will piggy backing earth rods to a TNS bring the ze down?

[LlandrilloSpark]

Evening fellas

Couple of weeks ago I posted about a high ze on a TNS I found, turned out to be a homemade TNS with an earth clamp.

DNO showed up and verified it wasn't there connection, got the same reading as me (2.08ohm)

Told me I best rod(s) it to bring it down, I've already fitted RCD main switched to all 3 consumer units.

Will ridding bring it down to below 0.8?

I was suspicious about it

 

[Spazz]

Whats wrong with a reading of 2.08 or 0.8 on a TT (which ever you got)

I would be happy with that reading.

A deeper rod or piggy backing earth rods might bring it down but to be honest both of those readings are more than acceptable.

I am normally getting anything between 0.4ohms and 54ohms on TTs when I do these Council houses and there are already RCDs installed

 

[LlandrilloSpark]

TNS not TT

Reading was 2.08 should be less or equal to 0.8

 

[KevinS]

I would make it a TT system if the DNO didn't improve their end for you and not rely on them

 

[Adam]

DNO showed up and verified it wasn't there connection, got the same reading as me (2.08ohm)

If the TN-S connection is not the DNO, then it is not a TN-S installation. It is a TT, so I would install a Rod (if not already one in) and test to the ROD as a TT and install RCD protection as required.

 

[Spazz]

Like you said DNO said Rod it so no question about it TT it!

Its not suitable for a TNS or a TNC-S

Stick a rod into the ground and be done with it - if customer does not want to pay for a rod then walk away and leave the DNO to deal with it - their problem - you have reported it so your in the clear

 

[LlandrilloSpark]

If its not TNS then it's nothing then Adam!

DNO said not theirs but happy with connection!

My ultimate question is ...is there any point inserting rods?

 

[Des 56]

If the TN-S connection is not the DNO, then it is not a TN-S installation. It is a TT, so I would install a Rod (if not already one in) and test to the ROD as a TT and install RCD protection as required.

Sound advise,but I would say in this instance you don't have a Tns and you dont have a TT
If the existing supply gets altered and that earth is lost,they are unlikely to inform anyone of the change

 

[Spazz]

If you keep it as it is and go against the DNO advice and not install a rod and someone gets hurt or worse you are liable!

Cover your A*** and install a rod or walk away informing the DNO it has not been touched!

 

[LlandrilloSpark]

Well DNO engineer confirmed the TNS connection is there but obviously approx one ohm over, if I remove the TNS I won't get near the 2.08 I have now with a rod, so really speaking I should be happy with the 2.08 reading I have with the homemade TNS and the RCD protection in place.

 

[Adam]

If its not TNS then it's nothing then Adam!

DNO said not theirs but happy with connection!

My ultimate question is ...is there any point inserting rods?

Actually, it is a TT as it is.

The Earth Electrode is the sheaf of the supply cable buried in the ground.

 

[LlandrilloSpark]

Nick

DNO said to keep it!

 

[LlandrilloSpark]

Adam, if you use the sheaf it's a TNS not a TT mate

 

[bigspark17]

if the DNO have told you rod it and get it down thn theres surely saying its TT.. extra rod to get reading down.. uve done rcd's already . i belive you'll have covered yourself.!!

 

[Spazz]

Evening fellas

Couple of weeks ago I posted about a high ze on a TNS I found, turned out to be a homemade TNS with an earth clamp.

DNO showed up and verified it wasn't there connection, got the same reading as me (2.08ohm)

Told me I best rod(s) it to bring it down, I've already fitted RCD main switched to all 3 consumer units.

Will ridding bring it down to below 0.8?

I was suspicious about it

That would tell me that it was not their work!
Also Rod it so rod away.

The regs state that only one type of earth system to be installed how can you have a TT and TN-S at the same time - you cant!

Like has been said its not a TN-S nor is it a TT

There is no Earth!

 

[SPARTYKUS]

If you keep adding rods it WILL drop... Thats just simple physics. Not much! But it'd drop.

 

[Spazz]

Reg 542.2.5 states that permission from the cable owner must be sort if your using the lead sheath of that cable - unless you have it in writing I would not touch it! DNOs never give permission to anyone to do what has been done here

All your doing by leaving the earth clamp on is earthing the Lead sheath - therefore its Supplementary Bonding and not an earthing arrangement.

Also if you leave it there, you have to issue a certificate which states that it was upto regs when you last touched it! the DNO know that it was like that before the cert was issued because you told them, so they could take you to court for messing with their equipment - unless you have a letter from them (or something in writing) saying leave it in place take it off and Rod it!

 

[Deleted member 26818]

To my mind, if the DNO have not provided TN-S, then it should be treated as TT.
Added to this, the Ze value of 2.08Ω would indicate that the cable sheath is in some state of disrepair, and should be treated as unreliable as an earth source.
To my mind it would be advisable to provide an earth rod just in case the cable sheath deteriorates further.
I'd leave the current connection to the sheath as equipotential bonding.

 

[Adam]

Adam, if you use the sheaf it's a TNS not a TT mate

No disrespect, but have you checked your regs book?

I will quote from my Red Book (Greed is in van).

"542.2.1: (vi) Lead sheaths and other metal coverings of cables, where not precluded by Regulation 542.2.5"

"542.2.5: The use, as an earth electrode, of the lead sheaf or other metal covering of a cable shall be subject to all of the following conditions:

(iii) The consent of the owner of the cable shall be obtained"

I won't quote the other three, as this is the relevant one. DNO told you to keep it, so I would take that as permission.

Best Regards,

Adam

 

[oldtimer]

Never mind treating it as a TT why did the DNO not convert it to a TNCS ? or did I miss something here