List of all nuasance leakage tripping current sourcces of GFCI

[tersh]

Do you have a copy of the Philippines code to hand? No, neither do I, other than the link I posted.

The two breakers in the OP’s third photograph look like VO-ELCB’s, they’ve not been installed in the UK since the late 60’s early 70’s although they keep cropping up now and again.

We copy the US NEC every decade and just changed the units from inches to mm. This is so because the US designed our country electricity using the same 120/240v split phase at the US. However, after the US left, the government decided to use only the 240v phase and phase and omit 120v, the reason was so our countrymen can buy locally manufactured products like 240v lamps and avoid buying from the US. However when neutral disappears so is the grounding, that is why manufacturers like refrigerators or washing machine don't have any 3 prong plug, only 2 prong because the grounding is not used. So the neutral in the centertap is only connected to pole ground rod to ground the secondary and no other use (except for large commercial establishments or factory).

And remember even city halls don't follow the electrical codes.. because we just copy them from the US for formality. What are strictly followed are only wire sizes, ampere and breaker sizes. Now let's talk about my RCBO (and not discuss the code).

What is an "

VO-ELCB"? The following is zoomed in picture of my main breaker.​

It's 240v phase to phase 2-pole made in US.. the same you used in US for the black and red wire. And note there was no neutral bar in my main panel because we don't use the neutral.

For the 16 breakers. I know if leakage of each is 4mA. It won't trip the individual 5mA 2-pole 240v GFCI. So 4x16 = 65mA. Therefore is 100mA residual current tripping current in main breaker (the 2nd disconnect) enough.

Also important. How large is the leakage current from capacitive coupling of wiring in houses usually?

 

[Adamjamma]

Do you have a copy of the Philippines code to hand? No, neither do I, other than the link I posted.

The two breakers in the OP’s third photograph look like VO-ELCB’s, they’ve not been installed in the UK since the late 60’s early 70’s although they keep cropping up now and again.

No, I do not have the Philippines code except the one you just posted..lol.. and the only copy so far of the Jamaican code I have seen was in a library there... the copier was broke or would have copied it..lol... hard to find any copies of it... kinda like the Jamaican road map...

 

[tersh]

No, I do not have the Philippines code except the one you just posted..lol.. and the only copy so far of the Jamaican code I have seen was in a library there... the copier was broke or would have copied it..lol... hard to find any copies of it... kinda like the Jamaican road map...

In my country the utility and government don't follow the codes. I'm not making it up. For example in the following forum you can read experiences of different walks of life about no grounding. Here's a quote:

https://www.philippines-expats.com/topic/29039-grounding-of-electric-appliances/

"With our new rental we just bought several appliances. I noticed that both the refrigerator and microwave came with a separate ground wire. The instructions said to connect it for safety purposes but not where to connect it to.​

Now our house has both 2 pronged and 3 pronged outlets, but I know in the Philippines just because something is 3 pronged does not mean it is properly grounded.

I know nothing to speak of about electricity but don't believe there is any kind of grounding rod in the kitchen. Is there any value to using these grounding wires and where do I connect them to? "

someone replied in page 2:

"The OP asked what he should do with the ground wire from his Refrigerator. I mentioned that he should ground it to a water pipe, this is a safe and usual practice, not dangerous. One end of the wire is already grounded to the fridge, the free end to a grounding rod or water pipe as i was taught"

Normal homes don't have 3-wire to access the neutral in the centertap. Contractors omitted putting the third wire because appliances don't have 3 prong plugs, only 2 prong so no use to add 3-wire. And city hall never checked the third wire. This is even when it's in the plan. All of them ignored the third wire even if it's the code we copied from NEC. All homes of people
I know have 2 wire only. The grounding is just to connect to metal pipes.

Later in page 4:

"Just this Tuesday we were told one of the wifes old friends died from an electric shock from a rice cooker !"

So forget looking at the Philippine codes. Since I can't access the neutral in the centertap. And I can't rely on just local grounding electrode. Then I will use GFCI and RCBO in the entire house. No less than Mike Holt himself predicted that in 2020 all outlets will use GFCI!

So help me find the best model and brand that offers 125A breaker with 100mA residual tripping current. I guess this is enough to avoid nuisance tripping? Remember it will just protect the main panel metal enclosure touching to live. All the rest of appliances with be protected by 16 pcs of 5mA GFCI breakers. What is the largest mA that capacitive coupling of wiring in the house that let some leakage current escape? Thanks.

​

 

[Adamjamma]

problem is that unless you specifically buy the 2 space gfci breakers, it will not work, and even then am not too sure... because the regular gfci breaker is designed for 120 wires, which you have, but with a neutral, which you are not using... so you need to run the 240 style if gfci... which in USA is double breaker or tied handle breaker. Neutral would need a grounded source for it to work since you have no neutral running in actuality.

Other choice is RCD like in Europe but... it specifically is designed for a neutral close to zero potential and will trip if the neutral is running close to 120 volts such as like the USA. I have checked with several of the manufacturers here in the UK who all say not to use their system on US style of 240 due to the neutral carrying too much voltage. I am not an expert however so surely someone here has more knowledge to give you.

The reason for suggesting the rebar in concrete is a concrete encased electrode is one way of getting some ground, but this is usually done using a rebar that is part of the foundation... not sure what technique your foundation uses there.

Unfortunately, I can see no easy way for you to fix your parents home unless you find someone who can drill a deep enough hole or two for you to put the ground rods into. even then trying to make a bad situation safe is one I do not envy you for trying to do. Hopefully, some one here can point you in a better direction.

 

[tersh]

problem is that unless you specifically buy the 2 space gfci breakers, it will not work, and even then am not too sure... because the regular gfci breaker is designed for 120 wires, which you have, but with a neutral, which you are not using... so you need to run the 240 style if gfci... which in USA is double breaker or tied handle breaker. Neutral would need a grounded source for it to work since you have no neutral running in actuality.

No problem. Even without any neutral connected to the centertap of the utility transformer. My US based Siemens QF230A/QF260A works perfectly. A former tech at Siemens taught me how to use a small 50w autotransformer to power the GFCI white pigtail and it works perfectly (the only purpose of the 120v is to power the internal circuitry of the GFCI).

I have no problem with 16 pcs of it protecting most of the the appliances. Although I may have to use RCD for refrigerators because these trip on 5mA GFCI. Some said it trip during defrosting when the inductor is working.. true? What mA must I get so refrigerators won't trip?

Other choice is RCD like in Europe but... it specifically is designed for a neutral close to zero potential and will trip if the neutral is running close to 120 volts such as like the USA. I have checked with several of the manufacturers here in the UK who all say not to use their system on US style of 240 due to the neutral carrying too much voltage. I am not an expert however so surely someone here has more knowledge to give you.

You mean RCD in Europe has polarity? Any reference I could read? I need RCBO with 100mA tripping where it can take the full US 240v black and red wire.

The reason for suggesting the rebar in concrete is a concrete encased electrode is one way of getting some ground, but this is usually done using a rebar that is part of the foundation... not sure what technique your foundation uses there.

Unfortunately, I can see no easy way for you to fix your parents home unless you find someone who can drill a deep enough hole or two for you to put the ground rods into. even then trying to make a bad situation safe is one I do not envy you for trying to do. Hopefully, some one here can point you in a better direction.

 

[kwired]

Is the 240 volt supply grounded?

What does single pole breakers you have in the panel supply?

You probably could ground one of your conductors if the supply isn't grounded, but those breakers you have shown likely are 120/240 rated breakers and weren't designed to operate at 240 volts to ground.

Why not put in a transformer to derive a neutral if you want 120/240 and ground the secondary neutral? Seems like a better idea to me than trying to use ground fault protection on entire system.

 

[tersh]

Is the 240 volt supply grounded?

No. It's just like in the US where only the centertap is grounded at the utility pole but in the Philippines, 120v not supplied inside the home.

What does single pole breakers you have in the panel supply?

There are all 2 poles. All 240v.

You probably could ground one of your conductors if the supply isn't grounded, but those breakers you have shown likely are 120/240 rated breakers and weren't designed to operate at 240 volts to ground.

No. If I ground one of the red or black conductor, it can cause short circuit because the utility transformer is grounded at the centertap neutral, just like in the USA. All those breakers are 240v. We never use 120v because of the complication of teaching millions how to do proper bonding and dangerous of open neutral service.

Why not put in a transformer to derive a neutral if you want 120/240 and ground the secondary neutral? Seems like a better idea to me than trying to use ground fault protection on entire system.

No. The power system is just like in USA. Imagine only the 240v are used and neutral only used for grounding. But in the Philippines, grounding is not used because all appliances don't use 3 prong plug with grounding.

Therefore using all GFCI and RBCO is the only good option left.

 

[kwired]

No. It's just like in the US where only the centertap is grounded at the utility pole but in the Philippines, 120v not supplied inside the home.



