# Voltage drop under load on A leg/voltage rise on B leg



## Fowlerfellow (Jun 2, 2011)

I'm working on an old mobile home with a 120/240v service. When the 120v microwave is energized, the line voltage on that leg drops from 120v to 110v. On the other leg, the voltage rises to 130v both at the panel and on other circuits. The main breaker is on a pole outside about 15 feet away. In that panel, which is the first point of disconnect after the meter, the neutral and ground are bonded. The pole is grounded, and the trailer has a ground as well. The neutrals and grounds were all tied together in the panel in the trailer but I separated the neutrals to the neutral bar and tied all the grounds to the wire coming from the grounding electrode.

First question -- what accounts for the voltage rise and voltage drop? 

Second question -- when an Air Popper is run on the same circuit as the microwave, the voltage drops further to 103v, what is causing this problem? How do I fix it?


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## Roger123 (Sep 23, 2007)

Sounds like an open neutral. Start out by first checking the point of connection from the power company.


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## Landmark (Mar 7, 2010)

I would guess you should check the neutral connections at the panel and as far back to the service as you can.


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## Fowlerfellow (Jun 2, 2011)

I'll go through and check all the connections. One thing I forgot to mention, with the main breaker off and all the neutrals landed and grounds separated, the bare ground coming up out of the floor (it's an OLD trailer with a shabby electrical install) sparks when rubbed against the edge of the hole it passes through. 

This makes me assume the ground is still being used as a neutral somewhere, but it's not in the panel.


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## Roger123 (Sep 23, 2007)

Fowlerfellow said:


> I'll go through and check all the connections. One thing I forgot to mention, with the main breaker off and all the neutrals landed and grounds separated, the bare ground coming up out of the floor (it's an OLD trailer with a shabby electrical install) sparks when rubbed against the edge of the hole it passes through.
> 
> This makes me assume the ground is still being used as a neutral somewhere, but it's not in the panel.


If the main breaker is opened at the pole and there is still current on the GEC then the source of this current is likely to be from another location.


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## CraigV (May 12, 2011)

Fowlerfellow said:


> The neutrals and grounds were all tied together in the panel in the trailer but I separated the neutrals to the neutral bar *and tied all the grounds to the wire coming from the grounding electrode*.


The original problem is a missing neutral. But I also want to address the bolded statement above.

Did you tie to the GE only, or also to the grounding conductor from the service equipment at the pole disconnect? The feeder should be 4-wire, not 3, as the pole disconnect is Service Equipment, and the trailer's panel is Equipment.

Also, did you remove any bonding screw from the neutral bus to the panel box?

Is there a separate ground bus? "Tied all the grounds" sounds like "no" to this.


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## Fowlerfellow (Jun 2, 2011)

I removed the load side neutral at the pole and cleaned it and put noalox on it, tightened the lug, and then checked the problem. Still no change. There is an open air splice under the trailer in the crawl space. Both legs and the neutral are spliced using split bolts and they are heavily corroded. Could that corroded splice the the source of the problem? Regardless, I will fix that tomorrow.


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## CraigV (May 12, 2011)

Fowlerfellow said:


> *with the main breaker* off and all the neutrals landed and grounds separated, the bare ground coming up out of the floor (it's an OLD trailer with a shabby electrical install) sparks


Is this a main breaker in the trailer? Or the pole disconnect switch/breaker?


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## CraigV (May 12, 2011)

Fowlerfellow said:


> I removed the load side neutral at the pole and cleaned it and put noalox on it, tightened the lug, and then checked the problem. Still no change. There is an open air splice under the trailer in the crawl space. Both legs and the neutral are spliced using split bolts and they are heavily corroded. Could that corroded splice the the source of the problem? Regardless, I will fix that tomorrow.


 
Did you meter from legs to neutral before and after the splice? With no loads you would see 120v to neutral before a break or bad connection, and considerably less after it. Yes, a badly corroded connection can definitely cause enough resistance to render the neutral useless.


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## Fowlerfellow (Jun 2, 2011)

CraigV said:


> The original problem is a missing neutral. But I also want to address the bolded statement above.
> 
> Did you tie to the GE only, or also to the grounding conductor from the service equipment at the pole/meter? The feeder should be 4-wire, not 3, as the pole/meter is Service Equipment, and the trailer's panel is Equipment.
> 
> ...


It is a three wire triplex from the pole to the trailer. In the trailer, I tied the neutrals to the neutral on the triplex providing continuity back to the pole. As for the grounds, in the trailer panel I have brought all the grounds to grounding electrode that exits the panel and runs directly down to a ground rod. This ground rod is completely separate from the pole. Did that answer your question? After I got my Joirneyman's license, I went back to college and now Im back in the trade for the summer so some of my terminology is probably off.


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## CraigV (May 12, 2011)

Fowlerfellow said:


> It is a three wire triplex from the pole to the trailer. In the trailer, I tied the neutrals to the neutral on the triplex providing continuity back to the pole. As for the grounds, in the trailer panel I have brought all the grounds to grounding electrode that exits the panel and runs directly down to a ground rod. This ground rod is completely separate from the pole. Did that answer your question? After I got my Joirneyman's license, I went back to college and now Im back in the trade for the summer so some of my terminology is probably off.


Yep, that answered it. 

The triplex is wrong for this use. There is no grounding conductor back to the service, and the grounds connected to the electrode under the trailer is of limited value in clearing faults. 

The only way to make this right, especially considering the sh !tty condition you described of the air spliced feeders, is to replace that triplex with quadplex. Assuming a 100a service, there's commonly available quad that's even called "mobile home feeder" and it's even available at some big box's. It's 2-2-4-6, direct-buriable with no jacket. About 2 bucks a foot, so there's little excuse other than labor time to dig the trench not to replace and have it right.


