Ze 33.1 Ohms

[maharg]

I carried out some work on some circuits for a new kitchen including extending a ring mains lighting circuit and a cooker circuit.These circuits were not connected at the time and had been installed over a period of time.
Kitchen had been gutted awaiting a new kitchen.
Customer wanted me to look at the remainder of the house circuits after kitchen install, so i decided to install henley block,new CU and leave the old CU in place awaiting to test and transfer old circuits.
Altough i am sure i tested Ze before starting when I went to connect extended circuits I got 33.1 ohms.
This is a TNS system,I checked all suppliers connections for tightness.
I know that Reg 411.5.3 states that max Zs for RCD is 1667 ohms for final circuits not exceeding 32A but how does this leave me with the 40A cooker circuit.
Also how does it affect my max Zs for the 60898 breakers.

 

[Mr Mark Sparks]

if it is tns it is the dno who will rectify it they have to provide a ze of .8 max (i think)

 

[zupos40]

I carried out some work on some circuits for a new kitchen including extending a ring mains lighting circuit and a cooker circuit.These circuits were not connected at the time and had been installed over a period of time.
Kitchen had been gutted awaiting a new kitchen.
Customer wanted me to look at the remainder of the house circuits after kitchen install, so i decided to install henley block,new CU and leave the old CU in place awaiting to test and transfer old circuits.
Altough i am sure i tested Ze before starting when I went to connect extended circuits I got 33.1 ohms.
This is a TNS system,I checked all suppliers connections for tightness.
I know that Reg 411.5.3 states that max Zs for RCD is 1667 ohms for final circuits not exceeding 32A but how does this leave me with the 40A cooker circuit.
Also how does it affect my max Zs for the 60898 breakers.

I had a similar probem about 8 years ago, contacted the electricity supplier and they were able to change the service head and convert TN-S to TNC-S, my problem was earth sheath had corroded.

Another time someone had clamped the armouring, when the actual earth was a copper sheath within the armoured.

Anyway first step contact Suppliers, in the meantime connect all circuit very RCD, until you can sort out problem.

 

[maharg]

I had a similar probem about 8 years ago, contacted the electricity supplier and they were able to change the service head and convert TN-S to TNC-S, my problem was earth sheath had corroded.

Another time someone had clamped the armouring, when the actual earth was a copper sheath within the armoured.

Anyway first step contact Suppliers, in the meantime connect all circuit very RCD, until you can sort out problem.

Thanks for advise I have connected all circuits and they are RCD protected but to safeguard myself I would like to fill out EIC .
If I fill out EIC with high zs readings and comment that the Ze is high and DNO have been contacted am I covered

 

[zupos40]

Thanks for advise I have connected all circuits and they are RCD protected but to safeguard myself I would like to fill out EIC .
If I fill out EIC with high zs readings and comment that the Ze is high and DNO have been contacted am I covered

Please before completing EIC contact the technical dept / engineer at DNO for advice.

33.1 ohms is not acceptable and it well probably get worse, I would not be happy to leave the Ze as it is, if the DNO are unable to do anything or unwilling, you may have to convert installation to a TT (install your own earth electrode, either rod or plate)

Please do not leave it as it is, if the customer lost there earth and a fault occurred, it could be fatal. it could cost you 300K and 5 years for manslaughter

 

[maharg]

Please before completing EIC contact the technical dept / engineer at DNO for advice.

I have contacted DNO who will be arranging a call to premises.
I would still like to know how I safeguard my self.
This problem could be just with this adress or the whole street.
Someone with no RCD protection next door could be at risk,so by contacting EDF I acted with due diligence but should I record my readings or just wait until it gets better.
I might not be able to return to the premises for 2 or 3 days after EDF have been.

 

[zupos40]

I have contacted DNO who will be arranging a call to premises.
I would still like to know how I safeguard my self.
This problem could be just with this adress or the whole street.
Someone with no RCD protection next door could be at risk,so by contacting EDF I acted with due diligence but should I record my readings or just wait until it gets better.
I might not be able to return to the premises for 2 or 3 days after EDF have been.

You say all circuits are RCD protected and tested if you complete EIC then when EDF call and decide to change to TNCS or tell you to convert installation to a TT, your certificate will be worthless.

So if your completing generic certificate and not NIC, ECA etc numbered form then complete cert by all means, but it may be worth you writng to the customer explaining why you have not issued EIC.

Yes rest of the street could be effected, if you worried maybe pop next door and ask if you could check their supply, it may get you more work.

As long as all circuit are RCD protected your covered and you have informed client in writing about problem you be fine.