Lost neutral, OutletLinc tried to burn my house down

[tome]

A couple weeks back we had an electrical problem that turned out to be a critter had chewed through our neutral wire at the transition of the pole to underground to our house.

I don't know if anyone has ever had this happen but it is devastating to electrical devices.  A loose/cut neutral is one of the leading causes of house fires.  When neutral is cut there can be large arcs and the full 240 VAC across the two hots swings through the lowest resistance device to ground on each leg and either shorts it or burns it open.  Then it swings to the next lowest resistance device and so on.  In our case we had a strand or two of aluminum wire on the neutral that would probably cool and reconnect for a second or two reeking havoc arcing and causing wild voltage swings.  Many devices in our house were damaged, about 40 in all.  Some are repairable, many are burnt beyond repair.  Had someone not been home to cut the main breaker our house very likely could have burnt to the ground.   I carried an APC UPS out the door on fire.  An older Ecobee EIM module went up in flames as I was shutting off breakers in a sub-panel near my furnace (one of which was burnt).  Things were buzzing, popping and flashing all over the house.  Surge protected power strips did nothing (other than burn), many devices attached to them were damaged.  There are several items that have line input fuses and I was hopeful when I found the fuse burnt but alas the fuse did not protect them.  Their circuit boards were burnt to a crisp before the fuses blew.

My one and only outletLinc (2473S) caught fire and melted in the electrical box while spewing flames up the wall (see attached pics).  The only good thing that can be said for the OutletLinc's reaction to this is that because it melted, the insulation on line and neutral wires in the box shorted and threw that circuit breaker.  In fact, after it was all over, that is the only breaker that had tripped.   My other insteon devices are surprisingly working as well as my ISY,  yay.

The last photo is of my souvenir, my neutral (on the left) and one of the two hot legs (on the right) where the squirrels did their thing.  Now it's just dealing with insurance and power company to repair and replace everything, clean carpets and drapes to try to get rid of the burnt electrical smell throughout the house.  It is many many thousands of damage.  

Don't underestimate the squirrel!

-Tom

[larryllix]

Geeezzzz! Make sure the house is aired out well. Many of those plastics can be carcinogens when they burn!!

 

Nasty stuff. The ground system should have carried the neutral somewhat except for heavy loads on one leg. Check if the strap around the water meter was removed at some point. In my career we found neutral that were never hooked up for several years of operation. This depends on how good your earth conducts too.

[paulbates]

Wow!

I had a chipmunk chew through one of the 24VAC lines to a sprinkler system mastervalve. That killed the the ezflora zone that powered it... which had survived many years lighting strikes before that. 

Paul

[apostolakisl]

Crazy.  How does a chipmunk chew through the main neutral?  That is like the size of my thumb.  I guess the hot 120 legs were sending power "backwards" through things on the other leg?  Lucky no one got hurt.  Theoretically, all of the "grounded" things in your house would have been hot since it seems your ground didn't seem like it worked either.

[mwester]

Industrial equipment commonly has over and under voltage protection, as well as missing-phase protection... I wonder how much a mass-produced main breaker with protection from this type of fault might cost?  (Just guessing it would be a couple orders of magnitude cheaper than the damage...)

[xKing]

18 minutes ago, mwester said:

Industrial equipment commonly has over and under voltage protection, as well as missing-phase protection... I wonder how much a mass-produced main breaker with protection from this type of fault might cost?  (Just guessing it would be a couple orders of magnitude cheaper than the damage...)

$55, it trips if voltage > 165V

[tome]

My boiler has a lockout circuit that when it senses a low/over voltage situation it just shuts off for 5 mins.  It then wakes up, checks voltage, and then either allows you to turn it back on or goes back to sleep.  When the power company restored power I went to turn it on first as it is my primary source of heat (it was 20 degrees the 24 hours I was without power).  I forgot about this feature.  I immediately called my HVAC contractor and they reminded me of the lockout.  Sure enough a couple minutes later it was happy, it faired well in all this.  I wish all my major appliances had that feature!!!!!

I wonder too how much a protected breaker panel would be.  I haven't ever seen one.  I have thought I should get a whole house backup generator (I have a plug in type when I need it) and an automated transfer switch on a backup generator might have saved me too (not 100% sure about that but seems likely).

Yeah, why do critters want to chew insulation and aluminum?  Bizarre.  They chewed a significant amount of insulation off all the wires running from the ground to the transformer on the top of the pole.  The repair guy had to take all the conduit off the pole and wrap and repair the wires from the ground up in many places.  See pic below for one section of hot that was missing most of it's insulation.  Surprising that we hadn't had a short before this.

My ground connection is quite good, a very large gauge (not sure exactly) bare copper wire running only a couple feet to a rod planted in the ground outside.   The electrical entry and panel is in a basement wall very close to the physical ground outside.

[apostolakisl]

I may be wrong on this, but I would expect a high quality ground would have been the path of least resistance for each leg of the 120.  That would have allowed your electricity to work like normal even without your neutral line to the city pole.  

But for sure, if you were running 120v devices using the other leg as your "neutral", then your ground would have been "charged".  There is no way for electricity to "push" its way across to the other leg without a charged neutral (and thus a charged ground since they are connected at the panel).

[larryllix]

I may be wrong on this, but I would expect a high quality ground would have been the path of least resistance for each leg of the 120.  That would have allowed your electricity to work like normal even without your neutral line to the city pole.  

But for sure, if you were running 120v devices using the other leg as your "neutral", then your ground would have been "charged".  There is no way for electricity to "push" its way across to the other leg without a charged neutral (and thus a charged ground since they are connected at the panel).

Definitely! I would expect past or future lightning problems with electronics in that home.

 

A good electrician should be able to improve the grounding for the house by adding a second ground rod. One ground rod doesn't pass code here anymore. With proper test equipment the ground resistance can be tested.

 

OTOH a single grounding plate will? I guess the contact area are us what it's all about.

 

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[xKing]

Common misconception, grounding won't do a thing in open neutral case.

[apostolakisl]

5 minutes ago, xKing said:

Common misconception, grounding won't do a thing in open neutral case.

If the open neutral is between the panel and the city, how would it not (vs the open neutral being between the panel and the end device)? 

[tome]

16 minutes ago, xKing said:

Common misconception, grounding won't do a thing in open neutral case.

He is absolutely correct.  See: https://www.ecmweb.com/content/open-service-neutrals

By the way, since 2005 (or 2008, I forget when it went from bedrooms to all areas of occupancy) AFCI breakers are recommended (required?) in new construction.  My house was built in 2000, there are no AFCI breakers at all.  These would have helped immensely and lost neutral is one of the main reasons they are employed.

-Tom

 

[apostolakisl]

1 hour ago, tome said:

He is absolutely correct.  See: https://www.ecmweb.com/content/open-service-neutrals

By the way, since 2005 (or 2008, I forget when it went from bedrooms to all areas of occupancy) AFCI breakers are recommended (required?) in new construction.  My house was built in 2000, there are no AFCI breakers at all.  These would have helped immensely and lost neutral is one of the main reasons they are employed.

-Tom

 

I think this is saying the same thing I am saying.  "Grounding the grounded (neutral) conductor to the earth shunts potentially dangerous energy from the system into the earth [250.4(A)(1)]."

An open neutral (at the utility) energizes the entire ground in your house since ground and neutral are bonded at the panel.  If you have a highly efficient ground, then you should see essentially all the potential unload itself into the Earth and close the loop back to the power companies ground (at the sub-station).  A perfect ground would be indistinguishable from a utility provided neutral.  The better your ground, the less potential you will get in your homes ground with an open utility neutral.  Having the neutral/ground charged will make the potential across your devices (the voltage) be lower than 120 damaging the equipment, and also everything connected to ground will be charged and potentially electrocute you should you touch it while connected to a good ground.  If your ground is the city water system, I bet you barely have any issues at all with an open neutral.  If it is a rod in the ground, probably you do have issues. 

 

EDIT:  Also, it would depend on how balanced your power consumption is at the moment between the two legs.  If you were drawing the exact same current from each leg, then everything would zero out on the neutral/ground side.  The city neutral isn't doing anything when pulling the same current on each leg of the 120v.  

 

EDIT AGAIN: I can't think of what the reason for a grounding rod outside your house if it isn't for saving your but on an open city neutral.  Would there be something special or better about a grounding rod outside your house in the event of a lightening strike?  Probably since utility ground would be at a different location and lightening potential in Earth changes a lot with distance from stike.

[larryllix]

I think this is saying the same thing I am saying.  "Grounding the grounded (neutral) conductor to the earth shunts potentially dangerous energy from the system into the earth [250.4(A)(1)]."
An open neutral (at the utility) energizes the entire ground in your house since ground and neutral are bonded at the panel.  If you have a highly efficient ground, then you should see essentially all the potential unload itself into the Earth and close the loop back to the power companies ground (at the sub-station).  A perfect ground would be indistinguishable from a utility provided neutral.  The better your ground, the less potential you will get in your homes ground with an open utility neutral.  Having the neutral/ground charged will make the potential across your devices (the voltage) be lower than 120 damaging the equipment, and also everything connected to ground will be charged and potentially electrocute you should you touch it while connected to a good ground.  If your ground is the city water system, I bet you barely have any issues at all with an open neutral.  If it is a rod in the ground, probably you do have issues. 
 
EDIT:  Also, it would depend on how balanced your power consumption is at the moment between the two legs.  If you were drawing the exact same current from each leg, then everything would zero out on the neutral/ground side.  The city neutral isn't doing anything when pulling the same current on each leg of the 120v.  
 
EDIT AGAIN: I can't think of what the reason for a grounding rod outside your house if it isn't for saving your but on an open city neutral.  Would there be something special or better about a grounding rod outside your house in the event of a lightening strike?  Probably since utility ground would be at a different location and lightening potential in Earth changes a lot with distance from stike.

We have had houses connected without neutrals running for years before we found the electrician's mistake. It all depends on the dirt between the house and transformer.

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[apostolakisl]

6 minutes ago, larryllix said:

We have had houses connected without neutrals running for years before we found the electrician's mistake. It all depends on the dirt between the house and transformer.

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How did you come across this?  Just curious.

EDIT: And what kind of ground did they have?  City water system or a rod stuck in the ground or what?

[tome]

That is a different problem, if I am understanding what you are saying.  The root of the problem I had isn't that the house wiring has no neutral, it is more that the secondary of the transformer on the pole has lost it's neutral ground reference.  If a house electrician doesn't wire up the neutral, but the neutral coming from the transformer on the pole is connected to a grounding rod (say, at or near the meter) than not so big a deal.  Without a ground reference on the secondary side neutral voltage can swing unpredictably between phases based on loads and also based on capacitive coupling with the primary side.  That is what happened in my case.

-Tom

 

[apostolakisl]

32 minutes ago, tome said:

That is a different problem, if I am understanding what you are saying.  The root of the problem I had isn't that the house wiring has no neutral, it is more that the secondary of the transformer on the pole has lost it's neutral ground reference.  If a house electrician doesn't wire up the neutral, but the neutral coming from the transformer on the pole is connected to a grounding rod (say, at or near the meter) than not so big a deal.  Without a ground reference on the secondary side neutral voltage can swing unpredictably between phases based on loads and also based on capacitive coupling with the primary side.  That is what happened in my case.

-Tom

 

Not really following you.  The transformer output neutral at the top of the pole is bonded to 1) city neutral, 2) pole ground wire, 3) neutral to your house. So if you lost your poles grounding wire, it wouldn't be a big deal since the neutral running from pole to pole down the street has a lots of grounds, one at every other pole in the neighborhood, plus the one at your service panel which is also bonded to that same neutral.

[larryllix]

That is a different problem, if I am understanding what you are saying.  The root of the problem I had isn't that the house wiring has no neutral, it is more that the secondary of the transformer on the pole has lost it's neutral ground reference.  If a house electrician doesn't wire up the neutral, but the neutral coming from the transformer on the pole is connected to a grounding rod (say, at or near the meter) than not so big a deal.  Without a ground reference on the secondary side neutral voltage can swing unpredictably between phases based on loads and also based on capacitive coupling with the primary side.  That is what happened in my case.
-Tom
 

The transformer on the street has a ground connection on the neutral right at the secondary neutral bushing X0. This prevent high voltage leaking from the primary into the secondary.

The house now ties the neutral to ground at it's location to ensure the occupants don't have different appliance voltages than their feet.

The two grounds should carry some or all the neutral current between neutral connections but it is not supposed to be needed to do that. It may, with good earth materials but may not. It should have limited the voltage swing on the phases but at no time can they exceed the phase to phase 240vac between them or to the neutral.

According to the description it sounds like the transformer grounding is defective also and some primary leakage got into the house between the phases and the local grounding conductors. This may imply a claim on the utility would be in order and successful.

The home grounding may have been carrying the whole neighborhood grounding and when lost, things went wild with primary voltage leak through.

