Open Service Neutral GFCI/RCD Detector

[mbrooke]

I see.

Say. How many percentage of Americans know the meaning of the utility transformer centertap and it's relationship to grounding of appliances chassis? In the Philippines, 99.9999% (or almost all) of house owners don't know the meaning utility transformer centertap and why the Equipment Grounding Conductor (EGC) must be connected to it to trip breakers when hot shorts to ground in the metal chassis. In fact. I didn't even know this when I spent 5 years in college studying Electronics Engineering (with some electrical subjects). It was only after an American Electrical Engineer who worked in nuclear power plants taught me about how to recognize my country transmission system and general concept of isolation transformers 3 months ago which I need to use to drive 120v surge protector to protect a sensitive fire alarm system with universal power supply (88v to 265v) with 300v surge ceiling that I learnt the principle of the utility transformer centertap to grounding of appliance/equipment metal chassis. In the USA, do 50% or more of home owners know the meaning of it? or only 5%. what do you think?

Difficult to gauge the number. There are many who mistakenly assume the ground clears a fault which is incorrect. But here is the thing: Most Americans turn to the internet or Home Depot wiring books. They explain the function of an EGC and how it works and where the power goes back to the center tap. Yes not all the internet sites are correct, but there is much greater chance they will get the correct information somehow.

 

[mbrooke]

We have too many electricians that don't fully understand grounded, grounding, neutral, center tap....no point in trying to answer how many Americans in general understand such things.

I think a major part comes from terms being incorrect. An equipment grounding conductor has little to do with the earth.

 

[mbrooke]

Leave them floating or ungrounded. Now what problem do you have?

Same issue- if not worse. Its only a matter of time before a phase becomes faulted making the system a grounded one.


FWIW Norway used to be IT and still is in existing installations. The homes all had EGC, a grounding system and earth electrodes. Worked well- up until homes always had standing ground faults. If the earth resistance was low enough or there was some type of metallic interconnection between homes there would be a war with blowing fuses between residences. If not structures would remain energized at 230 volt potential (building 1 had A phase grounded building 2 B phase grounded). This has resulted in many fires over the years, many times greater then the rest of Europe using TN earthing. The ideal solution to this problem would have been interconnecting all grounding systems between homes. Today the issue is mitigated with RCDs- if A phase grounds in one home and B phase in another, the current trickle between the two should trip an RCD.

 

[ptonsparky]

Same issue- if not worse. Its only a matter of time before a phase becomes faulted making the system a grounded one.
....

Exactly.

He has a center tap grounded system. Saying that No grounded conductor is taken to, or used, at homes because they do not have 120v loads does not change that fact.

 

[mbrooke]

Exactly.

He has a center tap grounded system. Saying that No grounded conductor is taken to, or used, at homes because they do not have 120v loads does not change that fact.

Yup. Code still requires that there be a neutral at the service, at minimum sized to the bonding jumper when no no neutral loads are present.


Honestly, I would speak with the POCO and see if a neutral can be dropped. I am curious what they say.

 

[tersh]

Same issue- if not worse. Its only a matter of time before a phase becomes faulted making the system a grounded one.


FWIW Norway used to be IT and still is in existing installations. The homes all had EGC, a grounding system and earth electrodes. Worked well- up until homes always had standing ground faults. If the earth resistance was low enough or there was some type of metallic interconnection between homes there would be a war with blowing fuses between residences. If not structures would remain energized at 230 volt potential (building 1 had A phase grounded building 2 B phase grounded). This has resulted in many fires over the years, many times greater then the rest of Europe using TN earthing. The ideal solution to this problem would have been interconnecting all grounding systems between homes. Today the issue is mitigated with RCDs- if A phase grounds in one home and B phase in another, the current trickle between the two should trip an RCD.

Does this scenerio also happen in the US where grounds can interact between buildings? In the Phils. We never seemed to have this occuring. Our soil are heavily connected to the transformer center via pole ground rods always installed such that one of the lines measured with respect to soil produced 120v. How can the interacting grounds between homes like in Norway happen? Pls give an example.

 

[mbrooke]

Does this scenerio also happen in the US where grounds can interact between buildings?

Not when there is a neutral going back to the transformer.

In the Phils. We never seemed to have this occuring. Our soil are heavily connected to the transformer center via pole ground rods always installed such that one of the lines measured with respect to soil produced 120v. How can the interacting grounds between homes like in Norway happen? Pls give an example.

Basically one phase becomes grounded in one home- the system is now corner grounded instead of ungrounded. Then another phase becomes grounded in another home. Full 230 volt potential exists between both structures. The current flow dries wood out as well the soil around the home. The dried wood over time can catch fire. Also anything interconnecting the two buildings like phone lines can also catch fire if they can not handle the current flow.


Here is a graphic showing pyrophoric carbonization. It mentions an open neutral, however anything that causes energized metal will cause it including opposite phases grounded in different structures without bonding between the grounding systems.

https://www.fireengineering.com/art...al-hazards-warrant-firefighter-vigilance.html

"But how did electricity get into the lath?" we asked. "There are no wires or water pipes anywhere near the point of origin." The troubleshooter explained that, in his experience, the fire was probably a result of a combination of problems with the building`s electrical wiring. First, he had to rule out that the power company`s neutral leg of the electric service wasn`t "open" (inadequate or had no capacity to conduct electricity). If his company`s neutral was open, current could not return normally to the transformer and would tend to "search" for another path to reach ground. Also, this old building still had most of its original wiring, consisting mainly of metal-clad BX cable. Like metal conduit, BX achieves its path to ground through its metal covering. A loose connection or a separation anywhere along the spiral metal sheath can break the continuity. If the BX happened to be in contact with anything metallic--say the plumbing or metal lath--either could become the new path to ground.


Another factor was the age of the building. The years can take a toll on wiring, giving it plenty of opportunity to "leak" electricity--insufficient current to trip a circuit breaker but enough to cause shocks and, over time, fires. Wiring can develop worn spots in its insulation, particularly where it is crammed into tight spaces, is jammed around sharp corners, and penetrates floors. A nail or screw that inadvertently penetrates wiring inside of a wall can energize any metallic object it touches.



The troubleshooter further explained that all piping systems, ventilation ductwork, metal structural members, and even aluminum siding can become energized. He told of a situation in which a restaurant`s gas piping became energized. The pipe was not connected to any electrical appliances and was not bonded to the electrical system. Evidently, a rat chewed through the insulation of a nonmetallic sheath cable, exposing the wires, which energized the gas piping. The tendency of current to use metallic objects to reach ground is increased significantly if the normal path to ground is interrupted by a section of plastic pipe, which cannot conduct electricity.



A voltmeter confirmed the power company troubleshooter`s suspicion: When the power was restored, wire lath nailed to the burnt stud was energized with 10 volts. The current flowing through the lath was sufficient to cause the lath to act like a heating element. The result was a slow, gradual process of heating the wood. It could have taken months or even years for this low-grade heat source to decompose the cellulose in the wood to a point that it would undergo the phenomenon of pyrophoric carbonization, which would gradually lower the ignition temperature of the wood and eventually ignite the stud.

In Norway most homes are wood, so when it happened fire was a given. In the Philipines I am not sure how homes are built, but it concrete the risk is much smaller should something become electrified.

 

[kwired]

But if your electricians and engineers understood the grounded system you have, you wouldn’t be attempting to make your own first aid kit.

You are not required to ground that center tap to make those used transformers give you 240 volts. Leave them floating or ungrounded. Now what problem do you have?

Exactly. They can even ground one end and leave center tap floating and have what Europeans typically have.

I think a major part comes from terms being incorrect. An equipment grounding conductor has little to do with the earth.

I have concluded we can change term names and there will still be confusion, people need to learn what the terms mean regardless of what name they are given.

Does this scenerio also happen in the US where grounds can interact between buildings? In the Phils. We never seemed to have this occuring. Our soil are heavily connected to the transformer center via pole ground rods always installed such that one of the lines measured with respect to soil produced 120v. How can the interacting grounds between homes like in Norway happen? Pls give an example.

Is there a primary conductor that is grounded many times and bonded to the secondaries? That creates a pretty reliable earth reference over a large area. Lose one electrode here or there and it often has little impact on overall system performance.

 

[tersh]

Not when there is a neutral going back to the transformer.








Basically one phase becomes grounded in one home- the system is now corner grounded instead of ungrounded. Then another phase becomes grounded in another home. Full 230 volt potential exists between both structures. The current flow dries wood out as well the soil around the home. The dried wood over time can catch fire. Also anything interconnecting the two buildings like phone lines can also catch fire if they can not handle the current flow.


Here is a graphic showing pyrophoric carbonization. It mentions an open neutral, however anything that causes energized metal will cause it including opposite phases grounded in different structures without bonding between the grounding systems.

https://www.fireengineering.com/art...al-hazards-warrant-firefighter-vigilance.html







In Norway most homes are wood, so when it happened fire was a given. In the Philipines I am not sure how homes are built, but it concrete the risk is much smaller should something become electrified.

In poor areas. Home are made of wood. If one home got burnt. It spreads to several hundreds of homes.

What do you mean if there is neutral getting back to transformer? You mean if the pole is grounded? Yes floating transformers may cause that scenerio like in Norway. Thats the first thing i thought of when i pondered what if ungrounded isolation transformer were used to drive homes. I realized what if soil is not connected consistently to one phase.

In Phils. Utility poles always provide 3 wire.. but contractors put 2 wire only bec all appliances have no EGC. In fact i need to connect grounding just to protect the Siemens sub metal chasis. Without it. I wouldnt have any motive to initiate grounding.

 

[kwired]

In poor areas. Home are made of wood. If one home got burnt. It spreads to several hundreds of homes.

What do you mean if there is neutral getting back to transformer? You mean if the pole is grounded? Yes floating transformers may cause that scenerio like in Norway. Thats the first thing i thought of when i pondered what if ungrounded isolation transformer were used to drive homes. I realized what if soil is not connected consistently to one phase.

In Phils. Utility poles always provide 3 wire.. but contractors put 2 wire only bec all appliances have no EGC. In fact i need to connect grounding just to protect the Siemens sub metal chasis. Without it. I wouldnt have any motive to initiate grounding.

You don't have exposed metal components (frames of appliances, fixtures, wiring methods, etc.) other than the breaker panel enclosure that could become energized if something happened to contained conductor insulation?

 

[mbrooke]

In poor areas. Home are made of wood. If one home got burnt. It spreads to several hundreds of homes.

What do you mean if there is neutral getting back to transformer?

If you have a fault in say the panel enclosure, it will trip a breaker. The frame and grounding system its connected to will not sit energized.

You mean if the pole is grounded? Yes floating transformers may cause that scenerio like in Norway. Thats the first thing i thought of when i pondered what if ungrounded isolation transformer were used to drive homes. I realized what if soil is not connected consistently to one phase.

If each home had an un-grounded transformer right at the service you could have any phase fault in any home and it would not effect other structures in that no current would pass between them. However, if you had different phases fault in the same home, anything current path between them might cause a problem.

In Phils. Utility poles always provide 3 wire.. but contractors put 2 wire only bec all appliances have no EGC. In fact i need to connect grounding just to protect the Siemens sub metal chasis. Without it. I wouldnt have any motive to initiate grounding.

Yup- wish it wasn't the case however.

 

[mbrooke]

I have concluded we can change term names and there will still be confusion, people need to learn what the terms mean regardless of what name they are given.

I disagree. You call things by their name, not obfuscate. You become addled being subjected to stroop.

 

[kwired]

I disagree. You call things by their name, not obfuscate. You become addled being subjected to stroop.

And we use names that have similar meanings and it only adds confusion - that is why the need for Art 100 - this is the definition as it applies when using a specific word anywhere in the document.

If we changed every occurrence of "ground" whether a stand alone word or part of another word or phrase to "earth" or to any other word - we would still have about same level of misunderstanding we have now. If we made up a new word to replace it with that currently is not defined in any dictionary, it would still be about same level of misunderstanding IMO. I will add it will be even more confusing to those that refuse to even look at the art 100 definitions though.

 

[Adamjamma]

Yup. Code still requires that there be a neutral at the service, at minimum sized to the bonding jumper when no no neutral loads are present.


Honestly, I would speak with the POCO and see if a neutral can be dropped. I am curious what they say.

