Electrical Problem

[Redoverfarm]

Today I wired up the remaining switches in the cabin.  I hooked up my generator to my circuit panel box to energize the panel box.  Everything was working fine EXCEPT I discovered something odd.  I had one recepticle that I had not installed.  The wires were seperated so there was no chance of shock.  I tested the wires with the power on and it was correct w/ 120.  Then turned the breaker off for that particular circuit and then retested the current with a meter.  No power as anticipated.  But when I checked the neutral against the copper ground I found the same 120.  I started worring and went to the panel box and tested the neutral bar with the copper wire bar and found that it also had current. 

I am assuming that maybe when I had wired either a switch or a recepticle that when pushing the switch or recepticle back into the box that the copper ground wire or neutral may be in contact with a hot lug on the switch which in turn is energizing the neutral.  Or I accidently switched a wire somewhere. 

Any thoughts?

Funny though that all the switches and recepticles are working correctly. 

[MountainDon]

Does this happen on all circuits or only that one? or two, or....  ?


Is the panel wired as a 120/240? Or is it only 120 as I did mine?

[Redoverfarm]

Does this happen on all circuits or only that one? or two, or....  ?

Don I am not sure which circuit it is.  I do know that the neutral bar and the copper ground bar in the circuit panel box is reading a voltage.  I think I can probably isolate the circuits in the panel box by shutting off each one at a time and testing the bars and see if it disappears and indicates one particular circuit.  If it does then I can go to the recepticles and switches checking them out.  PIA .If not I will have to go into every recepticle and switch to find the problem.

I will just have to dig into it tomarrow and see what I can find I guess.

Am I not correct that even with the power on there should be no current on the neutral or the copper ground wire when checked against each other.

[MountainDon]

There should be no voltage measured when you put a test meter across the neutral white and the ground wires. Unless there's a fault someplace.

If there's a misplaced wire or short someplace tripping the braker on that circuit should isolate the problem I think. If it doesn't I'd then try disconnecting the neutral wire at the panel or each circuit, one at a time until the ault disappears. That should be easier than pulling each and every switch and receptacle.

[MountainDon]

Do you have one of these?

Gardner Bender "Sure Wire" Branch Circuit Analyzer



http://www.lowes.com/lowes/lkn?action=productDetail&productId=12370-1781-GRT-800&lpage=none

[ScottA]

I'm no electrician but if you had a hot wire shorted to the neutral wouldn't that trip the breaker? How did you wire to the generator? Is it grounded?

[MountainDon]

Generator wiring can be weird at times, with the grounding. I don't recall exactly what I'm trying to say. 

That's one reason I was asking how it was connected; 120/240 or just 120. And if it's 120 only how did you wire up the feed to the two halves? Maybe try disconnecting one half at a time and checking?

[MountainDon]

I'm no electrician but if you had a hot wire shorted to the neutral wouldn't that trip the breaker?

I think that's right, and I'm no electrician either. I'm not clear what will happen if a white and black lead were to be interchanged at a receptacle though. Somehow I don't think that will cause the breaker to trip. That would be found by the Gardner Bender tester though.

[Redoverfarm]

Don I don't have a tester as you posted.  I was using the volt meter for the recepticles.  As far as hooking the generator up to the panel box I did so with a extra breaker.  I pigtailed a male plug onto 10 ga and then wired it to the breaker and neutral bar. This energized the panel with 110/120.   I didn't have a hex big enough for the lugs on the panel.  Understand this was only temporary to check out the three way switches that I had connected up as well as recepticles.  Once I can determine that everything is correct then I will make a more permanent connection.  But that is down the road a while being that I will battery bank, inverter and standby generator. 

[MountainDon]

One of those testers could be handy as it would detect a switched white and black wire at the receptacle where the mixup occurred, as well as other faults.


That's how I ran our cabin for nearly a year, except I ran the power rom a cheap inverter running of the RV batteries some of the time. When we wanted to run the microwave I'd switch the plug from the inverter to the generator.


Q: Do you have the neutral bonded to the ground at the service panel? Some panels have separate neutral and ground bars, other are combined I think. I seem to recall that bonding be done  at the panel that contains the main breakers. Then that is connected (bonded) to the earth via a ground rod, metal water pipe, or other approved earth.


I have to admit I'm not sure what happens if you do not do that. Grabbin' at straws.   

[davidj]

I believe some generators have ground connected to neutral, some don't.  And, as Don says, boxes are the same way.  You only want ground and neutral joined at one point, which should be at the main panel.  In a simple setup, the generator is effectively the main panel.  But as things get more complicated, then you connect them at a separate breaker box and want them disconnected at the generator.

