Open Service Neutral GFCI/RCD Detector

[romex jockey]

In the US. It passes via soil (local electrode to pole ground rod) and via the neural conductor straight to centertap. How about in Europe. Is there country there that passes soil to soil (or TT only)? In the Philippines, since we don't use local ground rod and no ground wire to centertap. It's concrete to soil to utility pole. I wonder if this has relation to manner of death by electrocution. In the US, is electrocution mostly occur at home or outside. In our country. Even though our appliances don't have EGC. Electrocution doesn't occur from it but mostly from direct contact to live wire, either from dangling wire or defective wires. For example.

Only I have GFCI. All of them doesn't know what it does.
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Lot's of Q's & i'm probably not qualified to answer most tersh.

What i can say is, it's easy to equate your 240V , with small xformer to 120V with a lot of hot tub installs we do (if it helps)

Some are close to your description , straight 240, create 120V via internal xformer, all downstream of a 40-50A 2P gfci ....groundING conductor, no noodle.

Know that the NEC likes a LOT of grounding proximal to gfci's , how this flys in a TT system i do not know. There are some who have pointed out the Netherlands , not sure if it serves as example to the Philippen system, but what i do know is most torriods are set to milliamps , which easily can escape despite the worst of return paths...

~RJ~

 

[mbrooke]

I'd like to know what exactly Mike Holt mean in https://www.mikeholt.com/mojonewsarc...l~20020816.htm by

"If the grounded (neutral) service conductor is opened or not provided at all, objectionable neutral current will flow on metal parts of the electrical system and dangerous voltage will be present on the metal parts providing the potential for electric shock."​

​

This may help:

https://www.youtube.com/watch?v=Yg6G5VUSsWA


What they are saying is that when the neutral breaks, everything in the structure that is tied to the panel ground bar will be energized relative to the soil outside the structure (remote earth).


That voltage to the soil will vary based on two thing:

1. How well balanced your 120 volt loads are between the two hot wires, more imbalance more voltage.

2. The resistance of the ground rods. Higher resistance earth rod means higher voltage, lower resistance means lower voltage because neutral current can get back to the source easier.

Does the following scenario described what he meant. Well say you lost the neutral in your service entrance (from Hurricine, earthquake, thief, etc.). And you are staying at the third floor of your house. You turn on the 120v metal bread toaster (or any appliance). Since there is no neutral return. Then the current can't leave the main panel. Instead, it will seek the neutral bus bar to ground bus bar in your main panel and from the ground bus bar goes through the ground wire straight to your toaster metal enclosure (Egc). And when you touch the metal with bare hand standing on bare feet. Then the current would use your body as return current back to the building concrete and to utility centertap. This could happen if the service neutral got cut by accident or intentionally right?

Was this what Mike Holt meant?

100% Correct!

But here is the twist, if you bond the rebar in the concrete to the panel ground bar, you energize both the rebar and the toaster case. Because both are energized at the same equal potential, the voltage between them is actually zero volts protecting the user. This is how bonding works and why its done on pools, operating rooms, ect. But both the rebar and toaster case will still be 120 volts to the earth outside.


In any case, do not rely on bonding- someone could lean against the building while standing on soil and get hit. Key is to remove the fault no matter that scenario.

Well. In the office building with 3-wire. There is no 120v appliance except 120v Leviton surge protector connected to 240-120v step down transformer. Purpose is to take advantage of lower VPR (Voltage Protection Rating). And I'm not interested in asking the electrician to activate the ground wire as 120v anymore because of the hazard. I don't take any chances. So I'm just interested in open neutral as theoretical and for knowledge when I return to the US where neutral is used for 120v.

​

Honestly, I doubt the lower VPR makes a difference. What you are protecting against is line to line surges (over 230 volts anyways) and line to ground voltages that are MUCH higher then 120 or 230 volts. Insulation in most appliances can tolerate over 1kv before break down. Whether the MOVs are rated 120 or 230 volt line to ground will not make a difference as both will start shunning and clamping voltage well before it can damage line to ground insulation.

 

[mbrooke]

I was just perflexed by Adamjamma insistence that Europe 1P+N RCDs can't be used in the US 240v system because of some feedback in the circuit. Actually in my country these Euro models are being sold for our similarly centertapped grounded neutral 240v system. https://new.abb.com/low-voltage/products/system-pro-m/residual-current-devices/rcbo

What can cause the feedback? If I buy the ABB RCD locally and install these. The company wouldn't refund them if I keep complaining that it keeps tripping. So want to get to the bottom of this circuit feedback thing before I buy some.

Honestly, I think Adam is wrong- at least when describing "classical" RCDs. Not only that, what he is proposing is actually less safe if not rendering the system useless for its intended purpose. US GFCIs & GFPs need a good solid 120 volts to function. In a TT system the GFCI circuitry will constantly put current on the grounding system- thus energizing it. Second, if the grounding system has ground rods more then a few ohms, the correct voltage across the GFCI electronics will not me maintained during a fault leading to no operation. (A bolted fault is the electrical equivalent of shorting across the hot and neutral bar, making the voltage across the GFCI electronics near zero while the high Z earth rod does not cause enough current to flow to trip a breaker) Third in a 120/240 volt system with a broken neutral the voltage may rise above 120 volts hot to neutral destroying the GFCI circuitry. Forth, as mentioned above US GFCIs have electronics which can fail over time. Most European RCD on the other hand are a simple torioid coil and solenoid and do not have the 4 limitations listed above.


To keep it simple remember this: European RCDs are often designed with the intent of being used in a TT system for fault clearing in addition to fire and electrocution protection. On the other hand in the US GFCIs are designed only around electrocution protection and the inadvertent fire protection which they offer. TT earthing is forbidden in the NEC, and open neutrals are not given much thought- so GFCIs are not required to take any of that into account.

 

[tersh]

Honestly, I think Adam is wrong- at least when describing "classical" RCDs. Not only that, what he is proposing is actually less safe if not rendering the system useless for its intended purpose. US GFCIs & GFPs need a good solid 120 volts to function. In a TT system the GFCI circuitry will constantly put current on the grounding system- thus energizing it. Second, if the grounding system has ground rods more then a few ohms, the correct voltage across the GFCI electronics will not me maintained during a fault leading to no operation. (A bolted fault is the electrical equivalent of shorting across the hot and neutral bar, making the voltage across the GFCI electronics near zero while the high Z earth rod does not cause enough current to flow to trip a breaker) Third in a 120/240 volt system with a broken neutral the voltage may rise above 120 volts hot to neutral destroying the GFCI circuitry. Forth, as mentioned above US GFCIs have electronics which can fail over time. Most European RCD on the other hand are a simple torioid coil and solenoid and do not have the 4 limitations listed above.

What do you mean "In a TT system the GFCI circuitry will constantly put current on the grounding system- thus energizing it."? I know TT means soil return path of ground, but how could it affect the GFCI circuitry inside? The solenoid should only detect leakage in the output if one lead has current going to ground. What has this goes to do with what goes on inside the GFCI unit itself??

Remember I got the US Siemens 2-pole GFCI to use on my parents home with no local electrode grounding and no direct conductor to centertap. So it's even less than a TT system. Why would it trip the internal circuitry of the Siemens 2-pole GFCI?

​

By the way. For perspective.

my first GFCI is a local 240v receptacle

But it's made in china and the technician told me he put "with new Self-Test feature" sticker to the box to make it look like the circuit can test itself.


Then I began to doubt if it has really 5mA tripping which is a US standard and not in Europe nor even in china.


I bought this GFCI tester. But it's for 120v. I can't test if it has really 5-6mA tripping current threshold? I have concerned it has really 30mA tripping threshold.

Also it's true RCD doesn't have any receptacle but just integrated in the circuit?

This was what made me decide to get the US Siemens 240v 2-pole breaker with circuit based self test to be ensure of the quality. But the problem is protecting the panel metal enclosure itself from ground fault. It can only be clear if there is grounding connected to the utility centertap. This started all my inquiries starting what would happen if the utility transformer became floating due to pulled ground rod and it's connected to my Siemens metal enclosure. There I began to review my engineering lessons 25 years ago so as to have intelligent discussion with different engineering professionals.


My parents will keep opening the Siemens metal case to press reset for any nuisance tripping, that is why I want it to be grounded.

But with all the complications of grounding the enclosure. If I can just test the Meiji and sure it has 5mA tripping then maybe I can return the 6 pcs of Siemens GFCI breakers esp. if they would issue a recall for the mismatched spring clips and bus bar stab (with huge gaps) and I'd use the empty panel metal chasses to put my clothes or things and sell the bus bar basepan at ebay. Lol.

To keep it simple remember this: European RCDs are often designed with the intent of being used in a TT system for fault clearing in addition to fire and electrocution protection. On the other hand in the US GFCIs are designed only around electrocution protection and the inadvertent fire protection which they offer. TT earthing is forbidden in the NEC, and open neutrals are not given much thought- so GFCIs are not required to take any of that into account.

 

[tersh]

What do you mean "In a TT system the GFCI circuitry will constantly put current on the grounding system- thus energizing it."? I know TT means soil return path of ground, but how could it affect the GFCI circuitry inside? The solenoid should only detect leakage in the output if one lead has current going to ground. What has this goes to do with what goes on inside the GFCI unit itself??

Remember I got the US Siemens 2-pole GFCI to use on my parents home with no local electrode grounding and no direct conductor to centertap. So it's even less than a TT system. Why would it trip the internal circuitry of the Siemens 2-pole GFCI?

​

By the way. For perspective.

my first GFCI is a local 240v receptacle

But it's made in china and the technician told me he put "with new Self-Test feature" sticker to the box to make it look like the circuit can test itself.


Then I began to doubt if it has really 5mA tripping which is a US standard and not in Europe nor even in china.


I bought this GFCI tester. But it's for 120v. I can't test if it has really 5-6mA tripping current threshold? I have concerned it has really 30mA tripping threshold.

Also it's true RCD doesn't have any receptacle but just integrated in the circuit?

This was what made me decide to get the US Siemens 240v 2-pole breaker with circuit based self test to be ensure of the quality. But the problem is protecting the panel metal enclosure itself from ground fault. It can only be clear if there is grounding connected to the utility centertap. This started all my inquiries starting what would happen if the utility transformer became floating due to pulled ground rod and it's connected to my Siemens metal enclosure. There I began to review my engineering lessons 25 years ago so as to have intelligent discussion with different engineering professionals.


My parents will keep opening the Siemens metal case to press reset for any nuisance tripping, that is why I want it to be grounded.

But with all the complications of grounding the enclosure. If I can just test the Meiji and sure it has 5mA tripping then maybe I can return the 6 pcs of Siemens GFCI breakers esp. if they would issue a recall for the mismatched spring clips and bus bar stab (with huge gaps) and I'd use the empty panel metal chasses to put my clothes or things and sell the bus bar basepan at ebay. Lol.

I just found out the only locally available GFCI called Meiji is just a generic OEM GFCI product made in china sold elsewhere too under different labels. It has no UL listing or any kind of listing (not even CE). See the product advertised in the US:


http://www.internationalconfig.com/icc6.asp?item=74900-RCDS

So let's test it if it's really 6mA tripping threshold. This is an international product. So if it has much higher tripping. At least it can help worldwide customers be aware. Anyone has experiences with made in china GFCI/RCD? Do you believe it can have 5mA tripping when RCD in Europe have 30mA tripping threshold?

 

[RumRunner]

Myspark. I found out there are RCDs that can open when the source lost its power. For example. Read this:

Therefore, the open service neutral detector can indeed work using RCDs that open from power failure.

I love the tenacity.


​

On the second paragraph of my post (see post #31 ) that says: “instance you cut the wire. . . . the power is lost.”. I also said that for the RCD to function and do usable work—it has to have an inductor –this is the most important component of the RCD.


