Earthing Arrangement- confused

[Freetrader]

Hi Everyone

A bit of a confusing with an earthing arrangement,

To all purposes it looks like a TNC,

Earth from MET to clamp on the supply cable coming in from the ground,

but also From MET an earth going to an earth rod just outside the house as well.

the house is not in the country, been a housing estate for the last 50+ years,

origionally corporation housing, now private since 80's.

all ideas wellcome.

 

[Lurch]

Usually just TNC with a customers rod for added protection. Remove rod and it's TNC again, the rod is for protection if the incoming earth fails or is low. Treat the installation as TT otherwise the rod is no good.

Quite common, steptoe probably done that one.

 

[Freetrader]

posted again as I ment to say TNS, but the answer is the same, thanks

 

[Andy™]

may just be an additional earth. check the sheath Ze and see what that is. this should be your main earth (TNS)

 

[steptoe]

Usually just TNC with a customers rod for added protection. Remove rod and it's TNC again, the rod is for protection if the incoming earth fails or is low. Treat the installation as TT otherwise the rod is no good.Quite common, steptoe probably done that one.

well, ummm, ahhh,

X(

check the Ra, if its good then disconnect the sheath and just use rod.

 

[Andy™]

well, ummm, ahhh, X(

check the Ra, if its good then disconnect the sheath and just use rod.

why? the sheath is in effect one big rod! if it was TNCS, then i may have agreed with it

 

[steptoe]

and what is your new combined earthing system called?

if you go by a TNS system and DNO decide to disconnect your earth sheath then your in big trouble!

and they can do this if you provide your own earth, having 2 earthing systems is not a good idea, in fact its a very bad one due to various reasons that Im not going to go into yet again on this forum,

you cant just decide to mix and match various earthing arrangements to suit yourself, use one system.

 

[steptoe]

[quote name='Andy

 

[Andy™]

there is NO SUCH THING,you should have an EARTHING CONDUCTOR , one of, not a main earth and a secondary earth.

thats very much a DIY statement having a main earth.

im not talking about the earthing conductor. im talking about the sheath being the main earth into the property.

 

[ian932]

and what is your new combined earthing system called?if you go by a TNS system and DNO decide to disconnect your earth sheath then your in big trouble!

and they can do this if you provide your own earth, having 2 earthing systems is not a good idea, in fact its a very bad one due to various reasons that Im not going to go into yet again on this forum,

you cant just decide to mix and match various earthing arrangements to suit yourself, use one system.

In the republic of Ireland if you have PME, you are required by ET101:2008 to have a earth rod with a 10mm earthwire to the baord as well.

 

[Andy™]

i dont really see a problem with a rod additional to TNS. after all, the sheath is one large rod anyway. although in reality, the sheath earth, even if failed at a joint, is usually lower resistance than a rod would be so would provide a better earth

 

[wozz]

In the republic of Ireland if you have PME, you are required by ET101:2008 to have a earth rod with a 10mm earthwire to the baord as well.

this is how i thought many countries done it.

 

[Andy™]

they have most likely though ahead for if the neutral fails....

 

[steptoe]

it takes the onus of providing an earth of the DNO and puts it on the consumer.

PME was originally only for underground supply but now even that has changed.

IMHO do whatever you want with your earth,

I really am getting to the point of not caring,

people arguing over earthing systems they dont understand, then trying to justify what they have said.

Im only giving an opinion as to what is actually safe.

go FRY as many customers as you want, but your repeat business will be rubbish.

 

[binky]

it takes the onus of providing an earth of the DNO and puts it on the consumer.PME was originally only for underground supply but now even that has changed.

IMHO do whatever you want with your earth,

I really am getting to the point of not caring,

people arguing over earthing systems they dont understand, then trying to justify what they have said.

Im only giving an opinion as to what is actually safe.

go FRY as many customers as you want, but your repeat business will be rubbish.

Calm down Steps. I have come across the same situation myself - re-wire by an apprentice or builder, and whilst my initial thoughts were 2 is better than one, I eventuallly removed rod to avoid the confusion a multiple sysytem causes. If the TN-s is good, than the rod will be doing nothing anyway, and as pointed out above, to rely on the rod you have to have a TT system set-up, not that its wildly different under new regs, but significantly different under 16th.

 

[Andy™]

it takes the onus of providing an earth of the DNO and puts it on the consumer.PME was originally only for underground supply but now even that has changed.

IMHO do whatever you want with your earth,

I really am getting to the point of not caring,

people arguing over earthing systems they dont understand, then trying to justify what they have said.

Im only giving an opinion as to what is actually safe.

go FRY as many customers as you want, but your repeat business will be rubbish.

it appears to be your way or nothing lately.

 

[steptoe]

sorry you feel like that,

but its not, not at all.

its about getting the earthing correct, and SAFE.

you can not AFAIK have two earthing systems in one installation/zone.

you either TT it or you dont.

you leave the spike in, but do all your calcs for TNS, DNO comes along, sees you have upgraded to TT, removes their cable sheath system, the last person to touch the installation is answerable for the now NON compliant TT system.

 

[Nicky Tesla]

EQUI Bond to all extraneous conductive parts, such as a service pipe or rod perhaps.

How can this be dangerous, the neutrals not connected. load of rubbishWet Fish

 

[PBC_1966]

In the republic of Ireland if you have PME, you are required by ET101:2008 to have a earth rod with a 10mm earthwire to the baord as well.

this is how i thought many countries done it.

It's certainly done that way in the U.S. The NEC requires an earth electrode connected to the neutral at the service entrance.

its about getting the earthing correct, and SAFE.you can not AFAIK have two earthing systems in one installation/zone.

you either TT it or you dont.

What is unsafe about having an extra earth electrode on a TN-S or TN-C-S system?

How is it any different - electrically speaking - from a house which still has a metallic water supply line running multiple tens of feet below ground, and which is required to be bonded?

you leave the spike in, but do all your calcs for TNS, DNO comes along, sees you have upgraded to TT,

I wouldn't call changing from TN to TT an upgrade, but still......

removes their cable sheath system, the last person to touch the installation is answerable for the now NON compliant TT system.

And who would be the last person to touch the system? The DNO, surely?

Should any DNO guy be casually disconnecting a TN earth just because he happens to see an earth rod connected to the MET?

 

[netblindpaul]

Steptoe,

I'm new to the forum, and have read several posts you have made on the merits of various earthing systems.

I don't want to get into a debate about the merits etc.

However, just a question as to how you feel it is possible for a DNO to unilaterally change a supply system, and also not comply with the ESQCR?

Surely they would be in breach of their statutory duty?

IF the DNO provide the earth via TNS/TNCS then they are then legally obliged under ESQCR to maintain it?

Are there that many examples of the failure of DNO TNCS systems that you have experienced.

Please excluding the extremely rural borderline TNCS systems that are around, where probably TT would undoubtedly be better suited.

I had a walk around my little village recently with one of our local DNO guys and we counted about 6 earthing rods apart from the local transformer (HV&LV) and the local underground stake on the other LV supply.

He also put in for another 3 or 4 that day, and this is a hamlet of less than 30 houses on the outskirts of a major city.

BTW my house is irrelevant I'm TT!

Paul