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 Post subject: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 5:49 am 
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I have a 40 watt equivalent LED that stays on (at about 1/10 output) even when the power switch is off, and even when the breaker to that circuit is shut off. 24/7 it runs, so I don't need a night lite.

I understand how there could be RF, but I'm not near any kind of radio tower. And - it's only one LED, out of the ones I have (quite a few now). What would be likely scenario to explain? Is this common?


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 5:52 am 
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Maybe some kind of common-mode voltage? I guess that's easy enough to check.


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 9:43 am 
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Location: San Jose CA
you probably have a motion sensing, occupancy sensing or timer switch attached to the fixture. You can either change the switch to one that does not need as much (or any) thru current to operate or change the bulb to non dimmable type. It still might flash periodically.

Problem is that many automatic switches especially older ones took advantage of the fact that the bulb itself provided a path to neutral (white wire) in order to maintain 2 wire compatibility with manual switches for easy upgrade. For incandescent, this leakage current was not enough to light a bulb, maybe 10mA. But for LED it is apparently enough current to excite the integrated switching power supply in the bulb and get it to light. Newer automatic switches have 3 wire hookup avoid using line current through the bulb.

I had to try several bulbs and occupancy switches before I had one that did not flash once every few seconds in one instance.

High RF energy might light the phosphor in a florescent bulb but not an LED.

I almost missed the part about the breaker. Is it a split breaker? (2 switches in one slot) or are you maybe treating a GFCI trip as a breaker?


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 10:17 am 
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Hello haklesup,

Thanks for the reply. Yes, it's a split breaker. The fixture that holds the LED is very old - from the late eighties. It's just a basic ceiling light. It's been on, night and day, for the three weeks since we twisted it into the socket. Today, I went to look for mysterious voltages, and found zero (using my DM and also the DM+RF probe). Also, the light was not lit.

Scratching my head. It did rain last night.

Edit: it is NOT a split breaker. That was the one above it.


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 1:14 pm 
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Location: Mideast USA
Hi.
It is a behavior reported many times in several forums. Experienced myself on a hallway LED bulb, faintly on when should not. My bed headboard LED lamp has the same behavior when off.

From digesting what could be the causes from many reports, my suspicion is the faint current comes from capacitive leakage in mostly 'romex' type of wiring were conductors run closely paralleled forming a capacitor.
Now, how an OFF / open switch (as in my headboard lamp) leaks capacitively; I still scratch my head.

No GFCIs in my home, no RF transmitters, and most of equipment is kept unplugged when not in use. No Wifi, not even a single dimmer, no weirdness.

Ronald : Is it in a 'three way' circuit ? If you swap another LED in that location, does it also faintly glow ?

----> https://duckduckgo.com/?q=faint+led+glo ... cal&ia=web



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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 14, 2017 6:11 pm 
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Hmmmm.............. :?

It sounds like a case of "Stray Voltage".
From Wikipedia: https://en.wikipedia.org/wiki/Stray_vol ... conductors

With power off to the socket.
Put your DMM(Digital Multi Meter) on AC Volts.
Put your test leads on the inside & outside contacts that the bulb would make contact with it.
Image
If your reading 10Vac or higher.
Then you either have a bad Light Switch, or the wiring going to the socket is wired backward,
or the wiring in general is breaking down.

Normally this won't effect florescent bulbs (CFL's) or incandesent bulbs,
since they require more current to get them to glow.

But bad wiring is a Fire Hazard. So, get it checked out!


Signed: Janitor Tzap


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 Post subject: Re: LED stays on 24/7
PostPosted: Tue Aug 15, 2017 11:35 am 
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Location: San Jose CA
Are you saying that after you took the bulb out and tested the voltage, it was not lit when you put it back in. Time to take the fixture out and inspect the connections for polarity.

Rather than using a DMM, use a non contact AC voltage probe. then you can check each wire independently and verify only black is the hot lead. Alsop get a wiring tester and verify hot and neutral are not reversed. If you had hot (swapped) on neutral and a short to ground, it might light and might not trip a breaker.

What kind of switch, is it just a plain old SPST wall toggle? Are you sure you are toggling the right breaker, I mean if it remains on, that implies the breaker is bad or you tried the wrong one. And you have swapped an incandescent in and it works predictably?


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 Post subject: Re: LED stays on 24/7
PostPosted: Tue Aug 15, 2017 2:27 pm 
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haklesup wrote:
Are you saying that after you took the bulb out and tested the voltage, it was not lit when you put it back in. Time to take the fixture out and inspect the connections for polarity.

Rather than using a DMM, use a non contact AC voltage probe. then you can check each wire independently and verify only black is the hot lead. Alsop get a wiring tester and verify hot and neutral are not reversed. If you had hot (swapped) on neutral and a short to ground, it might light and might not trip a breaker.

What kind of switch, is it just a plain old SPST wall toggle? Are you sure you are toggling the right breaker, I mean if it remains on, that implies the breaker is bad or you tried the wrong one. And you have swapped an incandescent in and it works predictably?


I could tell the LED was not lit before I removed the glass fixture cover bowl. Today, I used my DM, and measured between the center conductor of the bulb socket to a close-by metal pipe. Voltage was 119VAC. Then, measured the outside (neutral) part of the socket, and it was zero (on the high scale). Voltage was zero on center conductor when switch was turned off. So, the wiring is not reversed. Incandescent bulb works fine (no glow when off though).

