Power Company Loose Neutral?

[mkgrady]

Went to a customers home today and found symptoms of a loose neutral. This is my first experience with this type of problem. I found what I think leads to an indication of the incoming line having a bad neutral. The voltage on the service legs would go up and down as different loads would come on and off. The clue (I hope) that tells me the problem is out on the street is that the GEC had substantillly more current on it than the service neutral. The following is a set of readings at the main service panel: A leg to N 145 volts, B leg to N 96 volts, A leg current 8.4 amps, B leg current 14.7 amps, neutral current 2/10ths amps and finally GEC current 4 amps. I'm thinking the neutral is loose out on the street because of the high current on the GEC. Am I on to something? The customer is going to call the power company to check their neutral before I look any further.

[Dennis Alwon]

It seems more probable that you have one phase that is bad not the neutral.

[mkgrady]

It seems more probable that you have one phase that is bad not the neutral.

I don't understand why that would be. Can you explain?

BTW, this same customer recently did have a bad leg coming to the service, The POCO came out to check it and said everything was OK. They had voltage but when the current went up the connection opened. I followed up and found there was a bad splice on the POCO pole. I could see the charred splice with my binoculars. The POCO came back out ans fixed the splice which took care of their problem. Here I am back 2 months later with what seems to be a loose neutral

[jaylectricity]

Well if electricity takes the path of the least resistance, and the least resistance seems to be leading into the earth as opposed to finding it's way back to the POCO's grid I would think that the problem is with the neutral. Not necessarily the nuetral out on the street; maybe it's within the service equipment.
I'm not a service technician so don't take my words for absolute, but it sometimes amazes me how much electricity we can pull off the significantly undersized feeders coming off the pole. I understand that heat dissipates much easier outside, but still it amazes me.

Jay

PS yeah I know I used "amaze" twice
PPS It took me a couple of threads to figure out what POCO meant!

[Dennis Alwon]

I don't understand why that would be. Can you explain?


If one leg to neutral is reading accurately then I don't think it is a bad neutral. One phase to netral works fine but the other phase to neutral is low. If the neutral was bad it would more than likely cause low similar readings on both phases. My bet is a bad phase.

[al hildenbrand]

I had a similar set of voltage symptoms on a single family dwelling.

If the voltage swings are present on the line side of the PoCo meter, then the PoCo needs to find their bad connection.

[stevedonovan2]

PPS It took me a couple of threads to figure out what POCO meant!
I'm still trying to figure it out...:-?

[al hildenbrand]

Dennis,

Which voltage is normal? A leg to N 145 volts, B leg to N 96 volts,

[mkgrady]

Well if electricity takes the path of the least resistance, and the least resistance seems to be leading into the earth as opposed to finding it's way back to the POCO's grid I would think that the problem is with the neutral. Not necessarily the nuetral out on the street; maybe it's within the service equipment.


The service panel is in real good shape and all neutral connections are tight. Same with the meter socket. I just can't figure how the loose neutral could be in the house under these conditions.

[al hildenbrand]

I'm still trying to figure it out...Power Company :smile:

[mkgrady]

Dennis,

Which voltage is normal?

Name is Mike (not Dennis). Neither voltage is normal. Each leg should be 120 to ground and 240 between legs.

[Dennis Alwon]

Dennis,

Which voltage is normal?

You have a good point. 145 is very high, 96 is very low. I really didn't grasp the 145 volts, got stuck on the 96. I'm still going with a bad phase.

[Dennis Alwon]

Name is Mike (not Dennis). Neither voltage is normal. Each leg should be 120 to ground and 240 between legs.
Mike- Al was talking to me

[mkgrady]

If one leg to neutral is reading accurately then I don't think it is a bad neutral. One phase to netral works fine but the other phase to neutral is low. If the neutral was bad it would more than likely cause low similar readings on both phases. My bet is a bad phase.

