Earthing Arrangement

[crozzer99]

Hi. After recently paying a little attention to my electrics at home and spending time writing a list of what fuse protects what in the house i have become concerned the house is not connected to earth as it should.

I know the house was at some point connected via a TT arrangement due to a spike and connection box with a cut earth cable outside the front door.

At some point the earth cable was cut (dont know when or by whom - i brought the house 2 years ago and the previous owner had no recolection of when the electrical installation was last modified)

The current arrangement, for which i will post a couple of pictures this evening, consists of a fuse carrier marked 100A (not likely) with live and neutral connecting to a 80A 100mA RCD (wylex) then continuing to the meter and radio switch arrangement for economy 7, and then to the two relevant consumer units complete with old wireable fuses.

Each CU has an earth connection to the earth block, size 4mm. There is then what looks like a 6mm which bonds the pipework in the Kitchen/Bathroom (only pipework in the house) and i would say has been installed in the last 5-10 years at most.

There is also what can only be the remanance of the old TT connection on the earth block also but this is not connected to anything else other than the earth block.

Could it be possible that the old TT connection was removed and replaced with an undersized earth bond to the pipework - the cable is bonded pretty close ie within about 1.5M of where the water supply comes into the house.

Many thanks in advance.

Anthony

 

[holmslaw]

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[JohnW2]

Each CU has an earth connection to the earth block, size 4mm. There is then what looks like a 6mm which bonds the pipework in the Kitchen/Bathroom (only pipework in the house) and i would say has been installed in the last 5-10 years at most.
There is also what can only be the remanance of the old TT connection on the earth block also but this is not connected to anything else other than the earth block.
Could it be possible that the old TT connection was removed and replaced with an undersized earth bond to the pipework - the cable is bonded pretty close ie within about 1.5M of where the water supply comes into the house.

Unfortunately, I think you need an electrician.

Not only is the connection to your pipework probably undersized (for what regulations require for 'main bonding'), and slightly too far from the point of entry of the pipe into your house (<600mm is advised), but (unless it's a private water supply, which is unlikley) the regulations do not allow reliance on water pipes for earthing (not the least because of increasing amounts of plastic pipe in supply networks) - and may not be safe. That earth block ought to be connected either to an earth terminal supplied by your electricity supplier or, if there is no such earth supplied, to the TT earth rod. An electrician would be able to determine what sort of earthing arrangement is required. Furthermore, if your water pipes are not providing an adequate earth, your current situation could potentially be very unsafe.

Kind Regards, John.

 

[crozzer99]

Unfortunately, I think you need an electrician.

I wont even begin to tell you of the other horrors i have uncovered. The sheer ignorance/stupidity of some people is quite simply unbelievable!



As i mentioned the earth connection block is connected only to the pipe work and two consumer units. Picture will follow for clarification once i get home.

Has the regs ever accepted reliance on water pipes for earthing? If so up until how long ago would you expect this method to be use? Im pretty certain one of the previous owners didnot like the earth cable being visable outside the front door so thought it a good idea to remove for aesthetics....Smart!

Thanks Holmslaw for the link. The earth bonds would be 6 and 16 respectivly then. The old cut cable to the earth rod would have been 10.


Pics following very shortly.

Thanks.

 

[JohnW2]

Has the regs ever accepted reliance on water pipes for earthing? If so up until how long ago would you expect this method to be use?

I believe so, but not for quite a long time (decades, I think) - there are those here who will tell you. I seem to recall that there was an intermediate stage when it was still allowed, but the regs contained a warning about the increasing appearance of plastic pipework. That may well have been around the 70s or thereabouts - but I might be completely wrong.

If you're thinking that the pipework connection may once have been the only (and, then, acceptable) method of earthing which has simply persisted whilst regulations have changed, then the presence of the (disconnected) TT rod would surely indicate that not to have been the case?

I look forward to seeing the piccies.

Kind Regards, John.

 

[Paul_C]

Has the regs ever accepted reliance on water pipes for earthing? If so up until how long ago would you expect this method to be use?

I believe so, but not for quite a long time (decades, I think) - there are those here who will tell you. I seem to recall that there was an intermediate stage when it was still allowed, but the regs contained a warning about the increasing appearance of plastic pipework.

That was under the 13th edition (regulation 409 for those with a copy). The use of a water pipe as the sole earthing means was disallowed completely with the issue of the 14th edition in 1966 (regulation D.34).

 

[ban-all-sheds]

The sheer ignorance/stupidity of some people is quite simply unbelievable!

//www.diynot.com/forums/viewtopic.php?t=279354

 

[crozzer99]

Pic uploaded.

JohnW2, I was thinking the other way round actually - maybe someone thought they could upgrade the equipotentiol bonding killing two birds with one stone so to say, with the thought the incomming water would provide earth thus being able to remove the bond to the earth rod (which we now know hasnt been practice since before 66)

If this is the case it is very worrying and needs sorting ASAP.

Am i likely to be able to get the REC out to provide a TN-C-S system using the neutral connector block top left of the picture? if not i guess ill have to put a new 16mm earth at the front of the house. why cant people leave things alone?

On a seperate note - the RCD you can see in the image is installed upstream of the meter. This would have been installed as a means of earth leakage protection for the likely TT system but would it also double up as a means of isolation for the property?

Thanks.

Untitled

• crozzer99
• 20 Jun 2011
• 1

 

[crozzer99]

The sheer ignorance/stupidity of some people is quite simply unbelievable!

//www.diynot.com/forums/viewtopic.php?t=279354[/QUOTE]

Gee wiz. I thought he was a wind up at first. Clearly not.

 

[JohnW2]

If this is the case it is very worrying and needs sorting ASAP.

Indeed. The chances are that (even though current regs don't allow reliance on it) the water pipe will be br providing an adequate earth, but that's not guaranteed, so it's an issue that needs urgent attention.

Am i likely to be able to get the REC out to provide a TN-C-S system using the neutral connector block top left of the picture? if not i guess ill have to put a new 16mm earth at the front of the house.

I somehow doubt that they'd be able to give you a TN-C-S supply, but others here may be able to comment. How does the supply get to your property - is it overhead?

On a seperate note - the RCD you can see in the image is installed upstream of the meter. This would have been installed as a means of earth leakage protection for the likely TT system but would it also double up as a means of isolation for the property?

It certainly could be used to isolate all power to the property, but the interesting question is why it's there. Being on their side of the meter, it was presumably installed by the DNO. I may be wrong but, as far as I am aware, the only situation in which they generally do that (and, even then, usually only temporarily) is when they are unhappy about the adequacy of the earthing. Again, others here will be able to comment further.

Kind Regards, John.

 

[westie101]

I somehow doubt that they'd be able to give you a TN-C-S supply, but others here may be able to comment

Does no harm to ask!

Being on their side of the meter, it was presumably installed by the DNO.

Far more common than you realise particularly in rural areas and/or where earthing is poor. Originally they would have been voltage operated, generally if they go faulty (or if we are doing other work) we would change them except if the customer has rewired and all circuits are protected, in this case we remove them.

 

[holmslaw]

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[JohnW2]

I somehow doubt that they'd be able to give you a TN-C-S supply, but others here may be able to comment

Does no harm to ask!

Indeed - I meant to add that, but forgot!

Being on their side of the meter, it was presumably installed by the DNO.

Far more common than you realise particularly in rural areas and/or where earthing is poor. Originally they would have been voltage operated, ....

Wasn't there a bit of an irony there, in as much as a volatge-operated ELCB (which I presume you mean) relies on some sort of earth to function.

But what of the OP's situation? If, as seems to be the case, his installation has no earth at all (other than water supply pipes) you presumably wouldn't connect a supply at all,would you? If that's the case, then I guess we have to presume that the TT electrode was actually connected when the RCD was fitted. Also, as an outsider, the 'service head' (for want of a better term!) looks all a bit 'messy' to me - maybe as a result of fitting the RCD - would a DNO leave it like that?.

Kind Regards, John.

 

[JohnW2]

Water mains can be used as earth electrodes thats why I asked the question "Is your water main a private supply?"

... and very correct were you to ask that question. As you will have seen for the same reason I wrote:

....but (unless it's a private water supply, which is unlikley) the regulations do not allow reliance on water pipes for earthing

Kind Regards, John.

 

[westie101]

But what of the OP's situation? If, as seems to be the case, his installation has no earth at all (other than water supply pipes) you presumably wouldn't connect a supply at all,would you? If that's the case, then I guess we have to presume that the TT electrode was actually connected when the RCD was fitted. Also, as an outsider, the 'service head' (for want of a better term!) looks all a bit 'messy' to me - maybe as a result of fitting the RCD - would a DNO leave it like that?.

Indeed, they were usually fitted where a TT earth existed and in older (pre 60's) installations where the earthing was to a buried service. I have also seen them used where we have a PNB service. (which can look similar to a TT installation)