One leg 168 volts, other is 72

[sfav8r]

This started out to be simple (don't they all). I assumed I was going to find an open neutral.

The original complaint was that the garage lights were flickering (flourescent). I measured voltage at the panel and had 168 on one leg and 72 on the other.

I checked the neutral and also ran a "jumper" frorm the grounded water pipes to the nuetral/ground at the panel...same problem persisted.

The really exciting part is that for no apparent reason, the problem disappeared. I tried for over an hour to duplicate the problem but I couldn't. I turned breakers on/off, maximized the load etc. with no luck.

As I was getting ready to leave, presto...same problem. Then it went away after about 15 minutes and I could not duplicate it again.

I am operating under the assumption that since I ran a jumper from the ground rod to the neutral, that I have eliminated a poor neutral connection from the power company as a possibility...

Any suggestions?

Thanks.

 

[stamcon]

Re: One leg 168 volts, other is 72

You have not ruled out a bad neutral. The ground rod is not connected to the PoCo transformer and will not perform the same as a proper neutral. Call the PoCo to check their connections.

 

[apauling]

Re: One leg 168 volts, other is 72

had similar experience with loose PG&E neutral, a little wind will keep everything changing. PG&E tightened lug and problem went away.

 

[sfav8r]

Re: One leg 168 volts, other is 72

Thanks for the input. They did come and replace the connections at the weather head, but perhaps there is a problem at the pole.

Assuming it is an open (or high resistance neutral (at the pole) I should be able to read a voltage on the neutral at the panel right?

 

[apauling]

Re: One leg 168 volts, other is 72

if a neutral becomes open or sporadic at supply, voltage read may be through series of device (s) back to neutral, rather than back to supply. too many variables.

if you have 220 across phases and not 110 (120) each leg, and all panel connections are tight, turn off all breakers (if main, access supply lugs) and if still no 110 each leg, it is power supplied by provider. loose connection, variable, bad transformer. line taps will work loose.

 

[hurk27]

Re: One leg 168 volts, other is 72

I would stay on this as a open neutral does cause many house fires, and this should be treated as a very dangerous situation. Get the POCO out there to check the pole connections ASAP!!! Demand that they tell you what happen as it has probably caused damage to some of the electronics in this house that the home owner should not have to pay for. But that is a fight that the home owner will have to take up with them. Also if this is a newer house with GFCI's and wired smoke detectors. you might want to do a through checking to show what all should be replaced.

 

[sfav8r]

Re: One leg 168 volts, other is 72

Thanks for all your input. I met PoCo this AM at the property. They again stated that the neutral "checked out fine."

As I couldn't sleep last night thinking about what other than an open neutral this could be, I came prepared with circuit drawings I did and asked them to please indicate what other than an open neutral could cause these symptoms.

I was very surprised by the results. As he attempted to explain all of the things that it could be, he kept interrupting himself saying "well, no that wouldn't do it." Finally he said he would grab the boom and take a look at the connection at the pole.

No surprise that there was major corrosion.

At any rate...problem solved. Appliances seem to have survived, garage door opener and two fluorescent fixtures didn't, but PoCo has agreed to reimburse owner for these items as well as my time.

Thanks again for the help.

 

[charlie]

Re: One leg 168 volts, other is 72

Sometimes, our trouble men are hard headed . . . HMMM . . . just like saying that sometimes, electricians are hard headed.

Bottom line, if this kind of problem exists on the whole house, a loose neutral has to be the problem. It may be between the service point all the way to the point in the service equipment where it lands. If not, it has to be between the electric utility's transformer and the service point. Don't let the trouble man leave without checking all the neutral connections until he finds the problem.

 

[hurk27]

Re: One leg 168 volts, other is 72

Charlie
You should see me go around with some of the POCO's service men up here. It's that first few word's out of there mouth that kill's me

"I have been doing this for 15 year's!!!"

I just say "so" Now what we still have a problem and your not going to tell me that you automaticly know the problem with out doing any trouble shooting. I do have a few friend's higher up and once in a while I have to call them to get the problem solved but in no case I will leave a job where we have a bad neutral. Or i'll just turn off the power untill the utillity can get there to fix it but I'll leave my cell number with the home owner so they can let me know when they there.

