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marigolds
Gainfully employed, finally
Premium,MVM
join:2002-05-13
Saint Louis, MO
kudos:2

Unexpected voltage on circuit


The Circuit
I have a two wire (no ground) romex coming from the ceiling into the back wall of our storage room where it terminated at a light.
This wire in is represented by the two arrows coming from the top of the page.

I removed the light and ran 2 wire + ground down to a new receptacle below where the light was. Wired the ground up to the receptacle , but left it unconnected and capped in the light box. This way the ground wire is there if I am ever able to run ground to the light box.

That worked fine with no issues.

Next, I ran pigtails off the neutral and hot in the light box. This is represented by the two wires going off to the right from the two upper left wire nuts.

I put a 2-gang frame on top of the box and mounted two receptacles (to eventually plug in utility lighting).

The neutral pigtail I split and ran to each of the receptacle neutrals.

The hot pigtail I ran out to a switch loop via 2-wire + ground, with the hot labeled neutral off the switch coming back into the box, where I split to the hot on each of the receptacles.

Finally, I connected the ground on the switch to the ground off the original lower receptacle and connected all of that to the ground on the two upper receptacles

The circuit behaves as expected (switch turns on both upper receptacles while lower receptacle is always hot). All three receptacles are currently open ground (have them labeled as such and working on finding location to place upstream GFCI on entire circuit), which is what I would expect.

The problem is that, with the switch off, the three-prong tester is lighting up dim on the middle light in the upper receptacles. A continuity tester picks up nothing between any of the three holes when the switch is off. I will try to go at this with a voltimeter later today. (What should I test with it?)

Why would this be happening? Am I just picking up phantom voltage from the run going through the box down to the lower hot receptacle?
Is this because I wired the two gang in parallel and should wire them serial?
Am I somehow getting voltage relayed along the ground wire that is only hooked between the switch and the three receptacles?

Have I done something wrong in my wiring arrangement?
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nunya
LXI 483
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join:2000-12-23
O Fallon, MO
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Current is inducing on the unterminated ground wire. You should run a ground before energizing this circuit. Especially if you plan on plugging in fluorescent shop lights to the switched receptacles.

It's never OK to install a grounded receptacle without an actual ground or GFCI in front of it. Even temporarily.
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garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
reply to marigolds
said by marigolds:

Finally, I connected the ground on the switch to the ground off the original lower receptacle and connected all of that to the ground on the two upper receptacles.

So, the outlet grounds are all connected together, and then to the switch ground, and then... ?

Assuming nothing, yeah, you have induced voltage in the ground wire, but you should NOT use a three prong receptacle there as nunya said. Why would you do that?


marigolds
Gainfully employed, finally
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join:2002-05-13
Saint Louis, MO
kudos:2
said by garys_2k:

said by marigolds:

Finally, I connected the ground on the switch to the ground off the original lower receptacle and connected all of that to the ground on the two upper receptacles.

So, the outlet grounds are all connected together, and then to the switch ground, and then... ?

Assuming nothing, yeah, you have induced voltage in the ground wire, but you should NOT use a three prong receptacle there as nunya said. Why would you do that?

Because there are no grounds whatsoever in half the house. We have no idea why.
The circuit is disconnected at this time I'll be looking for that GFCI.
Should I just disconnect all those grounds wires and leave them unconnected in the walls then? Use GFCI with no equipment ground until the day comes I can get a ground over to that wall?
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marigolds
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join:2002-05-13
Saint Louis, MO
kudos:2
reply to marigolds
Here's a thought. If I ran hot to one of the upper receptacles first and made that a GFCI, then ran off the load terminals of the GFCI to the lower receptacle and ran the load hot to the switch and load neutral to the neutral on the other receptacle, that would GFCI protect all three outlets, right?