Neither leg is reading normal voltage. The only time the correct voltage is present is when the main breaker is turned off. Normal voltage is 120, 120 and 240 leg to leg. I still think it is a loose neutral on the POCO side but I'm not smart enough to explain why.

[al hildenbrand]

Name is Mike (not Dennis). Neither voltage is normal. Each leg should be 120 to ground and 240 between legs.Hi Mike.

I'm sorry that I confused you. I was attempting to direct my comment to Dennis Alwon, so he could comment.

I agree with you that the PoCo has some investigating to do on their own lines. The key, for them, that is irrefutable, is that the voltage is swinging on the line side of any connections owned by the customer.

In my area, with an overhead service, the PoCo makes the splice from their drop to the service entrance conductors at the weatherhead on top of the mast. So all I have to do is read the voltage swing on the line side of the meter. We use internal bypass meter bases here so it is easy to pull the meter while the service is under load, and, with the meter out, measure the voltage.

It is standard operating procedure here. . .but not every where.

My point about the voltage measurement is universal.

[al hildenbrand]

Mike,

Don't worry about telling the PoCo about the current on the GEC. . .

The voltage swing, under load, on the line side of the meter says it all.

[mkgrady]

Mike,

Don't worry about telling the PoCo about the current on the GEC. . .

The voltage swing, under load, on the line side of the meter says it all.

Thanks for all the replies, Al, I hope you're right

[al hildenbrand]

Mike,

Try drawing the circuit for the service.

Transformer secondary winding with a center tap.

The transformer centertap, besides being connected to the grounded service conductor, has a conductor running down the pole to a ground ball (or butt plate, or ground rod) in the earth.

At the service disconnect, connect another conductor to a ground rod / water pipe / concrete encased electrode / etc. that is the house side earth connection.

Extend the two hot conductors to a pair of loads, one between each hot and the neutral.

Stick a 100 Ohm resistance in the neutral on the line side of the meter. . .

Then move the 100 Ohm resistance to the load side of the service disconnect.

[al hildenbrand]

Oh, yeah.

Remember that the earth connection of the Pole ground and the dwelling grounding electrode system will mean the current path through the earth is from 50 to 500 Ohms. That's a gob larger than the resistance of the neutral itself when the connections are good.

[mkgrady]

Mike,

Try drawing the circuit for the service.

Transformer secondary winding with a center tap.

The transformer centertap, besides being connected to the grounded service conductor, has a conductor running down the pole to a ground ball (or butt plate, or ground rod) in the earth.

At the service disconnect, connect another conductor to a ground rod / water pipe / concrete encased electrode / etc. that is the house side earth connection.

Extend the two hot conductors to a pair of loads, one between each hot and the neutral.

Stick a 100 Ohm resistance in the neutral on the line side of the meter. . .

Then move the 100 Ohm resistance to the load side of the service disconnect.

Yup, I drew it out and it seems to confirm my initial thought. I also pictured this high resistance neutral down stream in the house on a multi wire branch circuit. (This was my only other theory) Appears it would cause the same voltage problems but it would be limited to the bad circuit not the whole service.

[al hildenbrand]

it would be limited to the bad circuit not the whole service.8-) Exactly.:smile:

[mkgrady]

8-) Exactly.:smile:

Thanks again Al. Now I can sleep soundly tonight.

[LarryFine]

The OP description of voltages is the epitome of a bad neutral. The fact that the two voltages add to 241 shows that it's the neutral, and not a phase.

[quogueelectric]

This is the textbook open or loose neutral. take a 240 volt battery and put 2 100 ohm resistors in series. each one drops 120 volts from a and b phase to the centertap. Now turn on annother light in the den and disconnect the neutral oh by the way the den light is on a phase. the 2 100 ohm loads in paralell equal a combined load of 50 ohms which is now in series with b phase which is 100 ohms. total circuit impedence is 150 ohms now so 80 volts will be dropped across a phase the heavier load and 160 volts across b phase the lighter 100 ohm load. Sound familiar?? the lighter load side will be hit with higher voltage until the devices connected burn ,short or open up and keep swinging the voltages back and forth until everything on the circuits are burned up. Unless the overcurrent protection devices exceed thier ampere trip ratings they will not trip. This is a very dangerous condition which should be addressed IMMEDIATELY!

