Everything in the house is acting up. The fridge has melted ice, the radio is acting strange, etc.

I multimetered the panel box and each breaker is either 90 V or 140 V alternately. I have a plan to upgrade the box from 100 A to 200 A as the meter shows the system is set for 200 A. But meanwhile everything is acting up.

  • My guess is you are in the US. Or possibly Brazil or Japan? Commented Oct 23, 2018 at 8:25
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    Hey, can you give us an update on how this issue turned out? Commented Jan 7, 2020 at 20:21

7 Answers 7


Call the power company NOW and report a power outage

The fact that you've worked on your panel is unrelated. Given the testing you just did and the results you got -- you have a power outage at the meter pan or before. It could be where the neutral service wire connects to your neutral bar, but that's the only place it could be on your side, and super easy to check.

To be more precise, the type of outage is a "Lost Neutral".

Loss of a supply wire at or before the meter pan is a power outage.

If the dead supply wire is a hot, half your panel will work. If the dead supply wire is a neutral, your 240V loads will work and your 120V loads will have scary weird voltages on them.

It's still a power outage and should be treated as such.

As long as you are confident in the quality of the connection between your neutral service wire and your neutral bus, you should button up the panel and there's no reason to show it to the power company. Everything they'll care about will be at the meter pan or their side of it.

DON'T procrastinate this or try to work around it by balancing loads etc.

Seriously, unless you plan to shimmy up a pole with a set of Allen sockets, every possible path ends with you calling the power company and them fixing their service-drop issue. Which they will do for free, same-day and probably 10 minutes up on the pole. And then you'll be like "darn it Harper, why didn't you lead with 'Call the power company', why send me in circles doing all that other stuff first?"

  • I appreciate the detail. Ill show this to the electrician if I can get one over here. Yes I have some differing voltages on different outlets. Just hope I can keep the hot water heater stable. The fridge is goes from making ice to melting ice and the dishwasher im afraid is fried.
    – drmadef
    Commented Oct 19, 2018 at 22:53
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    @drmadef it's your time, but don't wait for the electrician, just call the power company now. This is an emergency. As far as the hot water, if it is a 240V-ONLY device (no neutral) it is safe to power it. Every other breaker must be OFF and never turned back on until the PoCo gives the all clear. Ignore my advice, but your electrician will just tell you "call the PoCo" and then you'll just have waited unnecessarily and be $50 poorer. You do understand the PoCo visit is free and typically same-day. Commented Oct 20, 2018 at 0:35

You should call the utility company. You likely have an open circuit between the neutral bus bar on your electric panel and the neutral wire that goes to the meter, or further upstream. Split-phase power usually works like this in the USA and Canada:Split-phase power

The transformer's secondary is 220V-240V, and it is tapped in the middle to produce 120V between the center tap and any of the two ends. Connecting between the red and black phases gives you 220V-240V. Connecting between a red or black wire and the white gives you 110V-120V. The neutral wire (white) is grounded at the box or at the utility's equipment, so there should never ever be voltage on a neutral wire.

Good? Now, you say one side of the panel box (say the red) has 90V and the other side has 140V. 90+140 = 230, so it looks like the black and red hot wires are connected correctly. However, the neutral wire seems disconnected at the meter or between the meter and the transformer. This is very bad for several reasons:

Normally, with a neutral that is connected correctly at the transformer, you have 120V between line and neutral regardless of current in each device: Good neutral

In your case, however, there seems to be no neutral connection at the transformer, so you now have two circuits in series on a 230V supply:Bad neutral

If the lamp and TV are on, this will work fine because they consume the same current and will split the 230V 50/50, so you decide not to call an electrician.

  • Now, you decide to turn off the lamp, and the TV no longer works (it has no neutral, so its current return path was through the lamp).
  • The fridge compressor starts, so now you have a 800W load on one side and a 100W load on the other side. From the 100W load's point of view, the 800W load is a dead short and therefore the TV receives about 200V. Kaboom!
  • After the TV has melted and burned, there is now an open circuit, so the fridge and the lamp turn off. You go to the closet and grab a bulb. You turn off the switch to change the bulb safely, but you still get electrocuted, because switches only switch the hot side of a circuit, not the neutral. So the current flows from the transformer, through the fridge, through the threads on the light bulb socket, through your heart, then to the ground via the metal ladder. Even if you turned off the breaker for the lamp, the breaker for the fridge is still on and you still get electrocuted.

You cannot do this repair safely, because the broken conductor is most likely located upstream from the main breaker, and therefore someone from the utility will have to remove the meter from the sealed enclosure to diagnose the fault safely. In the meantime, turn off the main breaker, as this is a dangerous situation.

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    I need a lot more studying after following your graphics. Thanks so much and hope to understand this better. I suppose I have no more options but to call the power co. Its not that I dont appreciate codes and standards to keep the neighborhood from looking like Bangladesh but contractors love it when someone calls them without understanding the issue. I'm going solar if I survive this episode as I dont have good experiences with the power authorities.
    – drmadef
    Commented Oct 19, 2018 at 23:04
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    @drmadef This is something that the utility company should fix for free. The fault is in their equipment, not yours, and it's a major safety hazard.
    – zwol
    Commented Oct 20, 2018 at 14:40
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    @drmadef: By substituting solar with the utility, you are increasing the scope of responsibility by adding your own power plant, electrical storage plant, transmission system, and sporadic generation characteristics which might well cause you to add a generator or other devices. Plus the distribution system you have now. I fully support doing so, but it will not be making your system simpler.
    – wallyk
    Commented Oct 21, 2018 at 1:56

It sounds like either the transformer feeding your house has an issue, or the neutral is broken. It seems like a local issue since the average of the two legs is 115V, which is a normal voltage in North America. You should throw your main and call the power company.

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    Thanks Ben. Sound advice in a normal situation. I am reluctant to get the power company involved as I did all the work myself and have not had the (pleasure) of an inspector to check my work. Cannot take the chance the he/she would get pompous and shut off my power as ive not yet passed the homeowner-contractor test. I have the code book and im not careless when doing work. Ill wait to see if I can get the journeyman out here.
    – drmadef
    Commented Oct 19, 2018 at 19:20
  • Does each house in the neighborhood have its own transformer? and if not would my neighbor be experiencing the same thing?
    – drmadef
    Commented Oct 19, 2018 at 19:28
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    If it's the transformer, yes other people would have the same problem. The number of people that can pull from it will depend on the transformer. To test the neutral, you could measure from neutral to ground and see what the voltage difference is. The problem with that is there is could be a normal voltage difference since the ground and neutral are grounded at different points.
    – Ben
    Commented Oct 19, 2018 at 20:31
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    If there's something wrong with the neutral connection between your house and the transformer, then only your house would be affected. Commented Oct 19, 2018 at 20:41

Sounds like you have a bad neutral. You need to turn off the power until it is found and rectified.

  • Thanks Peter. Can you give me some technique on troubleshooting the "bad" neutral? Can I run a continuity check from the neutral bar on the box, going outlet to outlet to check which neutral? I have a 50' line on my continuity light so I can do that to each plug outlet in the house. The lights dont have any problems as I was careful to not set them up on the same breaker. Ive had no issues for 3 years since I wired the house. Just happened for no (appearant) reason. Cant get an electrician for days but im very careful and know how to check things with instruction.
    – drmadef
    Commented Oct 19, 2018 at 19:00
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    I'm not an american or an electrican but I understand you have removable meters that are plugged into a base, if that is the case I would think the next step would be to unplug the meter, then make voltage measurements on the input side of the meter base and continuity measurements from the output side of the meter base to the panel. I would also visually inspect the meter base itself. Commented Oct 19, 2018 at 19:18
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    @PeterGreen Pulling the meter is NOT a good idea. Not sure if it is against the law, but definitely against utility company policy. And unless you are 100% certain of what you are doing, potentially very dangerous. Visual inspection is as far as it goes - look but don't touch unless you REALLY know what you are doing and (preferably) have utility authorization. Commented Oct 19, 2018 at 20:31
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    DO NOT TRY TO PULL YOUR OWN METER. You have a main disconnect, it might be right near the meter, it might be the main breaker in your main panel. Turn that off and call the power company. Commented Oct 19, 2018 at 20:39
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    Your lights don't have any problem because you smartly used CFL or LED lights, and their electronic drivers are multivoltage, will work on 90-264V and are riding through this outage by drawing more or less current as needed to hit their target wattage. Commented Oct 19, 2018 at 21:06

I think it would actually be best to turn off your main breaker or open your main disconnect first, THEN turn off all the other breakers until the problem is fixed and power is restored.

Then call the power company, or an electrician if you can get a faster response.

When the problem is fixed, turn on the main first, then turn on the branch circuit breakers (after verifying voltages if possible).

With an open service neutral you'll see the voltage change on 120V circuits - circuits on the more heavily loaded leg will fall, circuits on the less heavily loaded leg will rise by the same amount - they'll still add up to about 240V or so (whatever your actual line to line voltage is).

For this reason, if you start turning off branch circuit breakers off you may very well make the imbalance worse and do more damage to your electronics etc.

It's also a little safer to close your main with the branch circuit breakers open, then close the branch circuit breakers.

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    I see what your saying about the sequence of breakers on/off vs turning the main off first. I may have already fried the dishwasher. I may have no choice but to call the power co.
    – drmadef
    Commented Oct 19, 2018 at 22:54

Tell the electrician that you've been told that you have a lost neutral. He should know how to test for that. You said that you had 90 v at some receptacles and 140 V at others. This was with some loads connected. This is diagnostic for a lost neutral.

With a lost neutral if all loads are off you will measure the same voltage at all 120 V circuits (hot to neutral or hot to ground). If you add a load on one receptacle, then voltage on the hot for that receptacle (and the voltage on any hot on that entire leg) will be lower than 120 V. And on the other leg voltage on any 120 V hot (measured to neutral) will be higher than 120 V by the same amount as it was lower on the loaded leg. A good load is a hair dryer or a vacuum cleaner or an electric space heater.

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    Could you summarize what the electrician told you? Commented Oct 25, 2018 at 0:03
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    Hi again. The electrician didn't check for the open neutral but quoted me a price to pull the ticket, install a new 200 panel, and to attach everything, then have the power co move the incoming line and increase the size of the line.
    – drmadef
    Commented Oct 25, 2018 at 16:57
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    He made it clear that my work although functional (before the lost neutral) wasn't code. I would have preferred an absolute of where the open neutral was. My question to you is how can I confirm that the open neutral is somewhere After the service meter, in other words, something I can deal with. If however it's in the meter or before the service there's nothing I can do and have to accept whatever the power co says. Is it simply a continuity check of the neutral from the meter to my box? Because if so I have to increase the size of those anyway.
    – drmadef
    Commented Oct 25, 2018 at 17:06
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    ... And I did your suggested load test using my toaster and yes it did imbalance the V on L1 90 and L2 140 so it's for sure an open neutral.
    – drmadef
    Commented Oct 25, 2018 at 17:11
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    And which leg was the toaster on? The only thing for you to do is to call the power company. They will know how to determine whether the fault is in their system and will fix it if it is. I do not believe that they are not going to report you to code enforcement. You are wasting time and damaging your appliances by delaying calling the power company. Commented Oct 25, 2018 at 22:20

I have learned a lot from all the answers, and it may be that what my point here is so obvious that it doesn't bear mentioning, but it was not obvious to me and the same may be true for some others.

It seems to me that the effect of the grounding (earthing) paths has not been attributed as the cause of the damaging voltage rise on one leg due to a lost neutral.

Evidently in the US we use the TN-C-S grounding system. See https://en.wikipedia.org/wiki/Earthing_system for which a broken neutral is a major safety risk.

If the neutral is lost (completely or partially) the only or main return current path from the panel (ground rods) to the transformer (ground rod) is through the earth, a path which has significant resistance (unlike an intact neutral which has effectively zero resistance).

For the 125 V power draws in the house, the current flow back to the transformer is the difference between the current in the two hot legs. An imbalance in the two legs will appear as a non-zero current in the return path. If the low resistance neutral is lost, this current will cause a voltage difference (V = IR) between the ground rods at the consumer panel and at the transformer. This voltage difference will be subtracted from the voltage of one leg in the house (the higher loaded one), but added to the voltage at the other leg (the lower loaded leg). Hence any equipment on the lower loaded leg will get higher than half the voltage difference between the legs. And there could be a cascading failure because every time a load disappears (as equipment fails) on the higher voltage leg the voltage gets that much higher.


I played around with the infinite grid of resistors model of the path from the house ground rod to the ground rod at the transformer pole and got stumped and humiliated pretty fast. @Harper referred to this in his comment.

Googled it and found a nifty answer https://www.mathpages.com/home/kmath669/kmath669.htm(The answer for the problem set in the cartoon in @Harper 's comment would be -0.5 + 4/pi = 0.773 Ohm.)

This mathpage analysis gives the formula for the resistance between two points on a diagonal separated by m diagonal steps as:

Rmm = R(2/pi)(1 + 1/3 + 1/5 + 1/7 + . . . + 1/(2m-1))

I guess one could estimate the resistance per foot of the soil and then the number of ft to the pole would be m. But my takeaway is there is significant resistance between the ground rod of the house and that of the transformer pole.

I have two ground rods in series and I could disconnect the outer one from my panel and using jumper cables and an extension cord measure the resistance. Not sure I'll be able to motivate myself to do this though. Does anybody know the resistance through 30 ft of "soil" (now very wet Dallas soil)?

EDIT2 I now realize that I would have to disconnect both ground rods to get an accurate measurement and I am not willing to do that. In my yard away from the house I could stab two scrap pieces of cut-off grounding rod and see what resistance I get between them.


I did go out and pound two 18" long pieces of grounding rod 1 ft into the ground 30 ft apart in our very wet backyard. I used a 50' extension cord as an extension of the test leads of my new Fluke 115 true rms multmeter in the resistance mode. Of course, this is a DC measurement and quantitatively meaningless but I'm just reporting what I got. Someone here must know what a valid result should be.

The first value that appeared on the display was ~ 40 ohm and this rose over ~10 seconds to ~ 120 ohm. I can see that a DC ohmmeter is not going to give results meaningful for 60 hz ac, but I'm just reporting what I got. I would guess ~ 2 ohm to 20 ohm impedance for 60 hz.

EDIT4 The resistance along a diagonal in a 2-D infinite grid of resistors R was referenced above

Rmm = R(2/pi)(1 + 1/3 + 1/5 + 1/7 + . . . + 1/(2m-1)).

The sum of the reciprocals of the odd integers (aka the odd harmonic series) does not converge as m increases to larger and larger m. For m > 5 and progressively better for m > 10 the sum of this series asymptotically approaches a logarithmic function

gamma/2 + Ln(2) + (1/2)Ln(m), where gamma is the Euler (or Euler-Mascheroni) constant ~ 0.57722, so

0.57722 / 2 + 0.69315 + (1/2)Ln(m) = 0.98176 + (1/2)Ln(m).

Testing this for m = 7

The sum gives: 1 + 1/3 + 1/5 + 1/7 + 1/9 + 1/11 + 1/13 = 1.9551

The logarithmic formula gives 0.98176 + 0.5 Ln(7) = 0.98176 + 0.97296 = 1.9547, and the logarithmic formula gets closer and closer as m >.

So the resistance along a diagonal of m diagonal steps is approximated by

Rmm = ~ R/pi (1.9635 + Ln(m)) where m would be the number of diagonal steps between the two nodes.

So we can see that the resistance between the ground rod of a house and the ground rod of the transformer is a logarithmic increasing function of the distance. This means it is a very slowly increasing function of the distance.

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    Yes, that is the underlying mechanism, and yes, it is indeed "electrifying all the grounds in the house". The latter is usually not an issue because people usually shut off power and fix the lost neutral immediately. Commented Oct 20, 2018 at 0:59
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    And since the neutral and ground are bonded in the panel, electrifying all the neutrals. So with a lost neutral should one be able to measure a voltage equal to 1/2 the difference between the legs from a neutral in an outside receptacle on the other side of the house from the meter and a rebar stuck into wet ground? Commented Oct 20, 2018 at 1:50
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    Yes, if the rebar is far enough away from the ground rod / route to transformer not to be affected by it. Commented Oct 20, 2018 at 3:25
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    To be more specific, the house's ground rod is pulling the soil away from zero volts. The transformer ground rod is at 0 volts. Have you ever seen an open-frame rheostat or large adjustable resistor? When it's running it has 2 voltages on opposite ends, and you change the voltage you get by moving the wiper or clamp up and down the resistor. The soil is like that resistor, it's a planar resistor (actually 3-D). Obligatory XKCD... Commented Oct 20, 2018 at 18:22
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    With the Edison three wire service, the 120V circuits are L1-N or L2-N. With the service neutral missing, all 120V circuits turn into a L1-N-L2 series-parallel 240V circuit. All the L1-N circuit loads are in parallel, and all the N-L2 circuits are in parallel, and the two parallel circuits are in series. The voltage from L1-N and N-L2 must of course add up to 240. The voltage drop across each of the loads in the series circuit is proportional to the load; the voltage on the more heavily loaded circuit will be higher. Commented Oct 21, 2018 at 11:23

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