Ze test and a DNO earth block

[nickblake]

Evening chaps a periodic today walked through the front door and my concerns were were raised just glancing at the supply cable and cut out and yes my concerns were right ,and obviousley the electrical contractor never tested the supply infact the installation as this would have thrown up the fault or error , i have come across this so many times now its worrying , when you carry out a Ze test you should isolate the supply disconnect the main bond to the board then carry out your test , this install the main earth had been connected to the cutout earth block although it was obviouse it was not a TNCS but a TNS supply the wire had been cut off the TNS earth (again) and connected to the earth block which was not connected in the cutout (this was confirmed by testing the neutral to the earth block and it was open circuit) the whole house was not earthed with the bonds and all earths connected the Ze reading was 696 ohms , so redoing the test connecting to the TNS connection the reading was 0.60 ohms , then making the connection properly this dropped to 0.29 ohms . so a little message when testing or connecting your Earth bonds to the cut out earth blocks check to see if its connected first

 

[tony mc]

I had the same recently where I knew the house was PME but on doing a ZE test I got way over 300ohms.

Called the emergency line and out came the DNO who re connected the earth and neutral link.

The link was slid to one side and must of been disconnected when the new meter and tails were installed.

 

[oldtimer]

Yep totally agree I posted a while ago here and I found 2 problems ie the one below the board was about 20 years old and because there was no DNO earth the spark left the earth cable hanging the other was the DNO put a new head end in but would not put an earth in and ended up mumbling something to the house owner about it until 7 years later muggins seen it and within 5 minutes there was a 1 metre 16mm earth installed

 

[nickblake]

house holder said nothings been done in the house for the 8 years they lived there so all i can say is like you 8 years and no earth , i find it hard to belive such a simple test ,wasnt rocket science to sort out did a temp job as they are upgrading the consumer unit ,took me longer to walk to the van to get the bits than it did to do the job stupid thing is they installed the bonding to the gas and water service bit pointless in my opinion

 

[sparc]

I'd be interested to hear your views on what's going on here ... It's an upcoming job to change out CU, and I've contacted the DNO requested a new cut-out. I'm curious what the red 'clay' like material is, and whether this is something the DNO puts on. Not seen it before - doesn't look 'official'One earth (RHS) goes directly to fuse board, the other (LHS) to the MET.

 

[nickblake]

Its electrical cable putty it is a non setting insulation putty and often used to seal cut outs where you can get access to exposed parts with in the cut out via the cable entry so not to IPxx if im not mistaken

 

[Edd]

Installing an alarm system and a new CU a couple of weeks ago after the CU was installed I started testing to find 12 ohm on a tns system ( not the end of the world). called the DNO who turned up in about 2 hrs as i was clearing up (quite quick i thought) anyway he tested it and said, yep lead sheath was probley never connected out in the street, as they used wooden joiners! so he said it was dig up the street or PME the head, I said yer I think we should go with the PME..
He said as he wasnt the supplyer he couldnt and the customer would have to apply for it!!!
I told him I was tempted to do it before I had made the phone call but thought i should go through the proper chanels.
he said yer no probs you PME it and he would re seal it latter if I needed. told him i had seals and would do it myself and it was left there, he was happy I was happy customer was happy, but I was a bit confused as it took me 10 mins to PME it myself. He said he couldnt do it as he worked for a large company who check everything he does, but was happy for me to do it and even volentered to return to reseal it...
strange days we live in... and theres us worring about cutting the odd seal....

 

[sparc]

That makes sense -just thought it looked a bit 'rough and ready' to be legit! The guy at PNO said something about PME as the replacement, when they get around to it.

 

[sparc]

Installing an alarm system and a new CU a couple of weeks ago after the CU was installed I started testing to find 12 ohm on a tns system ( not the end of the world). called the DNO who turned up in about 2 hrs as i was clearing up (quite quick i thought) anyway he tested it and said, yep lead sheath was probley never connected out in the street, as they used wooden joiners! so he said it was dig up the street or PME the head, I said yer I think we should go with the PME..
He said as he wasnt the supplyer he couldnt and the customer would have to apply for it!!!
I said I was tempted to do it before I had made the phone call but thought i should go through the proper chanels.
he said yer no probs PME it and he would re seal it latter if I needed. told him i had seals and would do it myself and it was left there, he was happy I was happy customer was happy, but I was a bit confused as it took me 10 mins to PME it myself, but he said he couldnt do it as he worked for a large company who check everything he does...
strange days we live in... and theres us worring about cutting the odd seal....

I don't want to re-open the whole E54/OldAL discussion thread here, but when you say you converted it to PME yourself, can you tell me how you did that please?

 

[nickblake]

All it is is a link between the neutral and the earth block and really should only be carried out by the DNO

 

[Edd]

sure most service heads when the fuse is removed, theres a locking screw that can be loosned this allows a cover that slides off the neutral. the incoming neutral is in the bottom, the outgoing neutral is out the top, and theres a knockout at the side that allows you to tap it out and connect an earth into that same block. (16mm)
from there I take it to a MET with lable and connect my water/gas and main CU earth. if its a converted TNS system I also connect the old incomming lead sheath using the crappy bit of tinned wire you find
NOTE if its a TT system then you need to have a close look at the poles for earth stakes and crimped connections, if they are not pressent then the area is not suited to PME..

EDIT no responsability taken for info ive supplyed

 

[sparc]

Not something I'll be attempting any time soon.

I still recovering from spending half an hour reading the 'exporting PME' thread, end to end - doing in my head in the process. :dots: