Open Neutral Identification

[fant]

How does the NEC address maintenance of the neutral circuit? When neutral feed (return path to transformer) fails, the customer's entire ground circuit becomes a sacrificial anode, life safety issue, and fire hazard. I can find nothing that addresses a failure (or verification the system is working) of the Neutral system within NEC.

The need to answer to this question becomes more relevant when a tradesperson is electrocuted when working on pipes.

 

[iwire]

I do not know of any code or standard requiring open neutral protection or monitoring.

 

[user 100]

How does the NEC address maintenance of the neutral circuit? When neutral feed (return path to transformer) fails, the customer's entire ground circuit becomes a sacrificial anode, life safety issue, and fire hazard. I can find nothing that addresses a failure (or verification the system is working) of the Neutral system within NEC.

The need to answer to this question becomes more relevant when a tradesperson is electrocuted when working on pipes.

As said above there is no requirement for monitoring the health of the svc neutral. Also, the issue of shock/electrocution can be looked at another way- the NEC does require the bonding of metal pipes in 250, effectively reducing the risk anyway- better to have the pipe bonded than not.

Hope this doesn't turn into another discussion about why bonding pipes is a bad idea.:happysad:

 

[don_resqcapt19]

I am not aware of a device on the market that is designed to detect an open neutral.

 

[fant]

Problem defined

Problem defined

As said above there is no requirement for monitoring the health of the svc neutral. Also, the issue of shock/electrocution can be looked at another way- the NEC does require the bonding of metal pipes in 250, effectively reducing the risk anyway- better to have the pipe bonded than not.

Hope this doesn't turn into another discussion about why bonding pipes is a bad idea.:happysad:

Unfortunately, most big businesses have to be required by law to do the right thing, especially if time or money is involved. Since there is no NEC requirement to maintain (or even periodically check) the health of the svc neutral, some power companies wait for a catastrophic event to have the customer inform them of their problem.

Bonding pipes to the svc neutral was never intended to bypass current returning to the transformer (because of an open neutral between the secondary and the transformer), but that situation has developed and the result is copper water pipes and natural gas lines remaining energized for years until they begin to leak. Another other unfortunate impact of pipes leaking under a foundation is how the repair costs are disallowed by insurance companies. Not only is the customer put in danger of electrocution, but is also forced to cover all damages.

The pipe bonding is designed to provide life safety. An open Neutral svc cancels that life safety and also keeps GFCI from operating. Shouldn't a problem be corrected by the owner of the problem?

 

[user 100]

Unfortunately, most big businesses have to be required by law to do the right thing, especially if time or money is involved. Since there is no NEC requirement to maintain (or even periodically check) the health of the svc neutral, some power companies wait for a catastrophic event to have the customer inform them of their problem.

Bonding pipes to the svc neutral was never intended to bypass current returning to the transformer (because of an open neutral between the secondary and the transformer), but that situation has developed and the result is copper water pipes and natural gas lines remaining energized for years until they begin to leak. Another other unfortunate impact of pipes leaking under a foundation is how the repair costs are disallowed by insurance companies. Not only is the customer put in danger of electrocution, but is also forced to cover all damages.

The pipe bonding is designed to provide life safety. An open Neutral svc cancels that life safety and also keeps GFCI from operating. Shouldn't a problem be corrected by the owner of the problem?

So we should just leave everything floating?:happyno:

You know, many utilities do pay in the advent that something on their end causes a customers equipment to be fried. And how many customers are going to like another fee to pay for the added millions in yearly testing to be done by the utilities? And if the issue is on te customer end, why should utilities be responsible?

About the gfci- the 240v from a lost neutral would likely ruin the device and smoke a lot of other 120v equipment, but if you had the back up neutral thru the common city water main/wp gec connection between neighbors......

 

[fant]

Thanks

Thanks

I am not aware of a device on the market that is designed to detect an open neutral.

I am not aware of a device on the market that is designed to detect an open neutral.

An open svc neutral to my home, unknown for 7-10 years, resulted in turning my plumbing into a sacrificial anode for the power company and thinning copper plumbing under the foundation that created pinholes in 15 year old copper pipes. With leaks wetting the soil around the electrified pipes, the current created more pitting and a type of electrolosis. Water slowly began flowing up through the slab into the house and ruining floors. Since the source of the water damage was under the foundation, insurance denies coverage for damage. The damaged pipes that flooded the home were pitted by continual (for years) current flow that I was contracting (paying) to return on the svc neutral. Damage to my home is the result of no one checking the health of the svc neutral - ignored maintenance. The discovery of electrified copper pipes under my home was made by a plumber, who almost lost his life in muddy tunnels grabbing copper pipes with at least 89 volts. My natural gas system was also carrying close to 90 volts for years - NEC requires all metal under the slab to be bonded to ground and ground bounded to neutral in the svc mains. NEC never intended for earth ground to replace the svc neutral, especially for years at a time. Momentary assistance is the exception to existing at zero volts. NEC assumes that svc neutral will always work perfectly and the power companies will maintain svc neutral circuit reliability.

The result is a stalemate with consumers loosing vast sums of money repairing damage caused by the power company (as well as people killed in mysterious natural gas explosions) and most people never understanding the scope of the problem and insurance companies helping the power companies hide the source of the problem. This is why I'm trying to get a simple line added to NEC that requires periodic circuit reliability testing. An annual verification would be a good place to start and would have saved me a heart attack two months ago.

I though I read that Mike Holt is involved in updates and recommendations to NEC updates. I'm hoping this request saves one life. The life it saves just might be yours.

 

[don_resqcapt19]

An open svc neutral to my home, unknown for 7-10 years, resulted in turning my plumbing into a sacrificial anode for the power company and thinning copper plumbing under the foundation that created pinholes in 15 year old copper pipes.

Most studies on this issue say that AC does not cause that type of damage to piping. In most case that type of damage is caused by the water chemistry.

...
I though I read that Mike Holt is involved in updates and recommendations to NEC updates. I'm hoping this request saves one life. The life it saves just might be yours.

Anyone can submit a public input for a change to the NEC. The public inputs for the 2020 NEC must be submitted by 5pm eastern time on November 3, 2017 if you use the online submission system.

Like I said before, I am not aware of a device on the market that will detect an open service neutral. With a common underground water piping system being used as a grounding electrode and bonded to the electrical system at every service, it would be hard to detect an open service neutral as you would not see the normal symptoms of an open neutral.

 

[fant]

Thinning pipes topic

Thinning pipes topic

Most studies on this issue say that AC does not cause that type of damage to piping. In most case that type of damage is caused by the water chemistry.
Anyone can submit a public input for a change to the NEC. The public inputs for the 2020 NEC must be submitted by 5pm eastern time on November 3, 2017 if you use the online submission system.

Like I said before, I am not aware of a device on the market that will detect an open service neutral. With a common underground water piping system being used as a grounding electrode and bonded to the electrical system at every service, it would be hard to detect an open service neutral as you would not see the normal symptoms of an open neutral.

Thanks for your input, Don.
My background is process troubleshooting. I'm constantly looking for opportunities to gather data and solve mysteries. During the discovery process - while plumbers were tunneling under my home and evaluating/replacing damaged copper pipes, I had the opportunity to compare two (almost) identical sub-slab copper pipe supply systems from main shut-off (both meter and front of the house) through the slab penetrations. The only difference between these two systems being one hot water tank was tied to the earth ground (home run to svc mains - home breaker panel 15 feet away) and the hot water tank next to it was not. They are tied to the same (common) input line, so they would electrically be in parallel and satisfying NEC. The house is divided into two zones for the hot water distribution and both tanks also feed second story bathrooms.

Only the piping attached to the grounded water tank suffered any changes. The second (other) half of the distribution copper pipes showed no wear or thinning. The pipe thinning (oxidation) is on the exterior of the copper pipes. I collected all the replaced copper pipe and stored it in my garage for future evaluation - I still have the damaged pipes. I also have pictures of the pipes (and leaks in action) before anything was replaced. The fact that one branch was damaged and one branch was not is what set me off on this path of discovery. This process also required 7-10 years to create a 2mm diameter hole at a bend, but there was not just one leaking location.

I have yet to find any research showing the prolonged affects of current on exposed copper that is in contact with the earth, but I'm still looking. All I know is what I have observed and recorded on my property. Insurance company does not care and electric company does not care, but I've lost $100,000+ in (uncovered) property damages and repairs, and close to the same in (uncovered) medical bills.

 

[al hildenbrand]

I have yet to find any research showing the prolonged affects of current on exposed copper that is in contact with the earth, but I'm still looking.

Maybe you wrote it, but I didn't understand. Is your water supply from a well, or from a municipal water utility? And, if supplied by a municipal water utility, are there other neighbors that are supplied from the same electric utility power transformer that supplies your home?

 

[fant]

reply

reply

Maybe you wrote it, but I didn't understand. Is your water supply from a well, or from a municipal water utility? And, if supplied by a municipal water utility, are there other neighbors that are supplied from the same electric utility power transformer that supplies your home?

Al - municipal water supply for homes, was QEST 3/4" from meter at street to shut off at front of house. Copper from shut off under slab to each of the penetrations through the slab, then copper throughout the house above the slab. The water supply was electrically isolated from the municipal water supply (QEST plastic was replaced after discovery, per code), but there is a direct electrical connection to the neighborhood through metal natural gas lines.

As mentioned before, I feel safe in saying that momentary discharge of current through the copper or metal plumbing (to earth) is the intention of NEC and its recommendations, but since there is presently no recommendation (periodic maintenance procedure) to verify that the svc neutral circuits are healthy and functioning, the power companies will verify that the current running from the transformer to the meter is being monitored and charged to the customer, but the return current path from the meter (svc neutral) is never checked until a customer complains. By the time a customer complains there is a dangerous situation for the customer and public with both charged plumbing and electrically hot natural gas piping.

 

[iwire]

I think you may not understand just how common open neutrals are and how rarely they cause injuries or property damage.

You are looking for a major change for an event that rarely causes serious issues.

 

[fant]

transformer supply answer

transformer supply answer

System here is for multiple homes to be supplied with home run lines from a transformer. Each home has its own dedicated set of 3 cables (L1, L2, N) that are run underground from the transformer to the foundation and meter on the home.

 

[ActionDave]

System here is for multiple homes to be supplied with home run lines from a transformer. Each home has its own dedicated set of 3 cables (L1, L2, N) that are run underground from the transformer to the foundation and meter on the home.

It is the same as nearly every home located inside city limits and subdivision in the United States.

Well, lots of them are fed overhead, still multiple houses fed from a common transformer is the norm.

 

[ron]

I agree, no NEC required sensing of an open neutral.

Generally if there is an open neutral condition, there are symptoms shown at the home that would lead to indirect detection.

The power path from piping back to the source grounded conductor (if the normal neutral path to the source grounded conductor is no good) is through the earth which is not a good conductor, so for a 120/240V 1ph system, there would be L-N voltage issues that would show as dim / bright incandescent lighting and equipment damage due to high/low L-N voltage issues.

 

[don_resqcapt19]

Al - municipal water supply for homes, was QEST 3/4" from meter at street to shut off at front of house. Copper from shut off under slab to each of the penetrations through the slab, then copper throughout the house above the slab. The water supply was electrically isolated from the municipal water supply (QEST plastic was replaced after discovery, per code)

What code required the replacement of the water pipe?

but there is a direct electrical connection to the neighborhood through metal natural gas lines.

Not very likely...as far as I know all of the gas utilities used a dielectric fitting to provide electrical isolation between the building gas piping and their underground gas piping system.

 

[al hildenbrand]

The water supply was electrically isolated from the municipal water supply (QEST plastic was replaced after discovery, per code), but there is a direct electrical connection to the neighborhood through metal natural gas lines.

Thank you for answering my first question.

Because your response includes the comment about the metal natural gas (utility ???) lines, I re-ask about your electric supply, with slight rewording, how many neighbors are supplied from the same electric utility transformer that your home's electrical service is connected to.

And, as a second question, I ask if you have investigated the physical characteristics of the natural gas piping and routing? FYI, in my limited experience and knowledge, di-electric union(s) are used at the customer gas meter connection to the supply piping, the effect of which is to electrically isolate the underground pipe from the premises gas piping system. Maybe your local utility has a different policy?

The thrust of my questions is towards an approximate circuit diagram, including probable resistances, of the multiple parallel current paths back to the source (the electric utility transformer grounded service conductor terminal) and the Main Bonding Jumper (as defined in Article 100 of the National Electric Code - NEC).

And, as a third question: What year was the permit issued for the construction of your home? This will fine tune some of our answers, by knowing the version of the NEC likely in effect during construction.

 

[user 100]

What code required the replacement of the water pipe?

Not very likely...as far as I know all of the gas utilities used a dielectric fitting to provide electrical isolation between the building gas piping and their underground gas piping system.

And, as a second question, I ask if you have investigated the physical characteristics of the natural gas piping and routing? FYI, in my limited experience and knowledge, di-electric union(s) are used at the customer gas meter connection to the supply piping, the effect of which is to electrically isolate the underground pipe from the premises gas piping system. Maybe your local utility has a different policy?

Could be some sort of weird local thing about the water pipe needing replaced(?)

About the gas pipe- It could be that there were a couple of failed dielectric fittings in some of the meters or someone did a huge no-no and jumpered around the meter- gas co.s will nail your butt big time for that one.:happyyes:

 

[JFletcher]

Most studies on this issue say that AC does not cause that type of damage to piping. In most case that type of damage is caused by the water chemistry.
Anyone can submit a public input for a change to the NEC. The public inputs for the 2020 NEC must be submitted by 5pm eastern time on November 3, 2017 if you use the online submission system.

Like I said before, I am not aware of a device on the market that will detect an open service neutral. With a common underground water piping system being used as a grounding electrode and bonded to the electrical system at every service, it would be hard to detect an open service neutral as you would not see the normal symptoms of an open neutral.

Neither am I, but wouldnt a simple jumper from panel to xfmr (thus creating a loop) with circuitry to monitor and detect an open circuit work? If it detects open, either the jumper or the neutral has failed. If one wanted to get fancy, Im sure one could also include an ohmmeter, and RF transmitter to a NC contactor on the mains that would instantly open upon signaled loss of svc neutral continuity, thus preventing damage to 120V and single phase equipment. I believe such a device could also be made to not normally carry current. or more simple, a second identically sized service neutral.

 

[iwire]

, but wouldnt a simple jumper from panel to xfmr (thus creating a loop) with circuitry to monitor and detect an open circuit work? If it detects open, either the jumper or the neutral has failed.

No, that would not work due to the multiple bonds to ground.