Converting to a TT system... possibly

[chris day]

1.25ohm external earth fault loop impedance on TN-S supply to building

Supply authority stated our only option is a TT conversion as they will not covert to PME.

What would be my best course of action when converting to a TT as the building is quite old and i do not want a 100ma main switch for diversity reasons and nuisance tripping, so Would it be suitable to convert to TT and have all final circuits in a RCBO with a board charge?

 

[Midwest]

Page 33 OSG (yellow) has an example you're suggesting, i.e. for new A3 CU's.

Wylex have just released a SPswN RCBO, and use a bespoke gland for tail entry.

 

[Octopus]

Why do you not want the 100 mA RCD as the main switch?

 

[chris day]

Thank you Midwest looking at page 33 is quite useful

on a side note i want to avoid hammering a TT rod through a gas pipe, i have never installed an Earth mat are these a viable option as the property is surrounded by soil/grass

 

[Midwest]

Never installed or seen an earth mat, guess someone here has, or perhaps ask one of the manufacturers.

Out of curiosity, why won't your DNO convert to PME?

 

[Strima]

Thank you Midwest looking at page 33 is quite useful

on a side note i want to avoid hammering a TT rod through a gas pipe, i have never installed an Earth mat are these a viable option as the property is surrounded by soil/grass

A sweep with a cat, not the feline kind, should help you avoid any other services.

SDS adapter and you can have a rod in the ground in a few seconds with little effort.

 

[The Ghost]

Why not get DNO to maintain and improve their earthing arrangement. i.e. repair their poor TN-S earth?

 

[Risteard]

SDS adapter and you can have a rod in the ground in a few seconds with little effort.

As long as it's not rocky etc.!

 

[chris day]

Out of curiosity, why won't your DNO convert to PME?[/QUOTE]

their exact words are that they are unable provide that service due to location.

 

[chris day]

Because they have simply said either convert to PME (which they wont) or convert to TT which leaves only the last option.
there is nothing else they want to do to help

 

[chris day]

What is this SDS adapter as i normally use a club hammer?

 

[Nigel]

If your Zs reading are within the maximum permitted I would not do anything personally.

 

[MDJ]

One question, will the rod be a better bet than the poor TNS earth?

 

[Nigel]

Thank you Midwest looking at page 33 is quite useful

on a side note i want to avoid hammering a TT rod through a gas pipe, i have never installed an Earth mat are these a viable option as the property is surrounded by soil/grass

We install mats regularly.

You will still need to dig down about 300mm but you will be able to CAT scan the area accurately.

The reason mats are deemed safer is that most Permit to Digs instruct you to CAT scan every 300mm. You cannot do this when driving an earth rod in.

 

[DPG]

Surely they should come out and sort their earth out.