 

[charlie]

Re: One leg 168 volts, other is 72

Wayne, I would love to argue with you but I am reminded of the statement, "My mind is already made up, don't confuse me with the facts!" The bottom line is, we all get stubborn at times (not me, of course). It seems like our trouble men were born with a stubborn streak . . . but then again, they are not always wrong either.

 

[bennie]

Re: One leg 168 volts, other is 72

All of the utility service personnel I know, would automatically check the connections of the neutral, when informed of the voltage differential.

This is a slam dunk for a trouble shooter. The problem can be diagnosed over the phone.

It is unfortunate to have untrained individuals, and it is not the norm.

 

[charlie]

Re: One leg 168 volts, other is 72

It is unfortunate to have untrained individuals, and it is not the norm.

Bennie, these are not untrained people. At IPL (and I assume other electric utilities), a trouble man is a Class A lineman with a lot of years of experience. The experience has been building new lines or rebuilding old lines not troubleshooting. They get a few weeks of training and then turned loose to work their quadrant of the city. This training is on top of all the years of knowledge that they already have.

It is only after running into this problem that they understand what has happened. It is only after they have been run though the ringer do they have the new experience to see the problem.

 

[bennie]

Re: One leg 168 volts, other is 72

Charlie: My point is; if a lineman/serviceman can not determine the problem from the voltage imbalance, he is untrained.

The local service personnel will immediately go to the transformer and check the connections to the tank and MGN.

The tank connection can affect all drops from the transformer. The MGN connections are one connection per neutral. One loose or corroded joint will only affect the one neutral.

With four drops, from one pot, and only one neutral has failed, means the connection at the MGN is the problem. If all four drops are affected, the problem is at the tank connection.

 

[hurk27]

Re: One leg 168 volts, other is 72

Charlie argue with you! No Way!
I would never expect you to have a problem with a bad neutral in figuring it out.
but I have had a few (very few) service men that I ran into that didn't have a clue. In one case I was called by a home owner that said the utility said it was on her side of the service after running a few test that showed the neutral loss on the utility's side I told here to call them back. they again told her it was on her side. after the second time I was waiting for the service man to show up and after about a hour and a half I started to leave when I saw him coming down the alley and I just got out of my truck and snook to the corner of the house to see that he was just checking the voltage between the two hots he then made the remark that the electrician was nut's because he had 240 volts so how could there be a bad neutral. this is when I came around the corner and asked him how long has he been trouble shooting service's. he said about a year. after showing him what to look for he was in shocked as he didn't even know that there would still be 240 volts on the hots with the loss of the neutral. I turned off every other breaker in the panel then lifted the water ground to show him that there was no neutral connection at the MGN. when he saw the voltage go to 0 volts on one leg and go to 240 volts on the other he now understood why this can be so dangerous as all the grounding also had 120 volts to earth too. There are a few houses that don't have a water ground to keep the balance. like this house had. But it was corroded and this was the reason it showed up in the first place. After this we became good friends. But there are allot of good service men out there and I have learned from them as well. I was just saying that if you know what you have found in testing then somtime's you have to stick to it untill proven other wise.

And yes I do have a stubborn streak but I use it to error on the side of safty.

 

[sfav8r]

Re: One leg 168 volts, other is 72

For the record.

I think the lineman was probably well trained. He did check (and changed) the connections at the weatherhead, so he (the first guy) suspected a neutral from the start.

The mistake he made was not being thourough enough to check the connections at the pole. A lot of times these guys are under a lot of time pressure. I'm not suggesting he made the right call, I'm just saying he's human.

The second guy, I assume, was operating under the assumption that the first guy had eliminated the neutral as a possability.

As annoying as it is sometimes to get the PoCo to realize there REALLY is a problem, my guess is they get called much more often from people who think it's the PoCo when it's not.

I seem to recall making a poor decision or two in the field myself. Of course that was a long time ago

 

[karl riley]

Re: One leg 168 volts, other is 72

To check the weather head and not the pole connection with these symptoms to me means dereliction of duty or else incompetence. And yes, we are all human. So?

I write this after many frustrating interactions with utility men at all levels. Some of those men were very cooperative and knowledgeable. Some not. True anywhere, I suppose.

Karl