There are all 2 poles. All 240v.



No. If I ground one of the red or black conductor, it can cause short circuit because the utility transformer is grounded at the centertap neutral, just like in the USA. All those breakers are 240v. We never use 120v because of the complication of teaching millions how to do proper bonding and dangerous of open neutral service.



No. The power system is just like in USA. Imagine only the 240v are used and neutral only used for grounding. But in the Philippines, grounding is not used because all appliances don't use 3 prong plug with grounding.

Therefore using all GFCI and RBCO is the only good option left.

You can't use an autotransformer because you would be attempting to ground two points in the same system, you can use isolation transformer and create a separately derived system and ground that separately derived system at any point you wanted and it won't care what is or isn't grounded on the supply side. This still leaves you with some risk should there be a ground fault on primary side.

Your appliances with only two wire cords likely are "double insulated" and would essentially still be the same thing even if you had an equipment grounding conductor at the receptacle.

 

[tersh]

You can't use an autotransformer because you would be attempting to ground two points in the same system, you can use isolation transformer and create a separately derived system and ground that separately derived system at any point you wanted and it won't care what is or isn't grounded on the supply side. This still leaves you with some risk should there be a ground fault on primary side.

No. I'd only use 50w autotransformer just to power the Siemens SF230A 2-pole breaker internal circuitry. One can't use isolation transformer to power the Siemens. It needs neutral and can be provided by the autotransformer 110v output. This is the only purpose of the autotransformer and not for isolation and no other use in the panel.

Your appliances with only two wire cords likely are "double insulated" and would essentially still be the same thing even if you had an equipment grounding conductor at the receptacle.

Yes. The centertapped of the utility transformer is connected to the pole ground rod in the following:

So just imagine USA ac system but with the neutral only used as grounding and not for powering any 120v to avoid the problem of open service neutral. This can kill more citizens in third world country than ground fault.

The reason I can't tap to it is because we have to destroy the driveway to pull out old feeder and replace with new and neighbors won't allow that.

 

[kwired]

No. I'd only use 50w autotransformer just to power the Siemens SF230A 2-pole breaker internal circuitry. One can't use isolation transformer to power the Siemens. It needs neutral and can be provided by the autotransformer 110v output. This is the only purpose of the autotransformer and not for isolation and no other use in the panel.



Yes. The centertapped of the utility transformer is connected to the pole ground rod in the following:

So just imagine USA ac system but with the neutral only used as grounding and not for powering any 120v to avoid the problem of open service neutral. This can kill more citizens in third world country than ground fault.

The reason I can't tap to it is because we have to destroy the driveway to pull out old feeder and replace with new and neighbors won't allow that.

The isolation transformer I'm talking about would power everything, and provide a grounding reference, only thing it won't help with is if there would be a ground fault on transformer primary circuit.

Of course if you have no equipment grounding conductors run with branch circuits it still doesn't do that much for you.

I think you need to pick North American wiring standard or a European wiring standard and stick with it and not mix and match to have a safer system. Both still have a conductor that is "earthed" that typically bonds to non current carrying metal components for similar reasons in either system.

 

[tersh]

The isolation transformer I'm talking about would power everything, and provide a grounding reference, only thing it won't help with is if there would be a ground fault on transformer primary circuit.

Of course if you have no equipment grounding conductors run with branch circuits it still doesn't do that much for you.

I think you need to pick North American wiring standard or a European wiring standard and stick with it and not mix and match to have a safer system. Both still have a conductor that is "earthed" that typically bonds to non current carrying metal components for similar reasons in either system.

In the Philippines, we used North American wiring standard, only in the province do they use 240v to neutral. Here an american who immigrated to the Philippines tried to explain his experiences:

https://myphilippinelife.com/philippine-electrical-wiring/

Of course I won't use a 10,000W isolation transformer.

Do you know what is the best residual current tripping current so it won't trip spontaneiously.. is 100mA ok for whole house RCBO?

 

[kwired]

In the Philippines, we used North American wiring standard, only in the province do they use 240v to neutral. Here an american who immigrated to the Philippines tried to explain his experiences:

https://myphilippinelife.com/philippine-electrical-wiring/

Of course I won't use a 10,000W isolation transformer.

Do you know what is the best residual current tripping current so it won't trip spontaneiously.. is 100mA ok for whole house RCBO?

two wire 240 volts is not a North American standard and neither is RCD you are still mixing and matching two different standards no matter what you do.

Mixing and matching has resulted in you having a 240 volt 2 wire supply but with a third grounded point that hasn't been brought out for utilization, even if only utilization was going to be equipment grounding purposes. You have something that is constructed to two standards yet doesn't comply with either standard. Until you fully go with one standard or the other you will always have issues.

 

[winnie]

Wow, just wow.

The electrical system as described is the worst of all worlds in terms of shock hazard.

The electrical supply is _grounded_, but the grounded conductor is not brought to the service, so there is not a 'reliable fault current path'. This means that a short circuit between conductor and a chassis will not reliably open a circuit breaker.

Yet at the same time because the system is grounded, a person touching a circuit conductor and anything conductive to earth will likely get shocked.

Given this situation, I think that the install that tersh is contemplating having an electrician do is pretty reasonable.

However since he is going off from the local installation standards there is a significant chance of missing something important.

The point about power for the GFCIs is pretty key, and I think that using the autotransformer for power is a bit sketchy. I would want a written document from the manufacturer that this is acceptable, and would prefer to use GFCIs actually designed to work on 240V supplies.

If a refrigerator trips a GFCI on defrost (have you tested this), then I would consider the refrigerator broken, and replace it rather than use a higher trip threshold. Think about this: if you don't have an EGC, then any leakage current is going through the refrigerator chassis to something else surrounding the chassis, such as a person.

Regarding protecting the feeder: as long as the branch circuits are protected with class A GFCI devices, then protecting the feeder is only about protecting equipment. You don't need to detect the minimum possible leakage.

Be careful about fixating on only one portion of the system, and investing all of your resources to fix only one problem. GFCI devices are expensive, can be damaged by things like lightning surges, and provide some real protection from electric shock.

But in your pictures you show a standard breaker that looks like it is outside in a box that is rusted away. You might better spend money replacing that ordinary breaker with another ordinary breaker in a proper enclosure.

Find an electrician you trust who can look at the big picture, look at your budget, and best advise you what repairs you should priortize.

-Jon

 

[winnie]

In
Of course I won't use a 10,000W isolation transformer.

Do you know what is the best residual current tripping current so it won't trip spontaneiously.. is 100mA ok for whole house RCBO?

Why not? If you installed a large isolation transformer, then you would have a 'separately derived system'. You would have your own local neutral which you would then ground and bring to your panel. This would give you a completely standard 120/240V panel.

You have already stated that it is not practical to replace the existing 2 conductor circuits with 3 conductor (2 circuit conductors plus ground); but you have not really said why. Presumably the issue is cost; as has been said: anything can be built as long as the design is drawn on the back of a large enough check.

You want to spend money on a RCBO. You should very carefully ask if the money is better spent elsewhere.

-Jon

 

[tersh]

Wow, just wow.

The electrical system as described is the worst of all worlds in terms of shock hazard.

The electrical supply is _grounded_, but the grounded conductor is not brought to the service, so there is not a 'reliable fault current path'. This means that a short circuit between conductor and a chassis will not reliably open a circuit breaker.

Yet at the same time because the system is grounded, a person touching a circuit conductor and anything conductive to earth will likely get shocked.

I don't get this. If the system is grounded, why would a person touching a circuit conductor and anything conductive to earth will likely get shocked?? Were you describing the normal ground fault where hot line touches chasis? Or were you describing path of electricity from the pole utility ground rod passing through the soil and inside the house? But how could there be electricity in the pole ground rod when it is grounded??

Given this situation, I think that the install that tersh is contemplating having an electrician do is pretty reasonable.

However since he is going off from the local installation standards there is a significant chance of missing something important.

The point about power for the GFCIs is pretty key, and I think that using the autotransformer for power is a bit sketchy. I would want a written document from the manufacturer that this is acceptable, and would prefer to use GFCIs actually designed to work on 240V supplies.

If a refrigerator trips a GFCI on defrost (have you tested this), then I would consider the refrigerator broken, and replace it rather than use a higher trip threshold. Think about this: if you don't have an EGC, then any leakage current is going through the refrigerator chassis to something else surrounding the chassis, such as a person.

I read so much in the internet about warning not to use Refrigerators on GFCI because during defrosting when inductor runs, it radiates the current away so the GFCI trips. I thought it was normal operation.

Regarding protecting the feeder: as long as the branch circuits are protected with class A GFCI devices, then protecting the feeder is only about protecting equipment. You don't need to detect the minimum possible leakage.

Be careful about fixating on only one portion of the system, and investing all of your resources to fix only one problem. GFCI devices are expensive, can be damaged by things like lightning surges, and provide some real protection from electric shock.

But in your pictures you show a standard breaker that looks like it is outside in a box that is rusted away. You might better spend money replacing that ordinary breaker with another ordinary breaker in a proper enclosure.

Find an electrician you trust who can look at the big picture, look at your budget, and best advise you what repairs you should priortize.

-Jon

Remember I wanted to use an RCBO (Residual Current Circuit Breaker with Overcurrent) device replacing the main breaker in the second disconnect panel in order to protect the main panel itself like what if the bus bar melted the insulation and touches the main panel enclosure. I want the RCBO to trip when this happens instead of fire and sparks.

I can't connect to the service entrance neutral because the family lives in a house with 5 other houses inside. All the feeders run under the driveway (about 70 meters (230 feet) and neighbors won't allow jackhammering (concrete demolition) the driveway just to put the ground wire. They all don't use ground.

I'm not exaggerating when I say that 99% of houses in the Philippines don't have use grounding or EGC. Here is the American who migrated to Philippines who described it:
https://myphilippinelife.com/philippine-electrical-wiring/

"

Most Philippine houses are not wired with three-prong, grounded outlets. Most outlets have only a load wire and a neutral wire. The quality of grounding of the neutral wire can be uncertain due to improper earthing at the pole or in the residence. If you’ve spent any time in the Philippines, you’ve probably been repeatedly shocked by your computer, refrigerator and so forth. The metal parts of these appliances either have no ground (earth) connection and/or the neutral is not properly grounded. When you touch them with bare feet on a tile, you become the ground. Since bare feet on tile are a pleasure of Philippine retirement, this is best avoided."​

 

[JFletcher]

Regarding Autotransformers, see if they comply with 210.9, 450.4, and 450.5.

 

[winnie]

These are the sort of questions which are the reason that this is not a DIY discussion board. Given my understanding of the forum rules, this thread is only allowed to remain open because you have explicitly stated that you will be hiring an electrician to install the equipment which you decide you want.
With this in mind, I applaud your decision to educate yourself and will do my best to answer your questions, but you really don't fully understand how electricity works.

I don't get this. If the system is grounded, why would a person touching a circuit conductor and anything conductive to earth will likely get shocked?? Were you describing the normal ground fault where hot line touches chasis? Or were you describing path of electricity from the pole utility ground rod passing through the soil and inside the house? But how could there be electricity in the pole ground rod when it is grounded??

Electricity flows in a complete circuit, from the source, through the load(s) and back to the source. If you don't have a complete circuit then you don't get electric current flow.

Consider a bird sitting on a high voltage wire. There may be many amps flowing through the wire, and the wire might be at several thousand volts, but the bird is not part of a circuit and thus no current flows through the bird and it doesn't get a shock.

The same is found with electrical systems. If you have a true _ungrounded_ transformer secondary, then very little current flows through the _first_ connection to ground. There is always some current because of capacitive coupling which will complete the circuit, but in small ungrounded system you could touch one hot wire while standing in bare feet on wet sand and not get a shock.

By connecting the center tap of the transformer to a ground rod, a hazard is created by making the soil a possible circuit conductor. In general the benefits of such grounding outweigh the added risk, but part of this risk mitigation is bringing the neutral to the service entrance panel and requiring bonding of all 'non-current-carrying' metal (eg. water pipes, conduit, etc) to the same grounded neutral point.

If a hot wire touches a bonded chassis, then you get lots of current flow and this trips a circuit breaker.

The system that you describe has the downsides of grounding (creating a circuit path through the soil) with none of the safety details required in the US.

I read so much in the internet about warning not to use Refrigerators on GFCI because during defrosting when inductor runs, it radiates the current away so the GFCI trips. I thought it was normal operation.

Not correct. It is true that refrigerators are known to trip GFCIs, often because of the defrost heaters. However this is not because of any sort of radiation or inductive coupling; this is simply because of leaky insulation permitting a small amount of current to flow from the wires to the chassis. Proper electrical insulation will not leak much current, and a modern refrigerator should not trip a GFCI. The one in my kitchen is on a GFCI with no problems.

If the chassis had proper ground bonding, then this small leakage is not really a problem. But you don't have proper ground bonding, which means that this leakage is going to energize the frame or shock someone.

IMHO if you want the safety of GFCI protection rather than installing proper ground bonding (which I agree is probably crazy expensive and thus not practical) then put the fridge on the GFCI and if it trips, replace the fridge.

Remember I wanted to use an RCBO (Residual Current Circuit Breaker with Overcurrent) device replacing the main breaker in the second disconnect panel in order to protect the main panel itself like what if the bus bar melted the insulation and touches the main panel enclosure. I want the RCBO to trip when this happens instead of fire and sparks.

I can see the benefit of that approach, and agree that it would be better than what you have now. What I was trying to say was that you only have limited resources to make improvements. You should spend your money where you get the best improvement per dollar. Maybe the RCBO is the best approach (I don't know the costs), but maybe that money would be better spent on mechanical improvements to make it less likely that any part of the feeder would actually come in contact with the chassis.

Regarding the trip level of the RCBO: you do not select trip level based on nuisance tripping; you select it to protect whatever the RCBO is supposed to protect. You need to decide how much leakage current you can tolerate; if you need to make a system that will protect a person who touches it, then you need 6mA class A GFCI protection. If you want to protect from fire and sparks then the trip level can be quite a bit higher.

Good luck.

-Jon

 

[tersh]

These are the sort of questions which are the reason that this is not a DIY discussion board. Given my understanding of the forum rules, this thread is only allowed to remain open because you have explicitly stated that you will be hiring an electrician to install the equipment which you decide you want.
With this in mind, I applaud your decision to educate yourself and will do my best to answer your questions, but you really don't fully understand how electricity works.



Electricity flows in a complete circuit, from the source, through the load(s) and back to the source. If you don't have a complete circuit then you don't get electric current flow.

Consider a bird sitting on a high voltage wire. There may be many amps flowing through the wire, and the wire might be at several thousand volts, but the bird is not part of a circuit and thus no current flows through the bird and it doesn't get a shock.

The same is found with electrical systems. If you have a true _ungrounded_ transformer secondary, then very little current flows through the _first_ connection to ground. There is always some current because of capacitive coupling which will complete the circuit, but in small ungrounded system you could touch one hot wire while standing in bare feet on wet sand and not get a shock.

By connecting the center tap of the transformer to a ground rod, a hazard is created by making the soil a possible circuit conductor. In general the benefits of such grounding outweigh the added risk, but part of this risk mitigation is bringing the neutral to the service entrance panel and requiring bonding of all 'non-current-carrying' metal (eg. water pipes, conduit, etc) to the same grounded neutral point.

If a hot wire touches a bonded chassis, then you get lots of current flow and this trips a circuit breaker.

The system that you describe has the downsides of grounding (creating a circuit path through the soil) with none of the safety details required in the US.

Ah. I got your points. It's the standard danger of ground fault where if hot wire touches chassis and a person touches it with bare feet and there is not Equipment Grounded Conductor connected to the neutral and centertap of the transformer, the person can get shock or electrocuted unless the breaker can trip during initial ground fault. When you mentioned touching "circuit conductor". I thought you mean "circuit chassis". So I wonder why would anyone get shock by touching chasis and soil without any ground fault. If you meant circuit conductor as live wire.. of course everyone here knows touching live conductor with feet on ground can cause shock. Thanks for the info though. A floating utility transformer would be safer for the house but bad for the utility as lightning can damage the transformer or lightning may divert to the homes if no ground.

Don't worry. Expert electricians will install everything. I just need to find the right RCBO brand and model. Do you know what is the best brand? It should be 125A with 100mA tripping current. Can you estimate the mA of the capacitive coupling current of wiring in average houses?? I want to take it into consideration in computing the leakage current. Thanks.

About proper install of feeder in main panel. Of course it's proper. But the following main panel is already 25 years old. What if the insulation separating cooper bus bar and panel chassis short? The 16 GFCIs 2-pole breakers to be installed won't protect the panel chassis itself. Not even if the RCBO would be put in the main panel.

This is why the RCBO needs to be put in another panel (below) connected before the main panel. And the house just happened to have redundant one in the following. I can replace this with rail DIN type. But I want to make sure the 100mA won't suddenly trip even without any leakage. I know the rest of the 16 GFCIs can trip for their respective appliances. Do you know of any equipments that can't be protected by any RCDs because they always trip? Like airconditioning units? And do you know if anyone else installed RCBO in main panel breaker or only me?

Not correct. It is true that refrigerators are known to trip GFCIs, often because of the defrost heaters. However this is not because of any sort of radiation or inductive coupling; this is simply because of leaky insulation permitting a small amount of current to flow from the wires to the chassis. Proper electrical insulation will not leak much current, and a modern refrigerator should not trip a GFCI. The one in my kitchen is on a GFCI with no problems.

If the chassis had proper ground bonding, then this small leakage is not really a problem. But you don't have proper ground bonding, which means that this leakage is going to energize the frame or shock someone.

IMHO if you want the safety of GFCI protection rather than installing proper ground bonding (which I agree is probably crazy expensive and thus not practical) then put the fridge on the GFCI and if it trips, replace the fridge.



I can see the benefit of that approach, and agree that it would be better than what you have now. What I was trying to say was that you only have limited resources to make improvements. You should spend your money where you get the best improvement per dollar. Maybe the RCBO is the best approach (I don't know the costs), but maybe that money would be better spent on mechanical improvements to make it less likely that any part of the feeder would actually come in contact with the chassis.

Regarding the trip level of the RCBO: you do not select trip level based on nuisance tripping; you select it to protect whatever the RCBO is supposed to protect. You need to decide how much leakage current you can tolerate; if you need to make a system that will protect a person who touches it, then you need 6mA class A GFCI protection. If you want to protect from fire and sparks then the trip level can be quite a bit higher.

Good luck.

-Jon

 

[winnie]

Don't worry. Expert electricians will install everything. I just need to find the right RCBO brand and model. Do you know what is the best brand? It should be 125A with 100mA tripping current. Can you estimate the mA of the capacitive coupling current of wiring in average houses?? I want to take it into consideration in computing the leakage current. Thanks.

About proper install of feeder in main panel. Of course it's proper. But the following main panel is already 25 years old. What if the insulation separating cooper bus bar and panel chassis short? The 16 GFCIs 2-pole breakers to be installed won't protect the panel chassis itself. Not even if the RCBO would be put in the main panel.

This is why the RCBO needs to be put in another panel (below) connected before the main panel. And the house just happened to have redundant one in the following. I can replace this with rail DIN type. But I want to make sure the 100mA won't suddenly trip even without any leakage. I know the rest of the 16 GFCIs can trip for their respective appliances. Do you know of any equipments that can't be protected by any RCDs because they always trip? Like airconditioning units? And do you know if anyone else installed RCBO in main panel breaker or only me?

1) I cannot estimate the degree of capacitive coupling in your situation, but it will be low, because most of the capacitive coupling 'leakage' to 'ground' is from the hot conductor to the ground wire, and you don't have a ground wire and don't have circuits with only one hot conductor.

2) I do not know the best RCBO to use; I do not have extensive experience with such units. My only experience is with the ground fault relays that we use in our lab, and those are a different sort of beast; we are only protecting equipment, we are working on 'resistance grounded' systems, and the trip point is set between 1 and 5 _amps_. So I know the theory but I can't give advice on particular hardware.

3) IMHO in your situation 100mA will not trip unless there is real leakage; however as I have previously stated this is not a good way to pick a trip level. You pick the trip level based on what you wish to protect; so if you want to protect a person from shock your trip level _must_ be that of a class A GFCI, but if you want to protect equipment your trip level might be 100's of mA or even _amps_

4) In my experience, the only equipment which has lots of residual current without a true insulation failure is equipment with variable frequency drive motors. The high switching frequency is easier for capacitive coupling, and so you can see high leakage current at the switching frequency. In a residence you might see this sort of motor in a central AC unit. Anything else: window AC unit, refrigerator, bathroom exhaust fan, if it trips a GFCI then there is a real insulation failure.

5) Consider also: in your situation you don't have a 'grounding' conductor to bond the chassis of equipment and hold its voltage low in the event of leakage current. It doesn't matter if this leakage is caused by insulation failure or by the 'nature of the equipment'. If there is leakage current and you don't have good solid bonding, then you have a shock hazard.

As I have said, there is nothing inherent about how a refrigerator functions that will cause much leakage current. (My refrigerator is on a GFCI with no problems at all.) But imagine that the internet folk are right and some sort of induction in the defrost heater causes current to leak. You don't have grounding, so where does this current go??? It goes to energize the chassis of the refrigerator, meaning that the refrigerator would be a shock hazard, exactly what you want to protect against.

If there is any equipment in your home that will trip a GFCI, consider that equipment broken. If there is something in your home that cannot be replaced and cannot work on a GFCI, and you want safety, then you will have to figure out how to install grounding (which you have already said is not practicable, and so you would be stuck giving up on that piece of equipment.)

