Earth Protection

[hapihari]

I am informed that as my electric incoming mains is a TNS type (cables metal sheath), as opposed to a modern PME (earth to neutral connection) I should get an earth rod and main RCD incommer fitted.
Is this correct?

 

[westie101]

RCD always a good idea whatever the supply type, earth rod, not needed

 

[EFLImpudence]

Do you mean the sheath has failed?

 

[GaryMo]

Sounds like somebody is getting mixed up with a TT system.

 

[RF Lighting]

It's never a good idea to have an RCD incommer, as a single fault will leave the entire installation with no power.

 

[hapihari]

Do you mean the sheath has failed?

No, but I see what youre getting at thanks, a rod could be used as a corrective proceedure if it had failed!

 

[ricicle]

Do you mean the sheath has failed?

No, but I see what youre getting at thanks, a rod could be used as a corrective proceedure if it had failed!

Or PME if available.

 

[westie101]

If you have a TN-S earth and it fails, it is (in theory and up here anyway) up to the DNO to maintain it. We spend a good part of last week tracing and fixing a high reading to one house. Turned out it was in the "T" joint feeding the property, trouble was it was 2m deep and right in front of a driveway!

 

[PrenticeBoyofDerry]

If you have a TN-S earth and it fails, it is (in theory and up here anyway) up to the DNO to maintain it.

What if you have a TN-S arrangement and the earthing conductor is shot, do the DNO in theory or reality maintain that?

 

[PrenticeBoyofDerry]

I am informed that as my electric incoming mains is a TNS type (cables metal sheath), as opposed to a modern PME (earth to neutral connection) I should get an earth rod and main RCD incommer fitted.
Is this correct?

If your earthing arrangement is getting good Ze readings why would you?
So short answer to your question

Is this correct?

no!

 

[hapihari]

It's never a good idea to have an RCD incommer, as a single fault will leave the entire installation with no power.

thanks, you got me thinking now.
I have often pondered the pros and cons of this, and I think I would prefer the total safety of everything rcd protected and risk full blackouts rather than any of my family being on the receiving end of a live fault that doesn't disconnect.
I expect it would be expensive, but is there any reason why you couldnt fit a rccd or rcbo on each circuit to keep the protection level while not risking total loss?

 

[RF Lighting]

If you have a TN-S earth and it fails, it is (in theory and up here anyway) up to the DNO to maintain it.

What if you have a TN-S arrangement and the earthing conductor is shot, do the DNO in theory or reality maintain that?

Depends what you class as 'shot'

If the Ze is high then they will repair for free. I've had 3 so far this year which the DNO have been faultless at attending quickly and carrying out the repair.

If it's an old cast iron cutout with a 2.5mm² earth then I would expect them to upgrade all that equipment for free as well.

If it's just tatty then they might, they might not. It will be upto the DNO engineers discression.

 

[RF Lighting]

It's never a good idea to have an RCD incommer, as a single fault will leave the entire installation with no power.

thanks, you got me thinking now.
I have often pondered the pros and cons of this, and I think I would prefer the total safety of everything rcd protected and risk full blackouts rather than any of my family being on the receiving end of a live fault that doesn't disconnect.
I expect it would be expensive, but is there any reason why you couldnt fit a rccd or rcbo on each circuit to keep the protection level while not risking total loss?

No reason at all, that is the best soloution if you can afford it. RCBOs have come down a lot in price the last few years and are now a viable option for standard domestic installs.

The other option is a dual RCD setup where you have two RCDs, with each RCD protecting half the istallation, so in the event of a fault you are not left completely wihtout electricity. It's not brilliant but is (just) compliant with the regs. More of a trade off between best soloution and most cost effective soloution.

 

[hapihari]

It's never a good idea to have an RCD incommer, as a single fault will leave the entire installation with no power.

thanks, you got me thinking now.
I have often pondered the pros and cons of this, and I think I would prefer the total safety of everything rcd protected and risk full blackouts rather than any of my family being on the receiving end of a live fault that doesn't disconnect.
I expect it would be expensive, but is there any reason why you couldnt fit a rccd or rcbo on each circuit to keep the protection level while not risking total loss?

No reason at all, that is the best soloution if you can afford it. RCBOs have come down a lot in price the last few years and are now a viable option for standard domestic installs.

The other option is a dual RCD setup where you have two RCDs, with each RCD protecting half the istallation, so in the event of a fault you are not left completely wihtout electricity. It's not brilliant but is (just) compliant with the regs. More of a trade off between best soloution and most cost effective soloution.

Thanks very much, excellent advice. I shall go with one of these options, safe household - happy Dad! Cheers.

 

[PrenticeBoyofDerry]

Depends what you class as 'shot'

Case in question: Earthing Conductor has been cut back due to damage or corrosion, hard to say which. So the earthing conductor at present is about 30mm long and stripped bare of the incoming supply and extending using MET to fuse box. The Earthing conductor is a solder joint to the incoming supply sheath.
Ze is coming at 0.06Ω

If it's an old cast iron cutout with a 2.5mm² earth then I would expect them to upgrade all that equipment for free as well.

It's 6.00mm and the metering company and DNO have quoted in the region of £160+VAT to upgrade.

If it's just tatty then they might, they might not. It will be upto the DNO engineers discression.

I refer to the above information

They have offered me PME but why would I prefer a PME to a TN-C as the Ze is generally lower?