I agree, this might be the least costly way of fixing Tersh's problems... get a neutral dropped, ground the panel, run grounds and neutrals within his parents home... all the extra concerning the RCD before the GFCI is then not needed..in fact, simply running the neutral to the residence and getting it in the panel means so much more safety that the cost of that one wire should be minimal... each gfci breaker may cost as much and protects so much less...
at least from what little I know of the subject

 

[kwired]

I agree, this might be the least costly way of fixing Tersh's problems... get a neutral dropped, ground the panel, run grounds and neutrals within his parents home... all the extra concerning the RCD before the GFCI is then not needed..in fact, simply running the neutral to the residence and getting it in the panel means so much more safety that the cost of that one wire should be minimal... each gfci breaker may cost as much and protects so much less...
at least from what little I know of the subject

Cost less to just leave center tap float and ground one of the two conductors that are being used. 240 volt two wire grounded system, install main bonding jumper at the service equipment. You need additional grounding conductors run beyond the service either way.

 

[mbrooke]

And we use names that have similar meanings and it only adds confusion - that is why the need for Art 100 - this is the definition as it applies when using a specific word anywhere in the document.

If we changed every occurrence of "ground" whether a stand alone word or part of another word or phrase to "earth" or to any other word - we would still have about same level of misunderstanding we have now. If we made up a new word to replace it with that currently is not defined in any dictionary, it would still be about same level of misunderstanding IMO. I will add it will be even more confusing to those that refuse to even look at the art 100 definitions though.

Canada calls it a bonding conductor. UK circuit protective conductor. Much more well defined.

 

[mbrooke]

I agree, this might be the least costly way of fixing Tersh's problems... get a neutral dropped, ground the panel, run grounds and neutrals within his parents home... all the extra concerning the RCD before the GFCI is then not needed..in fact, simply running the neutral to the residence and getting it in the panel means so much more safety that the cost of that one wire should be minimal... each gfci breaker may cost as much and protects so much less...
at least from what little I know of the subject

I agree. Even if his circuits are two wire, having the panel with a noodle will make things easier in the future.

 

[mbrooke]

Cost less to just leave center tap float and ground one of the two conductors that are being used. 240 volt two wire grounded system, install main bonding jumper at the service equipment. You need additional grounding conductors run beyond the service either way.

This is how 90% of the world does it. Including us at bill boards and traffic lights. Classic TN-C-S.

 

[tersh]

I agree, this might be the least costly way of fixing Tersh's problems... get a neutral dropped, ground the panel, run grounds and neutrals within his parents home... all the extra concerning the RCD before the GFCI is then not needed..in fact, simply running the neutral to the residence and getting it in the panel means so much more safety that the cost of that one wire should be minimal... each gfci breaker may cost as much and protects so much less...
at least from what little I know of the subject

This is the situation why we can't add a third grounding wire to service entrance:

My parent house is part of a 5 house compound (called townhouses). The utility service entrance is outside the red gate. There are 2 houses between the utility and my parent house which is at the back. Our feeder is under the driveway. We need to demolish the driveway just to access the feeder and wires. Distance to front is 35 meters.

This is our service entrance panels outside the compound in the street:​

You can see the feeder is small. And it is about 35-40 meters to the house main panel crossing many bends under the driveway. If we pull it out. We can no longer put a new 3 wire inside because the feeder is corroded and rusty (they put the wires at every angle during construction before driveway was concreted).

So how do you propose we replace 40 meters of new wires under the driveway (or even adding just the ground wire)? The neighbors won't allow. They don't want any power interruption or not able to use the driveway during the repair or destroying it (the new concrete won't blend with old one). They don't use any ground wire just like millions and since nothing happens to them. They thought it was superfluous. And lastly, they don't want my parent 40 meters wires and new feeder to hang on their driveway.
​

So the only sound solution is 100A RCD (30mA) just to protect the Siemens subpanel. All the appliances in the homes will be protected by GFCIs. Hence pls. give me the most advanced RCD model in the planet, perhaps one you can even monitor with smartphone

 

[Adamjamma]

well.. wonder about the solution some have here of grounding one of the two live wires... not sure if it works or not but... if it worked and created a UK style 240 volt system..well...
I dont have the guts or the knowledge to try it, however.