I'm wondering if I have some ground loop voltage. That's why I mentioned the rain.


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 Post subject: Re: LED stays on 24/7
PostPosted: Tue Aug 15, 2017 2:36 pm 
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Janitor Tzap wrote:
Hmmmm.............. :?

It sounds like a case of "Stray Voltage".
From Wikipedia: https://en.wikipedia.org/wiki/Stray_vol ... conductors
...
With power off to the socket. Put your DMM(Digital Multi Meter) on AC Volts. Put your test leads on the inside & outside contacts that the bulb would make contact with it ...
...
Signed: Janitor Tzap


Hello Tzap:

I'm currently getting zero voltage across the light socket when the switch is turned off. I'm beginning to think I've got a ground loop problem of some sort ... (see my post to haklesup)

Hello Externet:

Quote:
"No GFCIs in my home, no RF transmitters, and most of equipment is kept unplugged when not in use. No Wifi, not even a single dimmer, no weirdness."


I have GFCIs, but not on this circuit. Guess I'll have to wait for the ground to dry, and try your suggestion.

- Ron


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 Post subject: Re: LED stays on 24/7
PostPosted: Thu Aug 17, 2017 9:54 am 
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Location: San Jose CA
still wondering what kind of switch behind that bulb?


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 Post subject: Re: LED stays on 24/7
PostPosted: Thu Aug 17, 2017 10:06 am 
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haklesup wrote:
still wondering what kind of switch behind that bulb?


It's just a plain old SPST wall switch. I took it out and looked at it, put the continuity tester on it, worked it a bunch. Absolutely nothing wrong with it AFAICT. Light is still off today.

- Ron


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 Post subject: Re: LED stays on 24/7
PostPosted: Fri Aug 18, 2017 12:43 am 
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Now let's recap a bit and put it together...
Some of these are interrelated so they are not in a logical order, but here are some points to ponder.

Unless you live near Roswell NM, the LED must be getting power from someplace. I doubt that, unless you are next to a big transmitting antenna, you will light the LED. A CFL is more likely to light than a LED.

You say that the LED is still dim when the branch circuit breaker is off. Have you tried other branch breakers, or the main breaker? What happens? Take the wire off the branch breaker and check for any voltage to ground. There should be none. Check the removed wire for voltage to ground, there should be none. Checking the wire resistance to ground is useless unless you are absolutely sure there are no loads still connected, If there are, you will read through the load to neutral and to ground,
Ground the wire removed from the breaker Is the LED still dim or is it off?

If you find any voltage, consider that the Sparky that wired the house may have used some illogical scheme to connect the circuits. In some older houses ceiling lights were often connected to other ceiling lights or outlets. Something may be amiss with a device in another room and that may be the problem.
Maybe the circuit is connected with outside wiring that may be damp and causing leakage. GFCI’s are a good place to be suspicious since they are often mixed in a box with non GFCI circuits.

You said no dimmers or occupancy sensors are in the circuit, but if there are, they cannot reliably be tested with a voltmeter. The Triac inside these devices need some current to conduct and most digital meters will not load it properly. Solid state relays even caution against testing without a load! Even when the dimmer or sensor is ‘Off’, there is usually some small current through the turned of triac junction unless the device also has a metallic switch in the line.

The AC Polarity on the socket, although correct, is probably irrelevant anyway unless s there are cross connections to other circuits.

Is this a home run circuit of NM cable, or is it grouped with others (looking for induction/capacitance)
Possibly a conduit installation is involved which are notorious for ‘stray’ voltages with a high impedance meter.

Anecdotal Notes:
Once ran into a situation where the duplex outlets were split and fed from two different breakers. Fortunately they were on the same phase since the blacks were interconnected. It was a big mess.

Years ago I troubleshot a tripped breaker that supplied ceiling lights in three upstairs rooms. After several lights were dropped and boxes checked I wound up back in the basement and found a shorted sump pump. I guess the theory was black and white, all the same, just hook them up!

There was an outside overhead porch light and an Inside ceiling foyer light. There were two SPST switches on the same plate. Switch 1 turned all lights off. Switch 2 turned off the outside light and that made the inside light get brighter. No big puzzle. Switch 1 was in the power feed line to the inside and outside light, which were in series to neutral. Switch 2 paralleled the outside light. Seems this was a somewhat common wartime trick to save energy. You had dim lights inside and out when you come home. Flick switch 2 and the outside light was off and the inside light was bright. Flicked switch 1 and both were off. Trace that out and try to fix it with all separate wires in a knob and tube system!

Worse case…..move!



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 Post subject: Re: LED stays on 24/7
PostPosted: Sat Aug 19, 2017 5:25 am 
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Lenp wrote:
Now let's recap a bit and put it together...

Worse case…..move!


Hi Lenp:

Thanks for the detailed prescription. You know, I've suspected that the wiring guys may have had some newbie help, based on some things I've found. Some of the outlets were "upside down" - others not. Fixed now.

The low light level hasn't come back yet. Will do some of the checks you suggested ...


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 21, 2017 7:34 am 

Joined: Mon Aug 07, 2017 5:46 am
Posts: 8
Some of your outlets are upside down? Wow, that's crazy


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 Post subject: Re: LED stays on 24/7
PostPosted: Mon Aug 21, 2017 8:55 am 
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Location: San Jose CA
I don't think electrical code defines what is up for a wall plug. I like the ground prong on top.


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