second opinions on apparent mains neutral issue

Thread Starter

ebeowulf17

Joined Aug 12, 2014
3,307
The only place all neutral and ground circuits should be bonded is at the mains panel. 240 VAC appliances like a stove, drier, air conditioner or electric heaters should have their own L1, L2, Neutral and Ground at the load center. I have seen a few instances where on installation shortcuts where taken and later resulted in strange problems. Examples where a neutral for example was shared and should not have been. Things go along fine for years right till a bonded connection in a box somewhere gets overloaded or simple becomes loose with age. The trick to trouble shooting becomes trying to figure out which branch circuits go where which is a challenge since the wires are in walls.

My guess is the power company will show up again and run a load test at the point where their responsibility ends. Then the problem gets placed back in your lap. I don't see where the symptoms you have will be a result of a hot (L1 or L2) with a fault but think your symptoms point to a neutral. The problem lies in not actually seeing how everything is distributed in your residence. :(

Ron
Even in those examples with inappropriately shared neutrals and such, shouldn't a solid neutral connection to the neutral from the utility ensure that the neutral voltage at the entrance to the breaker panel is still good?

I totally understand that there are a lot of ways for sketchy wiring to compromise individual circuits (or groups of related circuits sharing a common neutral,) but I don't see how any of that would push the neutral at the panel entrance around, unless there was a problem between the utility and the panel entrance.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
My example is where for example it was once mandatory for all kitchen outlets had to be fed from both L1 and L2 with a common shared neutral.
In this case of course the neutral current would be zero if the top 120v appliance was identical to the bottom outlet appliance, then the neutral current would be zero.
If two mismatched appliances were plugged in to one outlet and the neutral connection became loose then one outlet voltage would rise, I have seen this happen.
Max.
 

Thread Starter

ebeowulf17

Joined Aug 12, 2014
3,307
Do you have a good earth ground on your panel? Has it been megged to test the grounding? You need a licensed electrician to open the panel and check it. The power company stops at the meter. Anything after their meter is your problem and not theirs is their attitude. IE "It's not my job!" Even with good wiring, without a proper ground, you have problems. Bad earth resistivity, badly corroded ground rods, bad ground wire to rod clamps, bad ground wire to panel connection, lots of ways to have ground problems which appear as a neutral problem.
I'm intrigued by this - I sort of imagined the ground rods and the utility neutral as backing each other up, providing redundancy. I would've thought that even with a dubious ground rod, the neutral coming in would take care of things. It's only maybe a 50ft run from my mast to the power pole and transformer, which has its own grounding rod at the base of the pole.

As for the quality of my ground rod, it hasn't been professionally checked. I did take my own resistance and voltage readings from the neutral in the panel to the top surface of the ground rod and basically found the voltage and resistance too low to measure... and since the neutral is clearly dancing around some, that would seem to imply that the ground rod isn't doing a very effective job.

Since several of you now have mentioned using pipes as a reference, I'll take a closer look at my plumbing and see if I can make sense of it. It's a weird house with lots of pipes coming and going for outdoor hose spigots, irrigation, etc, and thus far I haven't identified the meter or entrance, but I didn't try that hard. I'll take a closer look and report back.
 

SamR

Joined Mar 19, 2019
5,031
mentioned using pipes as a reference, I'll take a closer look at my plumbing and see if I can make sense of it.
I threw away all my NEC books when I retired, but the preferred method is a ground rod. Or at least mine is/was. I dealt with 4-20mA analog instrument signals and grounding signal cable sheaths and instrument chassis' was always a concern. There is also an issue of "floating ground potential" with multiple ground points that are not close to each other (within 6' or so). Also, if you do have an electrician go into your panel have him add a panel surge suppressor. It's better to catch those lightning-induced power line spikes and surges at the panel than just rely on surge suppressor power strips and they are relatively cheap. https://www.amazon.com/dp/B008VM6MXI/ref=psdc_3236443011_t2_B01AQAKRSS

Well, they used to be cheap. They seem to have gotten a bit pricey since I last bought one and more sophisticated. Still much cheaper than a blown digital TV or Microwave. 3 wires, L1, L2, GND. Easy-peasy install.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Yes, but there's a mix of copper and galvanized pipe in the house, so there are several dialectric unions and I'm not totally sure which, if any, pipes in the house might be meaningful ground references.
The ground may not be perfect, but from what you have posted so far appears to me to point to bad neutral connection(s) some where.
Max.
 

MisterBill2

Joined Jan 23, 2018
18,176
One simple and easy thing is to check the tightness of ALL the neutral connections, including in the breaker/fuse panel where that tie-bar with all of the white wires connects to the neutral incoming wire. often that assembly is more than one piece. Probably it would be good to switch off the mains while doing the checks, in case something opens up. And, if you have a digital AC voltmeter, check the voltage between the incoming neutral wire and the bar with all of the white wires attached to it. That voltage should be zero. Also check from each incoming phase to the neutral and see if that value changes. You may see stability, or possibly not. Just be careful to not touch any live parts of the system while you are measuring.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
One simple and easy thing is to check the tightness of ALL the neutral connections, including in the breaker/fuse panel where that tie-bar with all of the white wires connects to the neutral incoming wire. often that assembly is more than one piece.
Covered in Post #17! ;)
Max.
 

Tonyr1084

Joined Sep 24, 2015
7,853
check the tightness of ALL the neutral connections
In addition to that I'd recommend checking all wire nut connections as well. I've found that the most common point of "loss of connection" is at those wire nut junctions. Heat expansion and cold contraction work to loosen them. Hopefully you don't have any hidden junctions like my house apparently has. HAD! There may be more as yet undiscovered.
 

Thread Starter

ebeowulf17

Joined Aug 12, 2014
3,307
One simple and easy thing is to check the tightness of ALL the neutral connections, including in the breaker/fuse panel where that tie-bar with all of the white wires connects to the neutral incoming wire. often that assembly is more than one piece. Probably it would be good to switch off the mains while doing the checks, in case something opens up. And, if you have a digital AC voltmeter, check the voltage between the incoming neutral wire and the bar with all of the white wires attached to it. That voltage should be zero. Also check from each incoming phase to the neutral and see if that value changes. You may see stability, or possibly not. Just be careful to not touch any live parts of the system while you are measuring.
Covered in Post #17! ;)
Max.
In addition to that I'd recommend checking all wire nut connections as well. I've found that the most common point of "loss of connection" is at those wire nut junctions. Heat expansion and cold contraction work to loosen them. Hopefully you don't have any hidden junctions like my house apparently has. HAD! There may be more as yet undiscovered.
I'm clearly the odd man out here, since it seems like many of you agree that this is a possible culprit... but I don't understand how or why. Bad neutral connections with wire nuts within branch circuits, or where branch circuit neutrals join their bus bar in the breaker panel, would certainly explain bad neutral behavior on their respective circuits, but how would they explain bad neutral behavior at the service entrance to the breaker panel?

I'm reading voltages right where the wires from the meter above enter the panel, and the neutral there is moving by 3-4V. If there were good connections from the utility, through the mast and the meter, down to the panel entrance, I would expect the neutral there to be very stable.

What am I missing here? Are you guys saying that wiring faults on branch circuits actually could cause the neutral readings where the neutral first enters the panel from the outside world to be inconsistent? If so, how? When there's a loose connection, you expect unpredictable, floating voltages on the side that's left floating (in this case the branch circuits' neutrals) but not on the side that's still connected to something solid (in this case the neutral at the service entrance.)

Don't get me wrong - I'm not saying it's a bad idea to confirm that the other neutral connections are solid, that there are no hidden joints within the walls, etc. These are all good practices, obviously. I just don't see how they would explain bad readings at the service entrance.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Way back in the UK when I did installations there, the neutral was not connected to earth ground at the consumer panel and could not come in contact with each other anywhere in the system.
In order to measure the validity of the ground conductor back to the earthed star point where it was connected to the neutral, we would use a resistance Megger between the GND and the neutral and measure the whole loop back to the transformer.
Max.
 

Tonyr1084

Joined Sep 24, 2015
7,853
I'm reading voltages right where the wires from the meter above enter the panel, and the neutral there is moving by 3-4V. If there were good connections from the utility, through the mast and the meter, down to the panel entrance, I would expect the neutral there to be very stable.
Does the neutral come down from the mast directly into your box? Or is there a junction somewhere between? I've almost no experience with incoming power but I can understand your confusion. Up to this point I was imagining you were finding problems downstream in the circuitry. But paying closer attention to your last post, I'd be hard pressed to come up with any other explanation other than the possibility of a weak neutral connection between the meter and the panel.

Years ago I was in an apartment. Half the power would go out. I'd switch on the electric stove and that would restore power to the other half. How? By drawing so much load that the weak L1 (or L2) connection would temporarily bond. It would break down again, but it was in the meter box itself. And it took three weeks to find. Once found it was an easy fix - just tighten up the connection. It had worked its way loose.

I can only guess, but I'm thinking (now) that there's a loose connection either in the meter box or in the panel. Given that you've probably already checked all the connections to the neutral, I'd guess it is probably in the meter box. Unless the neutral runs straight from the mast all the way into the panel without interruption.
 

SamR

Joined Mar 19, 2019
5,031
As to checking wire connections. At some point manufacturers went to wire stabs on switches and outlet bodies. IE you stripped the wire and stabbed it into a hole on the device. The connection for them while UL approved is considered by many to be inadequate. In addition to the stabs they also still had the screw connections that are considered to be the better method of attachment. Considered better due to more wire surface area contact on the screws than the stabs and therefore more protection against any surface corrosion.

Edit: IF aluminum wiring used (which I do not recommend) it is IMPERATIVE to use a compound on the wire before connecting. Can't remember what that stuff was called...
Aluminum wiring is becoming more common in houses for appliance hi amperage 240V feeders (stoves, water heaters, etc) and common for the feed from transformer to house panel.
 
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Thread Starter

ebeowulf17

Joined Aug 12, 2014
3,307
Does the neutral come down from the mast directly into your box? Or is there a junction somewhere between? I've almost no experience with incoming power but I can understand your confusion. Up to this point I was imagining you were finding problems downstream in the circuitry. But paying closer attention to your last post, I'd be hard pressed to come up with any other explanation other than the possibility of a weak neutral connection between the meter and the panel.

Years ago I was in an apartment. Half the power would go out. I'd switch on the electric stove and that would restore power to the other half. How? By drawing so much load that the weak L1 (or L2) connection would temporarily bond. It would break down again, but it was in the meter box itself. And it took three weeks to find. Once found it was an easy fix - just tighten up the connection. It had worked its way loose.

I can only guess, but I'm thinking (now) that there's a loose connection either in the meter box or in the panel. Given that you've probably already checked all the connections to the neutral, I'd guess it is probably in the meter box. Unless the neutral runs straight from the mast all the way into the panel without interruption.
From the mast, it goes to the meter, and then from the meter straight to panel.

I thought I'd checked all I could, but I'm going to double check again in the next few days. I can't check the meter end of the wire, but I can double check the panel end of that neutral wire one more time.

The utility is planning to do a load test which is meant to verify that everything from their side up to the meter is in good shape. Of course, with it being an intermittent problem, my fear is that it tests ok while they're here and then misbehaves again after they leave.
 

Tonyr1084

Joined Sep 24, 2015
7,853
with it being an intermittent problem, my fear is that it tests ok while they're here and then misbehaves again after they leave.
That was exactly why it took so long to find my problem in the apartment. Power would go out and I'd call the landlord. He'd send someone to look at it but by the time his electrician got there the heater (240 VAC electric heat) would kick in and spoil the failure into "working" condition. One night it went out and I called. Left absolutely everything alone. The electrician actually removed the meter. It was only then he found (saw) the problem. It manifest itself in the dark by glowing white hot. HEY! There's an idea. Can you get your hands on a thermal camera?

Bottom line in my case - tighten up the connections. All was good after that.
 

MisterBill2

Joined Jan 23, 2018
18,176
Quite likely the neutral and the safety (green wire) ground are tied some place in your house, while the neutral in the box is through 100 feet of aluminum wire with at least 2 crimp splices. So if you suffer a bit of resistance in your local ground, which, depending on the house age may be a steel water pipe, then suddenly the return current is flowing through that lung run back to the pole. So yes, a problem in the grounded neutral in the house could lead to a wandering neutral at the entrance. Complicated indeed, but possible.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Quite likely the neutral and the safety (green wire) ground are tied some place in your house, while the neutral in the box is through 100 feet of aluminum wire with at least 2 crimp splices. So if you suffer a bit of resistance in your local ground, which, depending on the house age may be a steel water pipe,
The OP has already stated he has a single ground rod, regulation calls for two, at least 6ft apart.
Max.
 

mvas

Joined Jun 19, 2017
539
From the mast, it goes to the meter, and then from the meter straight to panel.

I thought I'd checked all I could, but I'm going to double check again in the next few days. I can't check the meter end of the wire, but I can double check the panel end of that neutral wire one more time.

The utility is planning to do a load test which is meant to verify that everything from their side up to the meter is in good shape. Of course, with it being an intermittent problem, my fear is that it tests ok while they're here and then misbehaves again after they leave.
First the root cause of this problem has nothing to do with your "Earth Grounding System" = Ground Wire, Ground Rod, Water Pipes, Ground Bond, etc
In fact, the "Earth Ground" is masking the severity of your High-Resistance Neutral Wire problem.
That is because the Earth Ground connection is in parallel with your Neutral Wire from the Pole to the Main Panel.
In your case, your Earth Ground System is actually carrying way too much Neutral Current - when in reality it should be a very, very small amount.
With Residential 240V Split-Phase and a good 3-Wire Triplex connection, you do NOT need any ground connection to have a stable 120 Volts between L1 - Neutral - L2.

Since the Voltage is inversely varying between "L1 & Neutral" and "L2 & Neutral" at the Main Panel,
the problem is in the Neutral Wire, a Neutral Crimp and/or a Neutral Screw Connection between the Main Panel, the Meter Base and/or the Pole Pig.
It is not a problem in the Branch Circuits of the House Wiring.
It is not problem with the "Earth Ground" system.

The Neutral wire connects your Neutral Bar to the Center Tap of the Pole Pig.
The Neutral Wire, from the Pole Pig, through the Meter Base, to your Main Panel,
is responsible for splitting the 240 Volt Circuit into two (2) stable branches of 120 volts each.

You said ... intermittent problem ...
Q1 - Usually 3 or 4 homes are connected to the same Pole Transformer - Do any of those homes have the same fluctuating L1-N-L2 Voltage issue? = Problem at the Pole.
Q2 - Is there a tree branch near, touching or moving your triplex wire?
Q3 - Does this only happen when it is windy? Have the utility personnel shake the triplex with their fiberglass pole to simulate windy conditions.

Have the utility loosen and re-tighten all connections inside the Meter Base.
Have an electrician loosen and re-tighten the L1-N-L2 connections in your Main Panel.
 
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Thread Starter

ebeowulf17

Joined Aug 12, 2014
3,307
First the root cause of this problem has nothing to do with your "Earth Grounding System" = Ground Wire, Ground Rod, Water Pipes, Ground Bond, etc
In fact, the "Earth Ground" is masking the severity of your High-Resistance Neutral Wire problem.
That is because the Earth Ground connection is in parallel with your Neutral Wire from the Pole to the Main Panel.
In your case, your Earth Ground System is actually carrying way too much Neutral Current - when in reality it should be a very, very small amount.
With Residential 240V Split-Phase and a good 3-Wire Triplex connection, you do NOT need any ground connection to have a stable 120 Volts between L1 - Neutral - L2.

Since the Voltage is inversely varying between "L1 & Neutral" and "L2 & Neutral" at the Main Panel,
the problem is in the Neutral Wire, a Neutral Crimp and/or a Neutral Screw Connection between the Main Panel, the Meter Base and/or the Pole Pig.
It is not a problem in the Branch Circuits of the House Wiring.
It is not problem with the "Earth Ground" system.

The Neutral wire connects your Neutral Bar to the Center Tap of the Pole Pig.
The Neutral Wire, from the Pole Pig, through the Meter Base, to your Main Panel,
is responsible for splitting the 240 Volt Circuit into two (2) stable branches of 120 volts each.