If ground and neutral aren't connected then neutral can float to any voltage.  If, for example, there's a high resistance path from live to ground (e.g. a small indicator light) and no path from live to neutral or neutral to ground, the live terminal will be at about ground voltage and neutral, which is forced to be 120V less than ground by the generator, will be at -120V (which is basically the same as 120V, given it's AC).  Once you connect ground and neutral with a big bit of copper, there's a low resistance path from ground to neutral so they'll be at the same voltage and the indicator light high resistance path becomes is irrelevant.

The fundamental issue is that a simple generator or transformer only sets the difference in voltage between the two output terminals, with no constraint on the voltages relative to anything else like local ground.  If you don't tie one end of the output to ground, normally irrelevant high-resistance connections (possibly even the meter you are using to try and work out what's happening) define the voltage relative to ground.

PS I'm not in any way an electrician - I'm not saying this is necessarily the cause, but rather an explanation of what might happen if ground and neutral aren't connected.

[MountainDon]

Thanks for that davidj.  I needed that input to shake up my brain cells.

I did a little research just now to see if I could clarify things. It seems that "most" generators that have a built in receptacle panel will likely have a neutral to ground bonding inside the generator. When that is connected to a cabin/house system that also has a neutral to ground bond, problems may occur.


Thinking back to my cabin I remember I had to break the bond in the service panel when I was using a cheap inverter to supply AC power through the service panel to the cabin from the RV batteries. With the panel bond in place the cheapy inverter would trip off. I discovered the solution through pondering the ground neutral bond and trial and error.


Now I have the panel bond properly in place and the Outback VFXM inverter grounded as per Outback's instructions. Using my portable generator with that is not a problem as this mobile model inverter includes neutral and ground switching when connected to an AC input. Others may vary.


Grounding and bonding are not the same and it's easy to be confused.   

[MountainDon]

More.... according to OHSA...

http://www.docstoc.com/docs/6828298/Grounding-Requirements-for-Portable-Generators

[Redoverfarm]

OK here is the latest.  I think I found the offending wire.  I isolated it to one circuit. In that circuit the neutral to ground reads 120 (+-).  The generator is putting out 120.  I am getting 120 to the breaker and checking the breaker wire(hot) to neutral bar it is reading 120.  I pulled the ground wire off of that circuit and I am not getting the 120 on the ground to neutral. I am however getting the 120 from that disconnected ground to the neutral bar.  I have looked at all the recepticles and switches in that circuit and can not find anything wrong.  I am at a loss.

Here is the pigtail from the generator to the panel box.



Here is a picture of the panel box.



Here is the jumper wire connected to the breaker which is engergizing the panel box.  



The jumper wire from the pigtail is attached w/black to breaker hot lug, white to neutral bar and ground to ground bar.

There is no wires connected out of sequence to the junction box, switches or recepticles, nor can I find any cut wires with the boxes.

[MountainDon]

I would try rewiring that temporary feed up to where the AC input would be connected if the feed was coming from the power company, rather that backfeeding that breaker. I don't know what difference it would make, and I don't think it should, but my mind would be more comfortable that way.


Are those two ground buss bars connected to each other? Connected thru the case/chassis?
And connected (bonded) to the neutrals?


How does the hot power get from the left side where it is backfed thru the breaker, to the right side? On my cabin panel I had to jump the left to the right as I did not have a three wire hot-neutral-hot wire coming in like from the power company here at home.

[Windpower]

Are you sure that your generator is not 120/240 volt output

the way your 'pigtail' is wired only half of the circuits  should be powered up (if you have just 120 coming in from the generator)

I would say that your set up is unsafe

I presume that the generator has a fuse or breaker --therefore the 'hot' or 'hots" from the generator need(s) to be connected to the large terminals lugs at the top of the panel -- not through a breaker, the neutral needs to be connected to the neutral lug at the top as well as the ground buss bars



any thing else is asking for a tingle (120 V) or a damn uncomfortable shock that could put you down on your butt (240 V)

Be sure that frame of the generator is connected to a solid earth ground too (several feet of copper driven into the earth near the generator)

not beating you up, I just want you be around here --I enjoy your posts

[Redoverfarm]

Windpower this was just a temporary set-up to check the switches and outlets.  Out of curosity I hit the box with a meter and that is when I discovered the problem. The pigtail is a factory one that breaks the 220/240 legs into 4-110/120 for extension cords. I just ran a temp 10 ga. from one of the 110/120 side.  Each has an individual fuse and the generator does have a breaker. Once I get the larger generator gas line ran it will be totally installed with the main lugs of the panel box. 