​

According to Faraday, if you pass current through an inductor it stores energy in the form of magnetic field. The value of this stored energy depends on the size of the inductor as well as the current flowing through it.


​

He came up with the formula: L= flux/current.


​

Where L is expressed in Henry . The value of which is dependent upon current.​

Unlike capacitors, INDUCTORS don't like change. . . it kind of fights back in the form of back EMF.

​

It is during this back EMF event that cause a delay in the conduction of I. Current lags by 90 degrees over voltage.

Recall the mnemonic CIVIL in the early days. In an inductive circuit (L)-- the current (I) leads the voltage (V).


​

For years, I found this memory aid to be really helpful in designing electronic control circuits until another Boston U student came up with “ELI the ICEman” mnemonic. So now, I'm using this aid more often. I've also posted about this memory aid in the past in this forum. You can probably dig it up from archives.


​

I just mentioned the CIVIL mnemonic since you mentioned that you've been out of the arena for over two decades. LOL​

It is this discovery of Faraday that was taken advantage of by electronics and electrical engineers.


​

It is also used in preserving data in a memory chip for computers in keeping the BASIC INPUT OUTPUT (BIOS) intact when we power off the computer. Some have an auxiliary rechargeable battery.


​

Without it we would be reloading the BIOS every time we restart.

​

So, needless to say, there is stored energy in an inductor that you can use to trigger a transistor gate, an annunciator, open a circuit-- or give out a warning signal that will tell an operator that something needs attention.
​

 

[mbrooke]

What do you mean "In a TT system the GFCI circuitry will constantly put current on the grounding system- thus energizing it."?

I'm thinking of a 120/240 volt 2 pole GFCI applied to the Philippine system operating in TT. The neutral wire from the breaker if connected to the ground bar will put current on the grounding system.

I know TT means soil return path of ground, but how could it affect the GFCI circuitry inside? The solenoid should only detect leakage in the output if one lead has current going to ground. What has this goes to do with what goes on inside the GFCI unit itself??

Remember I got the US Siemens 2-pole GFCI to use on my parents home with no local electrode grounding and no direct conductor to centertap. So it's even less than a TT system. Why would it trip the internal circuitry of the Siemens 2-pole GFCI?

​

What are you doing with the neutral lead from the GFCI breaker? It needs a stable 120 volt source.

By the way. For perspective.

my first GFCI is a local 240v receptacle

But it's made in china and the technician told me he put "with new Self-Test feature" sticker to the box to make it look like the circuit can test itself.


Then I began to doubt if it has really 5mA tripping which is a US standard and not in Europe nor even in china.

That will do fine. The residual current circuit is powered across the line at 240. No need for 120- so you are good.

I bought this GFCI tester. But it's for 120v. I can't test if it has really 5-6mA tripping current threshold? I have concerned it has really 30mA tripping threshold.

Also it's true RCD doesn't have any receptacle but just integrated in the circuit?

Not sure what you are asking here. You can get 30ma RCD receptacles as well as 30ma RCDs and RCBOs.

This was what made me decide to get the US Siemens 240v 2-pole breaker with circuit based self test to be ensure of the quality. But the problem is protecting the panel metal enclosure itself from ground fault. It can only be clear if there is grounding connected to the utility centertap. This started all my inquiries starting what would happen if the utility transformer became floating due to pulled ground rod and it's connected to my Siemens metal enclosure. There I began to review my engineering lessons 25 years ago so as to have intelligent discussion with different engineering professionals.


My parents will keep opening the Siemens metal case to press reset for any nuisance tripping, that is why I want it to be grounded.

But with all the complications of grounding the enclosure. If I can just test the Meiji and sure it has 5mA tripping then maybe I can return the 6 pcs of Siemens GFCI breakers esp. if they would issue a recall for the mismatched spring clips and bus bar stab (with huge gaps) and I'd use the empty panel metal chasses to put my clothes or things and sell the bus bar basepan at ebay. Lol.

