TN-C-S (PEN) RCBOs Discussion

[Burnmenot]

I'm currently planning for a CU upgrade on the domestic premises, and following previous advice on this forum, I was told that I should consider upgrading to a Type A RCBO CU.
I have been doing a bit of reading and came across some confusing information, stating that an RCD would not work on a PEN system, RCCD was not permitted on a PEN system and consequently, RCBO would not work and it will have to have separate earth.

I believe I have a PEN system as the earth it's taken at the DSO service fuse, and I also seem to have a small green hatch on the ground for rod servicing...
I can add some photos for clarification if needed.

This is confusing to me as I do seem to have split distribution with an RCD protecting the socket rings, immersion, and boiler, and on the other side, all the light rings an RCBO for the shower.

I would appreciate any comments

 

[westward10]

Yes.

That helps who, how?

And is justified by what?

No idea what you are getting at.

 

[Risteard]

Or a reflection of very successful lobbying by the electrical industry.

Some would suggest that it has more to do with successful lobbying by the Revenue Commissioners. I'm not sure that I agree with them as it is a rather cynical view, but I suppose it's possible that there could be some truth to it.

 

[Risteard]

You'll need to consult with a reputable electrician to you, but in the U.K. that would not meet our regulations.

Old I.S. 201-4 16mm^2 T&E had a 10mm^2 protective conductor which meets the requirements for the main protective conductor (neutralising link). The newer 16mm^2 T&E (and even newer LSF version (minimum Dca, -s2, d2, a2) which needs to be used now) has a 16mm^2 protective conductor, which is also insulated.

 

[LastManOnline]

Or a reflection of very successful lobbying by the electrical industry.

I do agree that there is likely an element of that involved as well. I felt like that when the PIR, s(periodic inspection reports) were first introduced. The idea of "taking apart" a privately owned, 5 year old home by subjecting it to the same exhaustive testing as we would a newly installed electrical installation never felt right.
Its different for rented accomodation (especially student accomodation). But I still think that a 5 year old home should not require every accessory to be disconnected, inspected, IR tested etc. An experienced visual inspection combined with checking and testing of all safety devices and earthing would suffice in my opinion

 

[i=p/u]

And that's what the books tell you... you as the inspector decide..

 

[LastManOnline]

, but I have never seen the ROI as a country associated with "following orders" as one might do for, say Germany.

This came into my mind today and I had to laugh. "Following orders" is definitely more of a Germanic trait than an Irish one. However the Irish electrical system has always had a significant German input. I have learned recently that you DO NOT question the electrical regs in ROI.You "follow orders". In less than a year I have being removed from one forum, sanctioned in a second forum and politely told to "shut it" in a third forum (by fellow sparks) for doing precisely that. The German influence?? possibly

 

[nicebutdim]

This came into my mind today and I had to laugh. "Following orders" is definitely more of a Germanic trait than an Irish one. However the Irish electrical system has always had a significant German input. I have learned recently that you DO NOT question the electrical regs in ROI.You "follow orders". In less than a year I have being removed from one forum, sanctioned in a second forum and politely told to "shut it" in a third forum (by fellow sparks) for doing precisely that. The German influence?? possibly

Questions about PEN faults?

 

[LastManOnline]

Questions about PEN faults?

Yes. Among others.

 

[nicebutdim]

Yes. Among others.

I like that you're inclined to question that which doesn't sit right with you, but I can see how it might not go down well where rules are to be followed and not questioned.

Maybe those who object to your questions might ask themselves how those rules came about in the first instance...

 

[LastManOnline]

I like that you're inclined to question that which doesn't sit right with you, but I can see how it might not go down well where rules are to be followed.

I understand their reaction. What I, m inclined to do (I do the same on this forum) is sometimes to focus attention at other countries work practices and ask if " could we perhaps learn from that?" Sometimes its appreciated, sometimes it's not. My post about the shortcomings of TNC-S went down like a lead balloon. I was removed from the site. A few weeks later a newsletter from "Safe Electric" addressed the topic directly. Co-incidence?

 

[pc1966]

I too like to see how things are done elsewhere as every country's system is a mixture of good and bad, and largely not that planned either (i.e. often things had to follow on from past installations & standards).

The TN-C-S open PEN risk is something that looks like becoming a topic as more folk look to EV chargers. I suspect there won't be and change to TN-C-S usage by the DNO as it is widespread and cheap, but I think inevitably EV chargers will all have to be Zappi-like in protecting against open PEN risk without an earth rod, as driving in rods in urban areas is going to cause all sorts of practical issues and damaged utility cables/pipes.

The ROI practice of having rods for the TN-C-S earth locally makes a lot of sense, though I doubt that 1.2m rods are meaningfully low to help much. The discussed option in AM2 for our 18th to make it part of foundations makes more sense, as it could be well under 10 ohms that way, but that will take years (if ever) to make much difference considering it won't be retro-fitted to the majority of housing.

 

[LastManOnline]

I too like to see how things are done elsewhere as every country's system is a mixture of good and bad

"A mixture of good and bad" sums it up well. I like to start a discussion on the "bad" to explore how it might be improved.

I suspect there won't be and change to TN-C-S usage by the DNO as it is widespread and cheap.

No. Its here to stay. So with that in mind lets educate people about the shortcomings of the system and that could go a long way in mitigating the risks associated with it.

The ROI practice of having rods for the TN-C-S earth locally makes a lot of sense, though I doubt that 1.2m rods are meaningfully low to help much.

They will help in reducing touch voltage to some extent. What is unfortunate about them is that in almost every country that uses them (ROI, AUS, NZ etc) in their TNC-S supply system, there is this misunderstanding that the 4 foot rod is a "back up" under open PEN faults. This misinformation is widespread. I have encountered it in discussions with inspectors and educators. I, m a, little baffled by that.

. The discussed option in AM2 for our 18th to make it part of foundations makes more sense, as it could be well under 10 ohms that way,

Makes good sense.

 

[pc1966]

What is unfortunate about them is that in almost every country that uses them (ROI, AUS, NZ etc) in their TNC-S supply system

I think the USA has two rods, spaced apart (8 feet?) but again 4 foot deep is not going to give you any meaningfully low earth Ra value.

Historically the metal service pipes did give you a decent earth, and often backup connectivity between supply E (i.e. PEN) bonds, but they are of course all being converted to plastic.

 

[LastManOnline]

I think the USA has two rods, spaced apart (8 feet?) but again 4 foot deep is not going to give you any meaningfully low earth Ra value.

I stand to be corrected here but my recollection is that the Americans use as you correctly say, 2 rods, but I think they are longer than 4 feet. In any case I know they do a better job with their rods than we do.

Historically the metal service pipes did give you a decent earth, and often backup connectivity between supply E (i.e. PEN) bonds, but they are of course all being converted to plastic.

This has been the single most important factor in the introduction of our TNC-S system. I can appreciate that in the late 80,s when plastic started to replace metal services there was a major recession going on. There possibly was, nt the money to pay for anything other than TNC-S, the cheapest supply system available.