TT to PME?

[RF Lighting]

I think im gonna stick with TT, its just easier!

Don't listen to the muppet show above. Bernard doesn't have a clue about earthing and bonding and john just waffles a lot and ends up confusing everyone.

Upgrading your supply to PME is by far the best option, and if this relates to your other thread, it's going to save you a whole lot of hassle trying to provide proper discrimination between the installation RCDs and the RCDs installed to protect the submain cables.

 

[xr4x4]

I think im gonna stick with TT, its just easier!

Don't listen to the muppet show above. Bernard doesn't have a clue about earthing and bonding and john just waffles a lot and ends up confusing everyone.

Upgrading your supply to PME is by far the best option, and if this relates to your other thread, it's going to save you a whole lot of hassle trying to provide proper discrimination between the installation RCDs and the RCDs installed to protect the submain cables.

Yes it does.....so..

Exactly .....!

 

[JohnW2]

Upgrading your supply to PME is by far the best option...

Given that I stand accused of confusing everyone, I perhaps should say that I probably agree. I certainly think that Bernard's concerns about adjacent properties potentially having TT & PME supplies are generally unfounded - even under the worst supply-side fault conditions, I would think that (given proper bonding in both properties) it very unlikely that so much current would be flowing through main bonds and pipework that dangerous PDs could arise between two simultaneously touchable conductors/objects.

.... and if this relates to your other thread, it's going to save you a whole lot of hassle trying to provide proper discrimination between the installation RCDs and the RCDs installed to protect the submain cables.

I guess that depends upon what you would regard as 'a whole lot of hassle'. Given that the OP has got to get rid of his up-front standard RCD if he wants to be rid of the 'nuisance trips' which are the main reason behind his OP, he's got to bypass it, replace it with a switch/isolator or replace it with a Type S RCD. I wouldn't regard any one of those much more hassle than any other - and the latter one ought to sort out the discrimination problems you mention. Even if he changes to PME, he'll have to do one of the first two of those things.

Kind Regards, John.

 

[westie101]

Amongst all of this and the can I/can't I.
We certainly do not have any record of the earthing at individual properties, nor any need to decide that if one is TT can we make an adjacent one PME.
The only requirement is that the network complies and the bonding complies.
(this excludes cases where a PME earth cannot be offered)

As for the raising of voltage on the neutral, I certainly know of no cases of injury or death as a result of what is, after all, a common issue under fault conditions.

So I wonder what all the fuss is really about

 

[RF Lighting]

I've never heard such nonsense as that of keeping PME and TT earths seperate as bernard seems so insistent on doing. Hell the DNO actually deliberately connect the CNE conductor to an earth electrode at virtually every joint they make. It just goes to further reinforce the fact that bernard does not understand earthing and bonding.

If the OP upgrades to PME then he's got a proper earth to provide fault protection to the submains allowing him to ditch all the RCDs and the nusiance tripping they could cause, and just locally RCD protect the final circuits as and when neccessary.

He can even just use PME earth to protect the SWAs and TT the outbuildings if he wants. This is a method I have used on farms before.

 

[xr4x4]

Amongst all of this and the can I/can't I.
We certainly do not have any record of the earthing at individual properties, nor any need to decide that if one is TT can we make an adjacent one PME.
The only requirement is that the network complies and the bonding complies.
(this excludes cases where a PME earth cannot be offered)

As for the raising of voltage on the neutral, I certainly know of no cases of injury or death as a result of what is, after all, a common issue under fault conditions.

So I wonder what all the fuss is really about

Is there an easy way I can find out if I can go pme?

 

[RF Lighting]

Ring up your DNO and ask!

 

[westie101]

Is there an easy way I can find out if I can go pme?

Just ring the DNO they should be able to tell you (but not immediately), I often get similar queries from our Customer Services.

 

[xr4x4]

Ring up your DNO and ask!

I don't have control over the bill payments, the owner deals with that.

Which makes it a bit complicated, they also have their heads in the clouds, which means getting any information out of them a nightmare.

 

[ricicle]

I enquired about a PME upgrade in a friends house. The DNO refused as next door would not upgrade from TT also. As afar as I'm concerned all DNOs should sing from the same hymn sheet as the laws of physics are not different across counties/areas !

 

[RF Lighting]

Mine will happily convert from TT or TN-S regardless of what the neighbours have / do.

 

[xr4x4]

The neighbouring property is a fair distance from us, so I can't see that being a problem.

 

[bernardgreen]

The neighbouring property is a fair distance from us, so I can't see that being a problem.

First define the minimum distance that will provide adequate electrical isolation between the grounds of the two propeties.

Is it dry sandy soil ( low conductivity ) or permanently moist clay ( good conductivity ) ?

If the water supply mains are metal pipes then there is a very good ground connection between the two properties. If the same branch of the network neutral supplies both properties and is grounded close to each property then that provides a low impedance route between the grounds of the two properties.

There are too many variables for a single set of regulations to cover all situations.

 

[JohnW2]

First define the minimum distance that will provide adequate electrical isolation between the grounds of the two propeties.

As I intimated in a recent message, I'm really not sure what it is that you are concerned about. Provided adequate main bonding is in place, I cannot see any scope for even remotely dangerous PDs to arise within a 'TT' property (or the nearby PME one) due to their earthing system being in continuity with the earthing system a nearby PME installation.

Given the impedance of even a very good TT electrode, the current that would flow though bonding conductors would never be anywhere near high enough to result in any significant, let alone dangerous, PDs to arise between any two touchable points in either property - no matter what the fault conditions. To all intents and purposes, the TT property would become a PME one - and, even if the PME 'earth' rose to full line potential (hence the TT 'earth' to very close to that), there would still be no dangerous PDs within either property - at least, as far as the electrical installation was concerned. The theoretical wet floors/walls etc. issue would still exist, but to no greater extent than it exists in any PME'd property.

Hence I just don't see a problem - beyond any problems you may perceive in relation to PME, per se.

Kind Regards, John.

 

[securespark]

We certainly do not have any....need to decide that if one is TT can we make an adjacent one PME.

A few years ago in Sutton (nr Macc, not Surrey) I had a terrace on TT wanting PME. UU would not do unless the whole row went PME.

Don't know if that is still the case or whether they have since changed their minds.

Have your co. changed tack recently, westie?