Strange problem call today

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jwnagy

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Damascus, Maryland
I got a call from a friend today that he was having some problems with the power in his house (single phase). I went over and found a hundred ninety-eight volts on one phase and 57 volts on the other phase. I automatically assumed that he had somehow lost the neutral coming into the house. I went outside and removed the cover from the meter socket and check the power coming into the house (service drop). Everything looked the way it should, 240 volts phase to phase 120 volts ground to phase. When I went back into the house and looked at the panel I could not find any loose connections on the neutral bar or the neutral coming into the house on the lug. Everything seems to be the way it should.

What I find baffling is that exhibits all the symptoms of a lost neutral yet I cannot find a missing neutral. Turning switches on and off in the house affects other circuits. I find myself leaning in the direction of the power company yet the power company says that the power coming into the house is fine.

I'm also wondering if it could be a problem with the main breaker. I did find a little bit of water coming out of one phase lug on the main breaker which happens to be a 100 amp Cutler Hammer main breaker, and I wonder if the problem might be there. The service entrance cable is ancient, an old clothbound piece of service entrance cable installed in 1969. I've been telling him for a while that it needs to be changed and I hope that this convinces him. Water is apparently leaching through the outer cover and running down along the conductors into the panel but very slowly.

Any opinions out there on what the problem might be besides me being a big dummy. ?

By the way, I've been an electrician for nearly 40 years and a master in Maryland for the last 28 years. This isn't my first rodeo, but this one has me a little baffled.

Jeff
 
180927-2411 EDT

jwnagy:

Nothing particularly strange except inside you read 198 + 57 = 255 V, and outside read 240 V with each line to ground being 120 V. The inside reading should have summed to 240 V or the outside reading should have been 255 V with each line to neutral being 127 V.

Although you should do an inside line to line voltage measurement and compare that with the outside measurement. With with an incoming open neutral and a partially non-resistive load you might get a higher sum of the individual inside readings.

Your use of the word ground does not really tell me if it was really ground or neutral.

I believe your problem is between the outside neutral and the inside neutral bus bar. Measure the voltage between outside neutral where you previously did and called it ground, and the inside neutral main panel bus bar.

.
 
You measured the balanced voltage at the meter with the loads of the house on, right? And using the strands of the load-side neutral conductor, not the line-side or the meter enclosure?

Your imbalance numbers add up to 255v, not 240v, which is really weird if you got 240 at the meter. The load could have changed while measuring. What is the line-to-line in the panel?

If you measure the imbalanced voltages in the panel under the same conditions as you measure the balanced voltages in the meter, there must be a break in the neutral between the two.

Check for any voltage where it should be zero: between the neutral terminal and the neutral wire each place it's available. Don't assume a physically-tight connection has no resistance.


Added: Gar and I apparently think alike, even if we express it differently. You can use a long piece of wire to extend one voltmeter lead to measure between the outside and inside neutral points.
 
Bypass POCO, backfeed with Generator, see if problem persists.

If no back-fed breakers fix it, hunt down remodel J-box that tied nuetrals from all circuits under the same loose nut, or wad of tape.
 
Larry, thanks for the reply.

Let me clarify a bit. I say 120/240 in a nominal way. I can't remember what the exact voltage readings were, just that they seemed ok.

Its single phase and I took readings on the line side and load side of the meter with meter in and out. Readings looked fine.

I shut the main off and took a voltage reading phase to phase and phase to ground/neutral in the panel. Since they are on the same bar, I'm using the term interchangeably. If it was past the panel I would have made the distinction. The voltages looked good.

I turned all of the breakers off and turned the main on. I turned each breaker on in turn and took readings phase to phase and phase to ground each time. The voltage readings changed when each single pole breaker was turned on, according to the loads on each circuit. The circuit for the attic affects the voltage the most. It has a condensate pump and attic fan on it. I checked in the attic and nothing seems out of the ordinary.

Two pole breakers did not seem to affect the readings.

I checked all of the connections on the neutral/ground bar. All were tight and showed no signs of looseness.

The load side service entrance cable is 6 feet long, from the meter to the panel, is 6 feet long and shows no sign of physical damage.

I also wanted to add that the home owner said he could feel a tingle when he touched the water faucet. Just for heck of it I plugged in a plug tester to a circuit and it indicated a bad ground. In addition to the neutral, I've checked all the connections for the grounding conductors and they are in order. BTW the house is on a well.

The whole house is affected, not just one circuit. I'm wondering if the neutral is lost coming into the house from the poco but is trying to flow back through the grounding conductors, hence the tingle when water pipe is touched.

Im wondering if i pulled the meter and disconnected the load side grounded conductor from the lug in the meter that should tell me what I need to know?
 
jwnagy said:
Its single phase and I took readings on the line side and load side of the meter with meter in and out. Readings looked fine.
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The voltages will always measure equal with no load, so that's meaningless. It's the imbalance in load resistances, and thus the load currents, that produce the imbalance in voltages. I once had to educate POCO guys about that.

I shut the main off and took a voltage reading phase to phase and phase to ground/neutral in the panel. Since they are on the same bar, I'm using the term interchangeably. If it was past the panel I would have made the distinction. The voltages looked good.
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Again, without loads, matched voltages are expected. Even the earth alone is enough of a connection from the neutral and grounding electrodes to the POCO neutral to maintain matching voltages.

I turned all of the breakers off and turned the main on. I turned each breaker on in turn and took readings phase to phase and phase to ground each time. The voltage readings changed when each single pole breaker was turned on, according to the loads on each circuit. The circuit for the attic affects the voltage the most. It has a condensate pump and attic fan on it. I checked in the attic and nothing seems out of the ordinary.
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Expected, and evidence that what I said is accurate.

Two pole breakers did not seem to affect the readings.
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Also expected, because line-to-line loads do not affect line-to-neutral currents (with minor exceptions, such as a running clothes dryer).

I checked all of the connections on the neutral/ground bar. All were tight and showed no signs of looseness.

The load side service entrance cable is 6 feet long, from the meter to the panel, is 6 feet long and shows no sign of physical damage.
Click to expand...
So far, so good.

I also wanted to add that the home owner said he could feel a tingle when he touched the water faucet. Just for heck of it I plugged in a plug tester to a circuit and it indicated a bad ground. In addition to the neutral, I've checked all the connections for the grounding conductors and they are in order. BTW the house is on a well.
Click to expand...
The tingle indicates a voltage difference between the neutral, which it bonded to the plumbing, and earth, further proving a break in the neutral. The earth alone is not enough to keep the neutral at zero volts with loading greater than a voltmeter.

The whole house is affected, not just one circuit. I'm wondering if the neutral is lost coming into the house from the poco but is trying to flow back through the grounding conductors, hence the tingle when water pipe is touched.
Click to expand...
The whole house being affected shows that the issue is upstream of the neutral bus in the panel. The tingle is a sign that there is voltage on the neutral despite the plumbing and grounding electrodes.

Im wondering if i pulled the meter and disconnected the load side grounded conductor from the lug in the meter that should tell me what I need to know?
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No. What you should do is again measure voltage balance at the meter when you are reading the voltage imbalance inside. If the imbalance is present in the meter now, the issue is the POCO's problem.

If you read balanced voltages at the meter while reading imbalanced voltages at the meter, it's your problem. That's when you start looking for voltage between the meter neutral and the panel neutral.

I'm guessing you will find the problem is on the POCO side of the meter, especially if it's an underground service, but likely either way.
 
It shouldn't matter. For this purpose, the meter is not relevant. It should read like a good 2-pole breaker or a pair of good fuses.

You can read from either the line or load side of L1 to the neutral, and likewise, from either the line or load side of L2 to the neutral.

What would be more telling would be, again with house loads causing the imbalance to be apparent, to measure from the line side of the neutral to the load side of the neutral. If there's any voltage, the neutral connection within the meter is where the problem is.

Of course, the meter must be in place for these tests, so be careful to not touch more than one terminal at a time.

The basic problem is that there is a break in the neutral somewhere between the utility transformer and the panel neutral bar. Your mission is to locate that break by seeing where expected measurements are and where problem-indicating measurements are.
 
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LarryFine said:
..measure voltage balance at the meter when you are reading the voltage imbalance inside. If the imbalance is present in the meter now, the issue is the POCO's problem...
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Thanks Larry, that's easier than hooking up a generator, and one less knuckle in my knuckle head.
 
I think the neutral conductor within that SE cable has discinerated.

A couple years ago I had a guy call having problems with his stove. There was a SE cable used to feed his stove receptacle that ran thru a crawl space and it was not supported to the joists. Part of it laid on soil, and wouldn’t you know it; after cutting the jacket off where it touched the soil it revealed neutral strands that were reduced to fine looking hairs until there was no connection left. Crazy.
 
my $$'s on bum noodle here JW

the only thing i might add to your assessment is asking for a wiggy, non-digital meter to do so


~RJ~
 
jwnagy said:
Thats a new expression to me "bum noodle". Explain please ?

Why a doggy instead of fluke or similar digital? I'm curious.
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I think he is referring to a bad neutral.
A Wiggy, or solenoid-type tester (Mine is an Ideal Vol-Con), does not read misleading capacitive voltages, that some digitals will. However, it also won't give you a good reading about imbalances. It's better suited to "hot or not" and "120 or 240" type testing.
 
Have you asked the POCO to check the service drop with a Beast of Burden? Pretty common test if the service is in question. Beast will load to 30A and a Mega-Beast will load to 80A.
 
meternerd said:
Have you asked the POCO to check the service drop with a Beast of Burden? Pretty common test if the service is in question. Beast will load to 30A and a Mega-Beast will load to 80A.
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The POCO is unlikely to respond unless the OP provides compelling grounds to do anything. Finishing up by measuring the inside neutral connection against the outside connection is the final piece of the puzzle. If that reading is zero, or close to, then it's the POCO neutral that's bad. Otherwise it's the SE neutral connection, or something in the meter can.
 
jwnagy said:
Why a doggy instead of fluke or similar digital? I'm curious.
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Low impedance. if your meter has a low impedance feature it will work otherwise use a wiggy, you can also try a wiggy and multi meter at the same time.

Roger
 
roger said:
Low impedance. if your meter has a low impedance feature it will work otherwise use a wiggy, you can also try a wiggy and multi meter at the same time.

Roger
Click to expand...

That's a fun experiment.

I settled on Flukes T+Pros a few years ago. We all have the same so we can all relate. I used three on a problem circuit and it was interesting to see the voltage would change depending where the meters were placed. They are not low impedance but do put more load on a circuit than my 87s.
 
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