[al hildenbrand]

quogueelectric,

Do you think the open / loose neutral is inside the house?

Back at post #0: The customer is going to call the power company to check their neutral before I look any further.Maybe Mike (mkgrady) can give us an update?

[cowboyjwc]

I had a problem once where I knew that it was a bad neutral (lights getting brighter under load instead of dimming, etc.) I even thought I knew which circuit it was. After about an hour and a half of looking I couldn't find anything. Finally I went outside and looked around and there was the neutral hanging by one strand at the pole.

Also found a tree growing around the drop one time, and by that I mean the drop was completly enveloped by the trunk, and one phase was broken inside of the tree.

Sometimes you have to think and look outside of the box.

[al hildenbrand]

Sometimes you have to think and look outside of the box.LOL

Literally! :grin:

[mkgrady]

The POCO had a loose neutral. They said it was a bad connection at the weatherhead. I think it was further upstream. While they were there they condemned the service entrance cable because it is aluminum. It turns out the customer had the service changed a couple of years ago without telling the power company or pulling a permit. The work was done to upgrade from 100 to 200 amps so central AC could be installed. I spoke with the POCO for my customer and they want the SE changed to copper to meet the town's standard. I'll do that some time soon.

Now why I don't believe the loose neutral was at the weatherhead: I was called to the customers house a few weeks ago for a different reason. They kept loosing power to half the house. The POCO had already been there and said their lines to the house were OK. They were not. The customer had been shutting off their MCB and resetting it each time they lost one leg. Of course they didn't know what they were doing but a neighbor suggested it and it did turn their power back on. After loosing power several times I was called. After spending 2 hours looking for a problem inside the house I looked at the OH POCO line feeding the house with binoculars. I could see a splice that was charred. I contacted the POCO and they came right out. They replaced the splice and the drop to the house from the nearest pole. The neutral they say was loose at the weatherhead was spliced by the POCO. They even borrowed my allen wrench to make it tight. I watched them crank it down. I suspect the loose neutral was further upstream on an old splice like the one that failed a few weeks ago. After I spotted the charred splice the POCO credited the customers account for the amount of my invoice. I suspect they did not want to have to do it again for the loose neutral so they blamed the CU/AL splice at the weatherhead. A good strategy on their part because the town doesn't allow aluminum.

[quogueelectric]

In my experience the open neutral is usually at the utility companys side. Hastily installed alluminum conductors you get the picture it can get really ugly. Usually a connection on the service latteral neutral. Unless you can see that the service was done by a real hack the grounding on all of the houses on the xformer would have had to all failed which is very unlikely but I have seen it happen on more than one occasion. 40 years ago anything would fly with the inspectors. The ground rod and waterpipe ground will clanp the voltage to a certain point however the more unbalanced the current gets the worse the condition becomes and the harder it is to hold the voltages at a stable level Once the ground connection becomes open the 240 volt xformer puts a phase and b phase into a dynamic series parallel circuit which is not the 120 volts the equipment is designed to operate at. Fire and burned out equipment usually result.

[quogueelectric]

The key here is also the voltages under load. When I was a little baby electrician I was sometimes fooled by the pwer would stabilize when you shed the load and everything seemed fine then you reconnect the load and all hell breaks loose.

[LarryFine]

The key here is also the voltages under load. When I was a little baby electrician I was sometimes fooled by the pwer would stabilize when you shed the load and everything seemed fine then you reconnect the load and all hell breaks loose.You're not the only one. Last week, we got called to a home with exploding bulbs and damaged electronics, along with the usual symptoms. The POCO guys swore the voltages were proper and there was no poor connection.

Too bad they only checked while the main breaker was off. :rolleyes: