oldsparky52
Senior Member
- Location
- Wilmington, NC USA
I bet if I put a 40-amp load on L1-N and zero load on L2-N (properly functioning service) that you will see a voltage rise on L2 to N that will be 1/2 of the voltage drop on L1-N.
Power Company loose neutral
- Thread starter Buster2021
- Start date
- Status
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
211022-1914 EDT
oldsparky52:
You are correct for a normal application where supply line drop is the dominate factor.
For others:
If I make the measurement directly at the transformer, then the unloaded side will see a small voltage drop compared to the loaded side. This results from a small common impedance from the transformer primary.
This effect does not show up where two phases of a wye supply are derived from separate single phase transformers. But when distribution lines are included, then you are back to something like the center tapped transformer case. The problem here is that you have to combine neutral currents at 120 degrees instead of 180 degrees. In a sense the neutral wire in this case is really not a neutral wire, but it is still called that.
.
oldsparky52:
You are correct for a normal application where supply line drop is the dominate factor.
For others:
If I make the measurement directly at the transformer, then the unloaded side will see a small voltage drop compared to the loaded side. This results from a small common impedance from the transformer primary.
This effect does not show up where two phases of a wye supply are derived from separate single phase transformers. But when distribution lines are included, then you are back to something like the center tapped transformer case. The problem here is that you have to combine neutral currents at 120 degrees instead of 180 degrees. In a sense the neutral wire in this case is really not a neutral wire, but it is still called that.
.
WannabeTesla
Member
- Location
- America
- Occupation
- Licensed Electrical Contractor
My limited experience with a bad neutral was significantly fluctuating resistance between L1, L2 and the N. Obviously, amperage fluctuated simultaneously. What struck me the most was that nothing seemed to make obvious sense. My poco was excellent and they told me what they found and fixed it immediately.
MD Automation
Senior Member
- Location
- Maryland
- Occupation
- Engineer
Buster,
I agree 100% with all the advice given above. Just a quick note because I tend to worry about all sorts of things…
I am assuming you are measuring these unbalanced voltages at the main panel and it’s likely a Poco issue. You mentioned lightning strike? That could certainly compromise a neutral at a buried splice or up at a weatherhead or poletop crimp.
If you are measuring voltages at other receptacles inside the house, and the panel voltages stay balanced, then maybe an open neutral in a MWBC??
Anyway, assuming it’s a Poco neutral issue… and your Line voltages to N are swinging to 85/135 at the main with one side loaded, it’s likely this residence does not have a great bond to ground like a metallic public water pipe would offer.
So, when you load one leg with a hair dryer (toasters work well too) be aware that you may possibly energize some of the local structure / appliances and it’s possible to get a shock or tingle when touching things like faucets. This is because your service bond is weak and you are creating voltage differentials / gradients with your swinging neutral. Think dryer frame to tub faucet. Just something to be aware of, especially with people other than you in the house.
Also, any other bonds to ground like a CATV shield may start to heat up as they struggle to keep your neutral at “zero”.
So setup your hair dryer test for troubleshooting and showing a Poco lineman. But don’t leave it running longer than you need to.
Full disclosure - I am an engineer and not a real sparky. But I did stay at a Holiday Inn once
If others think this advice is misguided I am happy to be corrected.
Good luck with the job.
I agree 100% with all the advice given above. Just a quick note because I tend to worry about all sorts of things…
I am assuming you are measuring these unbalanced voltages at the main panel and it’s likely a Poco issue. You mentioned lightning strike? That could certainly compromise a neutral at a buried splice or up at a weatherhead or poletop crimp.
If you are measuring voltages at other receptacles inside the house, and the panel voltages stay balanced, then maybe an open neutral in a MWBC??
Anyway, assuming it’s a Poco neutral issue… and your Line voltages to N are swinging to 85/135 at the main with one side loaded, it’s likely this residence does not have a great bond to ground like a metallic public water pipe would offer.
So, when you load one leg with a hair dryer (toasters work well too) be aware that you may possibly energize some of the local structure / appliances and it’s possible to get a shock or tingle when touching things like faucets. This is because your service bond is weak and you are creating voltage differentials / gradients with your swinging neutral. Think dryer frame to tub faucet. Just something to be aware of, especially with people other than you in the house.
Also, any other bonds to ground like a CATV shield may start to heat up as they struggle to keep your neutral at “zero”.
So setup your hair dryer test for troubleshooting and showing a Poco lineman. But don’t leave it running longer than you need to.
Full disclosure - I am an engineer and not a real sparky. But I did stay at a Holiday Inn once
If others think this advice is misguided I am happy to be corrected.Good luck with the job.
Buster2021
DZ
- Location
- Mn
- Occupation
- Master Electrician semi retired Electrical Contractor
Yesterday I called my local POCO and insisted that they send crew out to check on their equipment at the residence. They balked and had me check on a few more items and called them back, no response. So I told them that their customer had been suffering with this problem for 13 days and It was going to end today. i kept calling different people within the POCO, then I told them that if they didn't respond I would call a power outage after hours until someone showed up. A POCO line crew showed up with the intent to finally remedy this bad Neutral problem, I was there when they cut loose the overhead triple and found the steel strands in the neutral wire the only connection left. They replaced the triplex and the POCO Bad Neutral problem is solved. The break was located up in the branches of a balsam tree not visible with binoculars. Thanks everyone on this forum for your comments. I never earned millions as a one man band electrical contractor, but I have customers that are now life long friends when you put your heart and soul in to remedying problems for them. The hours I spent at this property involved fixing many HACK installed issues besides this problem. I blame the banks and realitors for letting homeowner or handyman installations go on. I also would like to say that if buying a home or building, pay the extra money and hire a building contractor, electrical contractor, and a plumbing contractor to look the property over. I have seen the results from home inspector inspection and most aren't skilled enough to these "HACK ISSUES". I watched my daughter and son-in-law get coached by realitors twice and not follow my advise, it's Sad and guess who gets involved to fix these HACK installations. I apologize for rambling. Thanks again
Buster2021
DZ
- Location
- Mn
- Occupation
- Master Electrician semi retired Electrical Contractor
I really didn't struggle with the neutral issue, I struggled with the POCO. I tied there grounding issue down to .04 volts neutral to ground. Which is virtually zero.
Tenacity paid off.
It’s a real shame you have to basically beg someone to fix their issue though…
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Especially when this can cause fairly expensive damage claims. But that is the way of IOU POCOS these days.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I meant to add that getting a coop POCO to work with you in my experience indicates that they are almost universally timely, helpful and cooperative (oh gee a pun).
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
2110223-2007 EDT
Buster2021:
Almost the very first thing you needed to do after a few simple observations was to measure voltage somewhere and observe the change with a moderate load change. You want a 120 V load, and it can be anywhere. And somewhere, doesn't matter where, observe the 120 V supply voltage change.
Had you done this you would have immediately realized you needed to open the main panel, and measure input voltages to the panel.
With this information implying a bad neutral you then call the power company, and tell them to immediately send a crew. If they refuse, then you tell them you are calling the public service commission, and you do that.
.
Buster2021:
Almost the very first thing you needed to do after a few simple observations was to measure voltage somewhere and observe the change with a moderate load change. You want a 120 V load, and it can be anywhere. And somewhere, doesn't matter where, observe the 120 V supply voltage change.
Had you done this you would have immediately realized you needed to open the main panel, and measure input voltages to the panel.
With this information implying a bad neutral you then call the power company, and tell them to immediately send a crew. If they refuse, then you tell them you are calling the public service commission, and you do that.
.
busman
Senior Member
- Location
- Northern Virginia
- Occupation
- Master Electrician / Electrical Engineer
There is a product called the Beast (Super or Mega) that plugs into a residential meter socket and will conclusively show whether the PoCo has an issue on their side. I'd ask them if they have one.
- Status