Neutral/grounded conductor issue

[Anudder Sparky]

I present for your consideration and input:
Customer states that lights throughout the residence are flickering/dimming and that small kitchen appliances are not functioning correctly.
I arrive, check voltages A to B, A to N, B to N & A/B to G at the utility pole. Everything checks out and all connections are tight. Underground feed is approx 120' to the residence.
At the panel all connections are tight at the main breaker, neutral bar, ground bar, branch circuit breakers and bussing.
Kitchen has 2- 20 amp small appliance circuits. I power up the microwave and check voltage on the circuit; voltage drops to 90 volts after 1 second of the micro running. Voltage returns to 120 when micro shuts off. Same issue on the other appliance circuit when the air fryer is turned on; voltage drops to 90 until air fryer is turned off. This anomaly is seen at the breaker AND the line side of the main breaker BUT NOT at the utility pole. The other odd part is that when voltage drops to 90 on A phase the voltage increases to 140+ on B phase and viceversa. (The neutral is not floating in the panel but that shouldn't cause this type of issue now)
HO has been at residence for 5 years, no work has been done on the kitchen circuitry and this issue just started last week.
My thoughts are that the neutral/grounded conductor between the utility pole and the panel has been compromised......or am I missing something???

I am interested to hear if any of you have encountered this and what possible solutions there might be.

TIA

 

[don_resqcapt19]

That is the classic indication of a problem with the service neutral. As far as not seeing it at the pole, this problem on shows itself when there are loads that are drawing current. Where there loads drawing current when you checked at the pole?

 

[LarryFine]

The other odd part is that when voltage drops to 90 on A phase the voltage increases to 140+ on B phase and viceversa. (The neutral is not floating in the panel but that shouldn't cause this type of issue now)

This is the only odd part that does matter. Your neutral is behaving like it's floating.

 

[Anudder Sparky]

That is the classic indication of a problem with the service neutral. As far as not seeing it at the pole, this problem on shows itself when there are loads that are drawing current. Where there loads drawing current when you checked at the pole?

My bad, I left out that minor detail; no, the voltage issue was not found at the utility pole.

 

[Anudder Sparky]

This is the only odd part that does matter. Your neutral is behaving like it's floating.

Ok...but why wouldn't this issue manifest itself immediately after the original wiring of the home? Home was constructed 15 years ago, the issue just started last week...

 

[Fred B]

Overhead or underground service conductors?

 

[Anudder Sparky]

Overhead or underground service conductors?

Under

 

[retirede]

Ok...but why wouldn't this issue manifest itself immediately after the original wiring of the home? Home was constructed 15 years ago, the issue just started last week...

Deterioration of the neutral underground.

 

[LarryFine]

Ok...but why wouldn't this issue manifest itself immediately after the original wiring of the home? Home was constructed 15 years ago, the issue just started last week...

Because something changed last week, or just reached the failure point after 15 years, possibly from a minor damage when it was installed.

That's what troubleshooting is all about: finding what has changed and restoring it.

 

[Fred B]

Seen just recently underground conductor minor damaged of insulation during installation that after 15yrs gave out.

 

[Fred B]

A thumper will find it easily.

 

[Anudder Sparky]

Here's the other point that is bothering me; since the grounded conductor and the grounding conductor are bonded at the panel wouldn't it make sense that there would be a solid path to ground even if the grounded conductor was compromised underground...the cold water bond is 12" from the panel and visible, the ground rod is 6' away on the exterior.

 

[Anudder Sparky]

A thumper will find it easily.

I'm not familiar with that term "thumper"....other than it relates to a jumping jack/compactor.

 

[Fred B]

A pulse generator ground fault locator and A-frame.

Used one to find that pictured break. Located 3.5ft down within 6 inches.

 

[Little Bill]

You have the classic symptoms of a lost/damaged neutral conductor. The proof is you had 90V on one leg and 140V on the other. Add those and you have 230V. Depending on the transformer and other loads on it, 230v is within range. You probably won't see the problem at the pole without having a load on the system at the time of measurement.

A "thumper" was suggested since you mentioned the service was UG. A "thumper" is just a term for a tester that sends a signal out that can be traced. The signal part is what the term "thumper" is referring to. You can find the broken part when the signal changes. The meter on the tester will change directions when you go past the break. You just keep moving the probes until you "zero" in on the exact location.

 

[LarryFine]

Here's the other point that is bothering me; since the grounded conductor and the grounding conductor are bonded at the panel wouldn't it make sense that there would be a solid path to ground even if the grounded conductor was compromised underground...the cold water bond is 12" from the panel and visible, the ground rod is 6' away on the exterior.

A solid path to ground? You mean the earth around the house?

That path has way too much resistance to carry neutral current effectively.

 

[retirede]

Here's the other point that is bothering me; since the grounded conductor and the grounding conductor are bonded at the panel wouldn't it make sense that there would be a solid path to ground even if the grounded conductor was compromised underground...the cold water bond is 12" from the panel and visible, the ground rod is 6' away on the exterior.

The neutral current must return to the transformer, not the dirt.

 

[texie]

As I always say with these classic weak and/or intermittent neutrals, better find it real soon or a lot of magic smoke is coming. Can get real expensive.

 

[mtnelect]

Do It Yourself "Wire Tracer"

When in my apprenticeship worked with a journeyman doing irrigation wiring repair on golf course's. Remove one of the sparkplugs wires from the service truck, attach a wire from the sparkplug wire to the irrigation wire. Then take a portable radio tuned to a blank station and follow the popping sound to it stops. You have found the break !

 

[Dennis Alwon]

I have the utility out to a job twice telling me there wasn't an issue. I called the power company engineer and explained the issue and he said "That's a classic neutral problem". I told him I had their guys out twice and I told them that it was a neutral problem. They had it fixed that day.

The problem is if they aren't testing it under load then they will not see the problem.