6) Finally: given your existing install without proper grounding/bonding, it is quite possible that there is already a fault in your feeder and you don't know it. With no reliable fault current path, fault currents can be quite low, and if the fault is in a conduit buried underground or in concrete there might be no place where someone could come in contact with the current and thus no noticed shocks. I would suggest that prior to installing an RCBO you have your electrician use a clamp on current meter to _measure_ if there is existing residual current.

If there is residual current (indicating a high resistance fault) then you would need to fix the problem prior to installing the RCBO.

-Jon

 

[tersh]

1) I cannot estimate the degree of capacitive coupling in your situation, but it will be low, because most of the capacitive coupling 'leakage' to 'ground' is from the hot conductor to the ground wire, and you don't have a ground wire and don't have circuits with only one hot conductor.

2) I do not know the best RCBO to use; I do not have extensive experience with such units. My only experience is with the ground fault relays that we use in our lab, and those are a different sort of beast; we are only protecting equipment, we are working on 'resistance grounded' systems, and the trip point is set between 1 and 5 _amps_. So I know the theory but I can't give advice on particular hardware.

3) IMHO in your situation 100mA will not trip unless there is real leakage; however as I have previously stated this is not a good way to pick a trip level. You pick the trip level based on what you wish to protect; so if you want to protect a person from shock your trip level _must_ be that of a class A GFCI, but if you want to protect equipment your trip level might be 100's of mA or even _amps_

4) In my experience, the only equipment which has lots of residual current without a true insulation failure is equipment with variable frequency drive motors. The high switching frequency is easier for capacitive coupling, and so you can see high leakage current at the switching frequency. In a residence you might see this sort of motor in a central AC unit. Anything else: window AC unit, refrigerator, bathroom exhaust fan, if it trips a GFCI then there is a real insulation failure.

5) Consider also: in your situation you don't have a 'grounding' conductor to bond the chassis of equipment and hold its voltage low in the event of leakage current. It doesn't matter if this leakage is caused by insulation failure or by the 'nature of the equipment'. If there is leakage current and you don't have good solid bonding, then you have a shock hazard.

In my over 1,000 relatives and friends. I haven't heard of anyone getting a shock or electrocuted. I wonder if it's because our appliances are all plastic now. What metal chassis do you use regularly in the US? The reason there is such low fatality is the reason literally no one use any grounding around the country. All haven't heard of GFCIs too. I'm just doing it just to be sure and to learn fascinating new technology.

You mentioned a lab. So you may be in a high tech facility. Can you help me think of any commercially available open neutral service detector or possible design of one using combination of RCDs (see the url in the link below). I have a single 120v apparatus in a commercial building with neutral inside. And since the utility company doesn't maintain the service neutral well because not much use it. I don't want the electricity to divert to my aircon chassis or panel chassis if the neutral service gets open or disconnected. Please see this thread and help me. http://forums.mikeholt.com/showthread.php?t=195234

If there is no solution for a detector and disconnector in case of open neutral service. Then I need to remove the only 120v item in the commercial building which is the Siemens First Surge 140,000 Surge Protector Device. It has circuits inside it that uses 120v and may be more than 5mA. Please check out the link. Many thanks for the tips below. I'll think about it while waiting words from Siemens if my Siemens GFCI (the 16 to be installed) were counterfeit.

As I have said, there is nothing inherent about how a refrigerator functions that will cause much leakage current. (My refrigerator is on a GFCI with no problems at all.) But imagine that the internet folk are right and some sort of induction in the defrost heater causes current to leak. You don't have grounding, so where does this current go??? It goes to energize the chassis of the refrigerator, meaning that the refrigerator would be a shock hazard, exactly what you want to protect against.

If there is any equipment in your home that will trip a GFCI, consider that equipment broken. If there is something in your home that cannot be replaced and cannot work on a GFCI, and you want safety, then you will have to figure out how to install grounding (which you have already said is not practicable, and so you would be stuck giving up on that piece of equipment.)

6) Finally: given your existing install without proper grounding/bonding, it is quite possible that there is already a fault in your feeder and you don't know it. With no reliable fault current path, fault currents can be quite low, and if the fault is in a conduit buried underground or in concrete there might be no place where someone could come in contact with the current and thus no noticed shocks. I would suggest that prior to installing an RCBO you have your electrician use a clamp on current meter to _measure_ if there is existing residual current.

If there is residual current (indicating a high resistance fault) then you would need to fix the problem prior to installing the RCBO.

-Jon