You said ... intermittent problem ...
Q1 - Usually 3 or 4 homes are connected to the same Pole Transformer - Do any of those homes have the same fluctuating L1-N-L2 Voltage issue? = Problem at the Pole.
Q2 - Is there a tree branch near, touching or moving your triplex wire?
Q3 - Does this only happen when it is windy? Have the utility personnel shake the triplex with their fiberglass pole to simulate windy conditions.

Have the utility loosen and re-tighten all connections inside the Meter Base.
Have an electrician loosen and re-tighten the L1-N-L2 connections in your Main Panel.
Thanks so much for your detailed answers! All of that sounds like what I would've thought, but this is my first time dealing with service entrance or meter related questions, so I've been looking for reassurance that I'm not loony!

Q1: The transformer is shared with three other homes, but I haven't talked with my neighbors about it, at least not yet...

Q2: Definitely no tree branches near my drop, nor the transformer.

Q3: I don't think it corresponds with wind events, but I've been meaning to pay closer attention to this possibility. Thanks for the reminder! I don't know for sure if I'll be home when the utility electrician comes back. If so, I'll ask about the fiberglass pole trick. Thanks for the tip!

As for tightening connections, I'll definitely ask the utility electrician to do that next time he's got the meter off. For the panel entrance, I'd defer to an electrician for the L1/L2 connections if I thought they needed help.

As it stands, with this appearing to be a neutral issue, I think I'll try checking the neutral connection myself. With the main breaker off (and with a meter confirming that both legs are actually off,) I feel comfortable checking and tightening the neutral connection. It would be the biggest wire I've worked with to date, but I'm not a total novice. I design, build, install, and service commercial espresso machines for a living, working with 240V circuits daily, and I rewired 2/3 of my previous house, replacing all the knob and tube circuits. (I wasn't just winging it - that job was inspected by a licensed electrician, and then by the city, and got their seal of approval.)
 
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Lo_volt

Joined Apr 3, 2014
316
I'll second mvas' suggestions. The problem is not with your ground, but with your neutral. NEC code dictates that your house should only have one connection (neutral bond) between the power neutral and ground. This is normally in the panel with the mains disconnect breaker. Your panel does not have a mains disconnect breaker, do you have a smaller box, possibly outside, that has your main breaker? It would have a single two pole breaker that would be 100, 150 or 200 amps or more.

Find where this connection exists. It may be a wire connection as mvas has suggested. It is more likely to be a bonding screw from the neutral bus bar through to the grounded panel box. It is either loose or corroded but is definitely degraded in some way.

What is likely happening is that as your expresso machine draws power, it is pulling current through this degraded (high resistance) connection causing the neutral to shift in relation to the two lines.

The problem is not likely with the transformer or the power company. They supply you with L1 and L2 and the center tap that is grounded. If your neutral is not properly bonded to the ground, it will lean to one side or the other depending on the load on each leg.

Your electrician should have figured this out right away.

See this page from Schneider Electric for a good explanation of the bonding screw.

https://www.schneider-electric.us/en/faqs/FA176082/

In case the link doesn't work:
"When a load centers is used as Service Equipment, the NEC requires that the neutral shall be bonded to the metal box. The Service Equipment is identified by the fact it includes the first disconnect of the incoming power from the Utility. For a single family house, many times the load center is the main panel, with the main breaker acting as the Service disconnect. In this panel, the green screw is used to bond (fasten) the neutral to the metal box. This is only done in the main panel. Any panels installed downstream of the main panel are called sub-panels, and the neutral in these panels must not bonded to the box."

Lastly, if you work on this yourself, be sure to turn the main breaker off while you work. You don't want to have the breaker on while the neutral is completely disconnected as the only reference to the "center" would then be through the loads on each leg, L1 and L2. You're voltage fluctuations will be far worse.
 
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mvas

Joined Jun 19, 2017
539
Your panel does not have a mains disconnect breaker, do you have a smaller box, possibly outside, that has your main breaker? It would have a single two pole breaker that would be 100, 150 or 200 amps or more.
His Main Breaker Panel does have a 200 Amp Circuit Breaker.
 
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