iknow
Premium
join:2012-03-25
reply to marigolds
the problem you'll have is you won't be able to use anything with a grounding plug on those outlets, OR fluorescent lights. it won't be safe. either fix the grounds properly, or use 2 blade receptacles, and don't wire any fluorescents to that circuit. only use devices that don't need a ground, like double insulated tools etc. it's better to have proper grounds though.


marigolds
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Saint Louis, MO
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Grounds are not going to be that feasible. I already tried to get quotes from six different companies companies and they all rejected the job.
(Slab house, 3' of blown in insulation, brick walls)

But wait a sec here, I thought you could use grounded plugs in a GFCI protected outlet labeled "No Equipment Ground", you just are not going to have any ground protection for the equipment that you are plugging in to those plugs.

We have ungrounded hardwired light fixtures all over the house. We cannot use florescent in those?
(Incidentally, these outlets will be supporting undershelf LED and nothing else.)
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John Galt
Forward, March
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Happy Camp
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Some florescent lights require an actual ground wire to operate...

How old are the existing ones?


nunya
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O Fallon, MO
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reply to marigolds

But wait a sec here, I thought you could use grounded plugs in a GFCI protected outlet labeled "No Equipment Ground", you just are not going to have any ground protection for the equipment that you are plugging in to those plugs.


That cheat comes with caveats. The GFCI is there for protecting people, but will not necessarily protect the equipment plugged in. Some devices and appliances require a "real" ground to function properly. I mentioned the cheapo shop lights: Many people run out and get these, a ground cheater plug, and a socket / outlet converter. They are then baffled when their lights don't work properly, work intermittently, or have trouble starting - many of them need a ground.
This is just one example of many devices that require a real ground.
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marigolds
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Saint Louis, MO
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1 edit
reply to John Galt
said by John Galt:

Some florescent lights require an actual ground wire to operate...

How old are the existing ones?

These are all compact florescent bulbs, put in place in the last 3 years. I cannot think of anywhere in the house that has tube florescents any more. The only two receptacles in the house with sensitive electronics are grounded (as is the kitchen). We thought for sure the grounds were added later because of the locations, but were informed that the locations that are grounded and the vintage of the wire indicate that the house was almost certainly built with just a handful of locations grounded (1964).

(And what is there now is certainly better than what was there before. A third receptacle 2-prong extension cord end piece stick out of the wall where it was hard wired into the ungrounded circuit off the back of the existing light with no box.)

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
Yes, CFLs will operate fine without a real ground, some of the cheapie tube fixtures needed a real ground to encourage the starting arc to fire. No ground, no start.

Using the GFCI outlet will keep you safe, that's the most important thing in the end. Put it in the "first" location, however that's wired, and every downstream outlet must connect to its load hot and neutral connections. The supply hot and neutral should not go to any of the protected outlets, use only the GFCI's load terminals for that.

iknow
Premium
join:2012-03-25
reply to marigolds
you may find some equipment with a grounding plug that works fine in a normal grounded outlet, but has too much leakage to ground to operate on a 2 wire GFCI. it would keep on tripping it.


Jack_in_VA
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North, VA
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said by iknow:

you may find some equipment with a grounding plug that works fine in a normal grounded outlet, but has too much leakage to ground to operate on a 2 wire GFCI. it would keep on tripping it.

There should be "0" current to ground on any equipment. If there is ground current present especially enough to trip a GFCI then the equipment is defective.

iknow
Premium
join:2012-03-25

1 recommendation

said by Jack_in_VA:

said by iknow:

you may find some equipment with a grounding plug that works fine in a normal grounded outlet, but has too much leakage to ground to operate on a 2 wire GFCI. it would keep on tripping it.

There should be "0" current to ground on any equipment. If there is ground current present especially enough to trip a GFCI then the equipment is defective.

R.F supression capacitors, humidity, and capacitance between the wires and case can cause that. measure the current on a ground on equipment that has a 3 wire plug sometime.