That Siemens breaker will not work. You need a 120 volt source. I'm guessing a transformer, but it gets more complicated then it needs to be with say a European RCD that does not need 120 volts. Actually, you can get a plastic RCD enclosure, run the service conductors to that and then the distribution panel.

Also, can I be honest? Why is that so many homes in the Philippines do not have a neutral? The Philippine Electrical Code is based on the NEC, which does not allow TT earthing or the absence of a service neutral in a grounded system.

 

[mbrooke]

I just found out the only locally available GFCI called Meiji is just a generic OEM GFCI product made in china sold elsewhere too under different labels. It has no UL listing or any kind of listing (not even CE). See the product advertised in the US:


http://www.internationalconfig.com/icc6.asp?item=74900-RCDS

So let's test it if it's really 6mA tripping threshold. This is an international product. So if it has much higher tripping. At least it can help worldwide customers be aware. Anyone has experiences with made in china GFCI/RCD? Do you believe it can have 5mA tripping when RCD in Europe have 30mA tripping threshold?

Well, how much are you protecting? If you want to protect the main panel, then 30ma might be to low and cause nuisance tripping. In Europe where a main RCD was used, often the rating started at 100ma, often 500ma. Now a sub main approach is typically used, so 30ma is usually fine for protecting a few circuits at once.

 

[tersh]

…

That Siemens breaker will not work. You need a 120 volt source. I'm guessing a transformer, but it gets more complicated then it needs to be with say a European RCD that does not need 120 volts. Actually, you can get a plastic RCD enclosure, run the service conductors to that and then the distribution panel.

Also, can I be honest? Why is that so many homes in the Philippines do not have a neutral? The Philippine Electrical Code is based on the NEC, which does not allow TT earthing or the absence of a service neutral in a grounded system.

The Siemens breaker works by using small autotransformer to power the 120v circuitry. Someone familiar with Siemens shows how:

Please give technical reasons why it couldn't work.

Between using a china mode GFCI receptacle and the Siemens, which would you trust and use? I chose the Siemens. But I had problem now trying to protect Siemens panel metal enclosure itself which we don't have neutral or ground wire direct to the utility transformer centertap.

As I have said. We don't have ground wire at almost all homes because all our appliances don't have any EGC. For example this microwave oven has no EGC so all contractors just omit adding the third wire:

 

[mbrooke]

The Siemens breaker works by using small autotransformer to power the 120v circuitry. Someone familiar with Siemens shows how:

Please give technical reasons why it couldn't work.

Ok, in that case it will work. But I would still use a European RCD:

As they have no electronics which can fail.

US GFCIs are basically a backup to an EGC, while in your case the GFCI is the EGC. Meaning that it can not fail under any condition.

Between using a china mode GFCI receptacle and the Siemens, which would you trust and use? I chose the Siemens. But I had problem now trying to protect Siemens panel metal enclosure itself which we don't have neutral or ground wire direct to the utility transformer centertap.

Honestly I do not know of the quality of the receptacle so I would not know. Regarding the panel potentially becoming live do this:

Running the main supply into the RCD enclosure, and then to the panel:

The plastic will prevent the RCD enclosure from becoming live for an internal fault while providing RCD protection for the metal breaker box and everything thereafter.

As I have said. We don't have ground wire at almost all homes because all our appliances don't have any EGC. For example this microwave oven has no EGC so all contractors just omit adding the third wire:

Understandable, in the US we have 2 prong plugs on metal framed appliances such as toaster ovens. However, per the Philippine electrical code, you still need a service neutral. Yes it may not be used for much but code still requires it.

 

[Sahib]

Ok, in that case it will work. .

The 240V to 120V step down is for control circuitry of the GFCI. But during ground fault, the GFCI may need to open load circuit conductors with 240V between them. The GFCI may not be rated for doing that.

 

[mbrooke]

The 240V to 120V step down is for control circuitry of the GFCI. But during ground fault, the GFCI may need to open load circuit conductors with 240V between them. The GFCI may not be rated for doing that.

It should be fine considering that its a 2 pole unit, a tripping of one pole should also trip the other resulting in equal or near equal sharing of interrupting distance across the 2 poles.

 

[tersh]

Ok, in that case it will work. But I would still use a European RCD:

As they have no electronics which can fail.

Why doesn't the European RCD contain any electronics?? How is that possible? What would it take for the US GFCI not to contain electronics too.

US GFCIs are basically a backup to an EGC, while in your case the GFCI is the EGC. Meaning that it can not fail under any condition.











Honestly I do not know of the quality of the receptacle so I would not know. Regarding the panel potentially becoming live do this:

Running the main supply into the RCD enclosure, and then to the panel:

The plastic will prevent the RCD enclosure from becoming live for an internal fault while providing RCD protection for the metal breaker box and everything thereafter.




Understandable, in the US we have 2 prong plugs on metal framed appliances such as toaster ovens. However, per the Philippine electrical code, you still need a service neutral. Yes it may not be used for much but code still requires it.

My electricians are not familiar with them so I won't install any of it. In fact. I may no longer install the Siemens and return them and no longer install the GFCI receptacle too. The problem is my parents having to press reset button (it's dangerous touching the receptacle). They live 80 years on appliances and houses without any grounding. So maybe there is a hidden safety in it. Right now I'm just trying to understand all this for stock knowledge for future references.

 

[tersh]

Well, how much are you protecting? If you want to protect the main panel, then 30ma might be to low and cause nuisance tripping. In Europe where a main RCD was used, often the rating started at 100ma, often 500ma. Now a sub main approach is typically used, so 30ma is usually fine for protecting a few circuits at once.

Brooke. How many percentage of people in europe really use RCBO in their main panel? It would shut down the entire house electricity if something leaks. Won't this be very inconvenient when you were in middle of bath and all power turns off and you have to come downstair naked and wet to reset it (and dangerous)?

In case you missed this sentence typed in middle of last message. Why doesn't the European RCD contain any electronics?? How is that possible? What would it take for the US GFCI not to contain electronics too.​

 

[mbrooke]

Brooke. How many percentage of people in europe really use RCBO in their main panel? It would shut down the entire house electricity if something leaks. Won't this be very inconvenient when you were in middle of bath and all power turns off and you have to come downstair naked and wet to reset it (and dangerous)?

Only about 5-10% I'd say use RCBOs- the rest rely on either a main RCD or sub-main RCD.

Inconvenient yes, but the benefit of electrocution and fire protection is seen as outweighing the risk of losing some or all the circuits in a home.

FWIW in new installs a single main RCD is rare, in most cases its two or more submains with lights on one submain and sockets on another in any given room- that so if a leak occurred the entire room does not loose power.

In case you missed this sentence typed in middle of last message. Why doesn't the European RCD contain any electronics?? How is that possible? What would it take for the US GFCI not to contain electronics too.
​

Its another way of designing an RCD. Higher ma (30 instead of 5ma), room for a big coil and a low force trip mechanism make it possible. Think of it as analog vs digital.

 

[mbrooke]

Why doesn't the European RCD contain any electronics?? How is that possible? What would it take for the US GFCI not to contain electronics too.

A redesign in the unlatching mechanism and a higher ma threshold perhaps.

My electricians are not familiar with them so I won't install any of it. In fact. I may no longer install the Siemens and return them and no longer install the GFCI receptacle too. The problem is my parents having to press reset button (it's dangerous touching the receptacle). They live 80 years on appliances and houses without any grounding. So maybe there is a hidden safety in it. Right now I'm just trying to understand all this for stock knowledge for future references.

Not much to get confused with. Its just a box and RCD- easy to figure out.

I'd still install something. Anything. It can save a life or prevent a fire. In Thailand where 230 volt Line-neutral without ground was and often still is the norm, GFCIs have been used since the 70s as the form of electrocution protection. Usually installed at the service right after the meter.

 

[tersh]

Only about 5-10% I'd say use RCBOs- the rest rely on either a main RCD or sub-main RCD.