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## Fowlerfellow (Jun 2, 2011)

CraigV said:


> Is this a main breaker in the trailer? Or the pole disconnect switch/breaker?


Main breaker is on the pole. No disconnect inside the house. Also, the neutral bus is electrically isolated on the panel in the trailer, I did check that. 

No ground bar in the panel. The GE was originally under a lug on the neutral bus. 

Before the splice L1-N is 122.3v and L2-N 122v. After the splice, same.


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## CraigV (May 12, 2011)

Fowlerfellow said:


> Main breaker is on the pole. No disconnect inside the house. Also, the neutral bus is electrically isolated on the panel in the trailer, I did check that.
> 
> No ground bar in the panel. The GE was originally under a lug on the neutral bus.
> 
> Before the splice L1-N is 122.3v and L2-N 122v. After the splice, same.


Then the break in the neutral is after that splice. Since you read voltage to the neutral, the neutral is connected there. Can you get test leads to the outside to test continuity between just after the splice and the panel? 


No ground bar in the panel? You need to add one. How are you splicing all the branch circuit grounds together?


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## Fowlerfellow (Jun 2, 2011)

CraigV said:


> Then the break in the neutral is after that splice. Since you read voltage to the neutral, the neutral is connected there. Can you get test leads to the outside to test continuity between just after the splice and the panel?
> 
> 
> No ground bar in the panel? You need to add one. How are you splicing all the branch circuit grounds together?


I did a temporary splice of the grounds using wire nuts. There are only 11 ground wires in the panel and the grounding electrode. Three times I spliced three grounds with a jumper going to the electrode. At the electrode I used spliced the three jumpers, two leftover grounds and the electrode with a blue wire nut. Its not the finished product. All the grounds on one side of the box were hacked off to about 6" long and tied with the neutrals. All of that mess was spliced to a #6 wire that went around to the neutral bar. Needless to say, my final product will have a proper ground bar. 

After talking to the owner, it looks like we'll be replacing all the wiring from the pole to the trailer. I think this is the ideal scenario, with one exception: the owner has some old railway signaling cable that has a steel jacket and three giant solid conductors that are heavily insulated inside. He is wanting to tape a copper ground to the railway cable and use that as the new wiring.


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## CraigV (May 12, 2011)

Fowlerfellow said:


> I did a temporary splice of the grounds using wire nuts. There are only 11 ground wires in the panel and the grounding electrode. Three times I spliced three grounds with a jumper going to the electrode. At the electrode I used spliced the three jumpers, two leftover grounds and the electrode with a blue wire nut. Its not the finished product. All the grounds on one side of the box were hacked off to about 6" long and tied with the neutrals. All of that mess was spliced to a #6 wire that went around to the neutral bar. Needless to say, my final product will have a proper ground bar.
> 
> After talking to the owner, it looks like we'll be replacing all the wiring from the pole to the trailer. I think this is the ideal scenario, with one exception: the owner has some old railway signaling cable that has a steel jacket and three giant solid conductors that are heavily insulated inside. He is wanting to tape a copper ground to the railway cable and use that as the new wiring.


Please don't agree to that. Figure out what it'll cost to do the job right. Whatever that is, triple it and give him that as your price to [email protected]#k it up royaly with rr cable. If he agrees to it anyway, still refuse the work. 

I'm assuming there's no ahj/inspection in this burgh?


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## CraigV (May 12, 2011)

Actually....better idea. Scrap the RR cable for copper and steel. You can probably buy the guy a new mobile home with the proceeds. Or maybe get some quad with it and have enough left for a case of PBR.


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## 3xdad (Jan 25, 2011)

"Three giant SOLID conductors"...will be a bitter pill for many reasons.

IMO, leaving the branch circuit equipment grounds and neutrals bonded together on a three wire feeder would be better than isolating without a 4th wire. Since you separated them, you need to deal with the 3 wire and bond issue at range and dryer as well as replace feeder.

Protect your license. Use 550.33. Don't let HO tell you what to use.


Let us know what you end up doing. thanks


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## CraigV (May 12, 2011)

3xdad said:


> "Three giant SOLID conductors"...will be a bitter pill for many reasons.


I'm imagining the HO shaving it down with a shoe rasp to fit the lugs....


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## Brianrayl (Oct 4, 2013)

Fowlerfellow said:


> I'm working on an old mobile home with a 120/240v service. When the 120v microwave is energized, the line voltage on that leg drops from 120v to 110v. On the other leg, the voltage rises to 130v both at the panel and on other circuits. The main breaker is on a pole outside about 15 feet away. In that panel, which is the first point of disconnect after the meter, the neutral and ground are bonded. The pole is grounded, and the trailer has a ground as well. The neutrals and grounds were all tied together in the panel in the trailer but I separated the neutrals to the neutral bar and tied all the grounds to the wire coming from the grounding electrode.
> 
> First question -- what accounts for the voltage rise and voltage drop?
> 
> Second question -- when an Air Popper is run on the same circuit as the microwave, the voltage drops further to 103v, what is causing this problem? How do I fix it?


The power poles are dirt. Start there. If you are in a park chances are the Maintenance guy or girl has messed with hookups, trying to cheat the meter reader.


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## Kevin (Feb 14, 2017)

Brianrayl said:


> The power poles are dirt. Start there. If you are in a park chances are the Maintenance guy or girl has messed with hookups, trying to cheat the meter reader.


If OP hasn't been able to fix it in nine years, I'm pretty sure someone else has.

I'm closing this thread.


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