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[ELA]

apostolakisl

,

 Most soils are not that good of a conductor.     What are you thinking the resistance would be from a house ground rod to the transformer ground  ( say 100ft away) under the open neutral situation?    Assuming no bonded metal water line.

Compare that to the resistance of each leg of the service with a 20amp load on each leg.

 

[apostolakisl]

2 hours ago, ELA said:

apostolakisl

,

 Most soils are not that good of a conductor.     What are you thinking the resistance would be from a house ground rod to the transformer ground  ( say 100ft away) under the open neutral situation?    Assuming no bonded metal water line.

Compare that to the resistance of each leg of the service with a 20amp load on each leg.

 

Then why bother?

[larryllix]

Then why bother?

The ground tied to your neutral in your house is to keep your feet at the same potential as the electrical service.

This prevents any voltage rise in the electrical system from creating a difference potential across insulation in appliances and possibly your body. It also backs up the grid grounding somewhat.

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[apostolakisl]

5 hours ago, larryllix said:

The ground tied to your neutral in your house is to keep your feet at the same potential as the electrical service.

This prevents any voltage rise in the electrical system from creating a difference potential across insulation in appliances and possibly your body. It also backs up the grid grounding somewhat.

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I know.  "why bother" is directed at ELA's comment.  He is implying that dirt isn't capable of zeroing out a charged house ground.  If it isn't, then what is the point.  If your house ground is charged, there is nothing that will save your *** if your body completes the circuit.  Circuit breakers and GFCI's won't do anything.  

[larryllix]

I know.  "why bother" is directed at ELA's comment.  He is implying that dirt isn't capable of zeroing out a charged house ground.  If it isn't, then what is the point.  If your house ground is charged, there is nothing that will save your *** if your body completes the circuit.  Circuit breakers and GFCI's won't do anything.  

Not many people can reach from the 'charged' house ground to the transformer ground.

As long as all point of reach are at the same equipotential there is no danger

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[apostolakisl]

1 minute ago, larryllix said:

Not many people can reach from the 'charged' house ground to the transformer ground.

As long as all point of reach are at the same equipotential there is no danger

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You don't have to touch the transformer, just something with a better connection to it than your crappy grounding rod.

[larryllix]

5 hours ago, apostolakisl said:

You don't have to touch the transformer, just something with a better connection to it than your crappy grounding rod.

I guess I am not understanding the confusion. Systems are grounded to keep the ground at the same potential as the neutral of the system at each location where it is grounded.

eg. A dry wood pole has a cracked insulator on the high voltage and a small current leaks to the wood pole. But due to the poles' dry wood and high resistance no protection is tripped. Now the pole has a voltage gradient down  the length of the pole as the voltage decreases with length. A  person leans against the pole and gets electrocuted between their hand against the pole and the ground about 18" away from the pole. A ground wire running down the pole and tacked frequently can help keep the voltage  gradient all at the same potential down the pole, eliminating this (mostly). However the gradient jump is moved, and sometimes focused into another place as it escapes back to the transformer neutral ground further away and can cause problems for somebody else.

Equi-potential grounding doesn't really care what the potential of the wiring is, as long as the ground around it is at the same potential. Think Faraday cage for your house.  Also think to connect your earth to your electrical system. There is no absolute ground.

OTOH: When we had problems with farm have step gradients, this is caused by grounded neutral in the rural.  At the huge transformer station the neutral on 3 phase 4 wire systems is grounded at the transformer. Now think about a 44kV system transmitting power across a country...say 40 miles. Any neutral current causes a voltage drop in the neutral conductor. On a higher voltage system  a few hundred volts is common and not a big deal to a 44kV voltage system. Now tie the customer end neutral to ground at the transformer primary and you have a few hundred volts across the ground in the county. In places where the ground is not a good conductor this can focus  into smaller distances, like between your water system and the ground. Cows get a poke in the mouth and will never drink there again. They will drop dead from thirst. People get shocks in the shower between the shower head water and the metal bathtub.
The answer?
    Unground the neutral at the far ends of transmission lines. It can cause other dangerous problems though.  Most rules disallow two grounds on any conductor. Utilities ignore that idea.
    Make a Faraday cage around the farm with a series of grounding rods completely surrounding the farm. Problem solved! Now the problem moves to the next farm!
   These problems didn't happen in older systems (think Telsa  )when we only transmitted 3 phase 3 wire floating delta systems with no grounding. Then you get insulation breakdown from floating phases with higher voltages to ground than the insulation of the system can handle.

 

Oh Gawd! I'm back at work again!