Where do you live, UK? What is the advantage of using RCBO in main panel or RCD in main breaker? How often they trip and bring down the entire house power supply and what is often the cause of the tripping? Just nuisance tripping or inductor radiating away the current?

Inconvenient yes, but the benefit of electrocution and fire protection is seen as outweighing the risk of losing some or all the circuits in a home.

FWIW in new installs a single main RCD is rare, in most cases its two or more submains with lights on one submain and sockets on another in any given room- that so if a leak occurred the entire room does not loose power.



Its another way of designing an RCD. Higher ma (30 instead of 5ma), room for a big coil and a low force trip mechanism make it possible. Think of it as analog vs digital.

You can design a low force trip mechanism without using any circuit? How? Hmm.. how many percentage of RCDs use no electronic and how many percentage (estimate) use electronics? Which is more expensive?

 

[mbrooke]

My electricians are not familiar with them so I won't install any of it. In fact. I may no longer install the Siemens and return them and no longer install the GFCI receptacle too. The problem is my parents having to press reset button (it's dangerous touching the receptacle). They live 80 years on appliances and houses without any grounding. So maybe there is a hidden safety in it. Right now I'm just trying to understand all this for stock knowledge for future references.

I'm sure its been so for 80 years. As has been many wrong or incorrect things within the human race. At one point most of the world, if not all of it had no grounding or RCDs because the dangers of electricity were not yet well understood. Grounding came about to solve the problems of people being killed from energized; and where grounding could not be easily be implemented the GFCI/RCD took over. Contrary to popular belief the GFCI has little to do with water. It was developed as another means of providing electrocution protection where EGCs did not exist or became easily compromised- as was the case with millions of 2 prong metal framed tools in the US. Damp and exterior locations got them first because this was where skin resistance was most likely to be the lowest. Countries like the UK where 3 prong plugs were everywhere since the 40s ended up with RCDs in the late 90s, while developing countries like Asia and the US where 2 prongs were still king started with RCDs in the early 70s.

In other words its two different ways of doing the same thing and that is protecting people from energized frames.


Of course today both are being mandated simultaneously in developed countries giving overlapping protection against electrocution (failure of anyone is covered by the other) and the fire protection given by RCDs.

 

[mbrooke]

Where do you live, UK? What is the advantage of using RCBO in main panel or RCD in main breaker?

RCBO is the best but most expensive. It saves on space slot wise. A ground fault only trips that circuit. Easier wiring in the panel board.


RCD on the other hand is cheaper by protecting multiple circuits but a fault on one circuit takes out others.

How often they trip and bring down the entire house power supply and what is often the cause of the tripping? Just nuisance tripping or inductor radiating away the current?

If designed right, meaning you watch the circuit length and the total number of circuits on the RCD relative to its tripping threshold nuisance tripping is very rare.

You can design a low force trip mechanism without using any circuit? How? Hmm.. how many percentage of RCDs use no electronic and how many percentage (estimate) use electronics? Which is more expensive?

Yup. A bit of a push and the spring does the rest of the unlatching and contact opening.


I'd say about 96% of 30ma and over RCDs in Europe have no electronics. The prolification of TT earthing may be behind it.

 

[tersh]

RCBO is the best but most expensive. It saves on space slot wise. A ground fault only trips that circuit. Easier wiring in the panel board.

RCD on the other hand is cheaper by protecting multiple circuits but a fault on one circuit takes out others.

If designed right, meaning you watch the circuit length and the total number of circuits on the RCD relative to its tripping threshold nuisance tripping is very rare.

Yup. A bit of a push and the spring does the rest of the unlatching and contact opening.

I'd say about 96% of 30ma and over RCDs in Europe have no electronics. The prolification of TT earthing may be behind it.

Why is TT common in Europe? Are they saving on transformer grounding conductor? Or why didn't they ground one leg (of the two hots) to become the neutral?

In my country. Since 99.99% of homes don't have local grounding electrode and no ground wire direct to transformer, then it's like we are also TT. Or what do you refer to those without even local grounding electrode (are these installed in all homes in Europe with TT transmission system?).