Power Company Loose Neutral?

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mkgrady

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Massachusetts
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 said:
It seems more probable that you have one phase that is bad not the neutral.
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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
 
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!
 
mkgrady said:
I don't understand why that would be. Can you explain?
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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.
 
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.
 
jaylectricity said:
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.
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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 said:
Dennis,

Which voltage is normal?
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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 said:
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.
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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.
 
mkgrady said:
Name is Mike (not Dennis). Neither voltage is normal. Each leg should be 120 to ground and 240 between legs.
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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.
 
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.
 
al hildenbrand said:
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.
Click to expand...

Thanks for all the replies, Al, I hope you're right
 
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.
 
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.
 
al hildenbrand said:
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.
Click to expand...

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.
 
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