the measurement then the light would be glowing dimmly.
Or did not have the light, but used a meter with a low resistance, such as a wiggly, you might get such a reading.
Or you might have a series reistance at that connection but also a resistance to ground. Forming a voltage divider.
Not exactly the same thing as phantom voltage, but effectively the same; ie the cable is bad and since it is not UF it needs replacing.
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Yeah, Bill, it was me about the phantom volt problem. that was back in Feb last YEAR, man :) But you're covered since you said 6 to 12 mos. I wouldn't have thought this was phantom volt though, but now I see why it could be...I'm still using the same digital multimeter :-(If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I'm not an electrician and don't mean to stick my nose into your business, but what the heck is a wiggly. Without to much verbal abuse please explain. Thanks
tester...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
A "wiggy" is a sort of voltage meter based on a solenoid that vibrates rather than a conventional meter movement. The one on the left in the picture below:
If your view never changes you're following the wrong leader
A wiggly is a trademark name, but is also used as the common name for a type of tester that used a solenoid pulling against a spring. And the spring is marked in voltage.You feel it vibrting and the marker on the spring gives a rought indication of the voltage. It is a crude measurement, but in most cases more than accurate enough to see if you have power or not.It's main advantage is that is draws enough current that it is not subject to phantom voltage.I see that I miss spelled the name. It is Wiggy. Named after the inverter Wiggington.http://www.acehardware.com/sm-square-d-wiggly-voltage-tester-vt-1--pi-1297996.htmlhttp://findarticles.com/p/articles/mi_qa3726/is_200405/ai_n9458300
.
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You can take an extenion cord with a good ground out to the lite. Check the hot on the burried wire to the ground on the cord. While the cord is there you could also jumper it to the lite to see if its OK.
the wire is damafed or a exterior connection is correded and the electricty is bleeding back to earth or not has met a high level of resistance due to corrosion
replace the feed..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Romex as in NM or UF???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Again it is Romex, not UF."
If your view never changes you're following the wrong leader
sorry..
came in late and didn't read the whole thread...
change the wire to UF..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
You didn't even read the whole post. :) But BTDT.
If your view never changes you're following the wrong leader
sure I did...
some of it just didn't sink in...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
If you have a roll of wire that you can use to test, disconnect the old wire at the switch and at the lamp socket. Connect new wire and just roll it out to the lamp socket. Before connecting to the socket, test, both hot the neutral and hot to ground. Then connect it to the socket and test. If the first test is ok, then you know it is the wire between the switch and the socket. If the second test is a problem then the socket is a problem. Maybe even both. But now you should know.