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to marigolds
said by marigolds:

The problem is that, with the switch off, the three-prong tester is lighting up dim on the middle light in the upper receptacles.
[...]
Why would this be happening? Am I just picking up phantom voltage from the run going through the box down to the lower hot receptacle?

You are picking up voltage induced between the wires. Those neon bulbs are *extremely* sensitive, only takes a tiny current to make them glow. If you connect one leg of a bulb to a hot wire it's enough to get your hand close to the other wire to make it glow.


marigolds
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Saint Louis, MO
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reply to marigolds
So overall, the dim tester light is not a problem.

My problem is that I need to get my inline GFCI protection in place before I use the circuit (which I already knew), and hopefully someday figure out a way to ground it.

Thanks everyone for your input!
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Jack_in_VA
Premium
join:2007-11-26
North, VA
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reply to iknow
Just did. Result was "O"


SparkChaser
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Downingtown, PA
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1 recommendation

said by Jack_in_VA:

Just did. Result was "O"

It's going to depend on the equipment in use. Coming out of my UPS is 1.5 ma.


cowboyro
Premium
join:2000-10-11
Shelton, CT

1 recommendation

reply to Jack_in_VA
said by Jack_in_VA:

There should be "0" current to ground on any equipment. If there is ground current present especially enough to trip a GFCI then the equipment is defective.

False.
Some devices have capacitors from both lines to ground. 4.7nF is a common value in switching supplies. That's enough for a 0.2mA current to start with...


Jack_in_VA
Premium
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North, VA
kudos:1
Reviews:
·Millenicom
The neutral and ground should be the same potential as they are connected together in the panel so how do you figure "current" flow? You could lift the ground in the panel and the device most likely would never know it. That would however stop your current flow.

Good grief there are probably millions of homes that the wiring is old enough not to even have grounds. How are they functioning?


whizkid3
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join:2002-02-21
Queens, NY
kudos:9

1 recommendation

reply to Jack_in_VA
said by Jack_in_VA:

There should be "0" current to ground on any equipment. If there is ground current present especially enough to trip a GFCI then the equipment is defective.

Many equipment have line filters that shunt EMI to ground. Anything with a grounded chassis (everything), theoretically shunts any received or produced electrical noise to ground. Surge suppressors shunt transients to ground. While this current may not add up to a whole lot; it is certainly not zero and does not mean the equipment is broken. Current from electromagnetic induction, where for example, the ground wire runs in parallel for some distance with the equipment wires, will produce ground current. On the other hand, with burnt motor windings and similar other issues that produce leakage current; current on the ground can in fact indicate their is an problem with the equipment. The answer is - it all depends.

On the other hand, it makes no sense to plug this equipment into a GFCI for personal protection. The GFCI can in fact trip and although doing its job, would have to be considered a nuisance trip, IMHO.

I have measured a few amps of leakage current in computer rooms, simply from induction and EMI leakage current coming from the servers. The owner was concerned and the issue was investigated very carefully. The end result is that it was simply the sum of all leakage current from line filters and surge suppressors in the power strips and servers.


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to Jack_in_VA
said by Jack_in_VA:

The neutral and ground should be the same potential as they are connected together in the panel so how do you figure "current" flow? You could lift the ground in the panel and the device most likely would never know it. That would however stop your current flow.

Good grief there are probably millions of homes that the wiring is old enough not to even have grounds. How are they functioning?

I am talking about your assertion that
said by Jack_in_VA:

There should be "0" current to ground on any equipment.

Current to ground can flow without having a malfunction.
Yes, you can disconnect the bonding and the device wouldn't care, however the ground line would be floating at ~60V

robbin
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join:2000-09-21
Leander, TX
kudos:1
reply to marigolds
said by marigolds:

So overall, the dim tester light is not a problem.

My problem is that I need to get my inline GFCI protection in place before I use the circuit (which I already knew), and hopefully someday figure out a way to ground it.

Thanks everyone for your input!

Yes, put in a GFCI and then if you have problems you can deal with them.