[davidj]

Kill and disconnect the generator, then do continuity (or resistance) checks between both neutral bars and both ground bars - all possible combinations.  They should all be connected to each other - very close to 0 ohms, or perfect continutity.  If they're not, that's part of your problem.

If you fix the neutral/ground connectivity issues, be careful when you switch it back on.  As I said before, I think the voltage on the neutral wire is due to a low current connection.  If it's a high current connect, breakers will flip as that's a short (or if they don't flip, stuff'll start smoking!).

Windpower's right - half of your circuits should be dead as it looks you're only connecting up to one side of the box (unless there's an extra connection or special breaker that's turning it into a 110V-only box).

And don't stand in the bath or use both hands when you're doing any of this - it's harder to kill yourself when it's dry and the current path isn't through your vital organs!

[Redoverfarm]

Well the problem is no longer a problem.  I found out what was wrong.  It was a common mistake.  When I had attached the T&G to the wall I mistakenly drove a finish nail into the wire.  It hit dead center and just nicked the hot & ground wire. Just enough for the nail to make contact with both thus giving me a live ground wire.  I got some good advice in reference to checking the resistance (ohm) on the hot and ground and narrowed it down to the location.  Thank goodness it was not in the log wall but the framed addition.  About 3 hours to remove the T&G wall, repair and replace the T&G.  Hopefully someone will gain some very useful information from my trouble.

Here is a picture of the wire and it's location.





BACK TO NORMAL



BTW Windpower both sides of the box are hot with just feeding the one side. Still here so I guess you will still be amused by some of my Post

Thanks to all again.

John

[MountainDon]

I'm glad you found that nail problem.  

It is a puzzle why the right side of the panel should have power with only a back feed on the left.  The two halves should be isolated. When power would be connected from a 120/240 volt source (grid or genny) one hot leg (120V) would be attached to the left and the other (120V) to the right.  At least that is how my cabin and house work.  

[davidj]

If you can connect hot to ground and not blow a breaker then something else is wrong too - it still looks like you've still got no connection between ground and neutral.  This is potentially dangerous - hot/ground shorts should trip breakers, not leave all of your exposed metal at 110V!

[bayview]

I'm no electrician but if you had a hot wire shorted to the neutral wouldn't that trip the breaker? How did you wire to the generator? Is it grounded?

   I also am surprised the breaker did not trip. . . Isn't that what a breaker does?  Trips when a "hot" grounds to neutral. . .


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[MountainDon]

Trips when a "hot" grounds to neutral. . .

John said the hot (black) was shorted to the ground (bare), not the neutral (white). "It hit dead center and just nicked the hot & ground wire. Just enough for the nail to make contact with both thus giving me a live ground wire."

If the breaker panel had the ground bonded to the neutral, that would provide the needed connection to trip the breaker, as that would provide the hot to neutral short circuit. But we've danced around the bonding issue.

If I understand things correctly this is an example of why the panel ground to neutral bonding is mandated by the NEC.

[Redoverfarm]

Just for the curious.  What got me first started was that when I pluged up the generator I did not have the ground wire plug on the generator (pigtail) to the ground buss in the panel box.  When I did so it blew the generator breaker and the circuit breaker.  That's how I knew I had a problem.  The hot ground from the panel box tripped the generator breaker.  "Now you know the rest of the story". From what I can tell everything is working correctly.  I will double check when I permanently install the other generator with the apprioate ground rod and bonding.  I still have to run conduit and wires from the generator approximately 25-30 feet to the panel box.  

But now I have a gas line.  We finished it up this evening and pressured it to 70#.  Will check in the am and see what it reads.  After 1/2 hour it had not dropped.  The guage may be lower in the am depending on how cold it gets tonight.   If it drops I will add to about 80 and check throughout the day to see a drop.  Didn't have any soap to check the joints will do that in the am.

Thanks everyone for your thoughts . suggestions and concerns.

[bayview]

Are those two ground buss bars connected to each other? Connected thru the case/chassis?
And connected (bonded) to the neutrals?

  It would be a good idea to connect those two ground bars somehow other than through the case . . .  

   Ultimately the ground and neutral are connected to each other, (somewhere)  I would still be concerned that the breaker didn't trip when "hot" grounded to the bare wire . . .

   I see your answer after I typed this . . .


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