What to do when faced with NO MAIN EARTH?

[1shortcircuit]

A client called to explain that the Water company have replaced a water main in the street and as a result the property earthing should be checked out.

Great, nice easy test to ensure that Ze is below specified figure for system... Mmmm, not so great? Turn up to find that the 16mm main earth from the consumer unit has been left to dangle for the last five years!

What I would like to establish here hopefully is WHAT is the best course of action?

I checked for Bonding to gas and Water and that is present in the form of 1 continuous 10mm cable not exceeding 3 metres.

The DNO have been informed and said that they can get someone out in about 2-3days after they have confirmed test results, something about if they just make the connection into the supply head the substation could blow up lol? They asked if I could do something temporary and I explained that I could but the client was not happy to relieve his wallet of said amount for the sake of a few more days considering it's been this way for 5 years already.

I couldn't test for Ze so I performed the same test but used the main earth terminal with all cpc's and bonding still connected and got a reading of 7.84 ohms, well above anything we would want but still indicating that earth was present probably in the form of the Gas/Water bonding?

What tests should I have performed??? How would you have handled this situation:thumbsup

I noticed an RCD present so I wanted to check it's operation. I plugged my tester into the downstairs ring and the RCD x1 and x5 test came back well within the specified 200ms and 40ms.

Any feedback is much appreciated.

Regards

1SC

 

[telectrix]

check for signs of TN-S ( a bit of bare conductor soldered to the sheath of the supply cable ). and is there an earth terminal alongside the cut-out. apart from that, you have to wait for DNO or rod it.

 

[1shortcircuit]

check for signs of TN-S ( a bit of bare conductor soldered to the sheath of the supply cable ). and is there an earth terminal alongside the cut-out. apart from that, you have to wait for DNO or rod it.

Thanks for your reply Tel.

Checked for TNS connection and nothing there also.

The head had 3x100A fuses and a Neutral all enclosed behind seals and no main earth terminal visible although the knockout is there ready and waiting to be punched through

I've not encountered a situation like this before. I believed that I had do9ne everything that I could but whilst driving home I found myself wondering if there was anything else other than rodding it that I could have done?

:thumbsup

 

[telectrix]

even banging a rod in may not have improved the Ze. at least with RCD protection, the installation is reasonably safe.

 

[diditrain]

Measure Ze using the neutral, then if the figure is low enough ask the DNO if it can be converted

 

[Spudnik]

You could check for PME at the incoming CU terminals.

Although its far from correct, you have done what you have been asked to do, and thats to check the main earth, which you have found dissed.

If the client is not willing to pay you to sort it, then just put your invoice in for the test, explaining EVERYTHING in detail.

Just make sure you cover yourself.

 

[1shortcircuit]

Measure Ze using the neutral, then if the figure is low enough ask the DNO if it can be converted

Even if I was aware of how to do this I'm not confident that the DNO would have agreed. I presumed this from the way they explained about the required tests and not being able to make an emergency connection as the substation may blow up?lol

You could check for PME at the incoming CU terminals.

Although its far from correct, you have done what you have been asked to do, and thats to check the main earth, which you have found dissed.

If the client is not willing to pay you to sort it, then just put your invoice in for the test, explaining EVERYTHING in detail.

Just make sure you cover yourself.

I appreciate your input Jason.

The client seemed happy

Very professional and personable, felt like JPS went the extra mile in getting the job done. Would definately recommend and use again

I think I'll give them a call in a few days to see how the situation is going:thumbsup

 

[diditrain]

Isolate the installation at the main switch and then perform a Ze but instead of putting your tester onto the earthing conductor as you do not have one you use the neutral

 

[Engineer54]

Is this an older lead sheathed cable?? If the sheath of the incoming DNO cable is available, then you can test the Ze off the lead sheath to see if it is still a viable earth path. Though to be honest, if this CU main earth cable was left hanging, it does suggest that the head was due to be changed for a PME connection, ....which never happened!!!. Perhaps that's why the RCD was installed???

As for the sub-station blowing up, You can take that with a large pinch of salt!!! lol!!!
By the sound of that, you definitly weren't talking to the right person at the DNO office...

 

[Guest123]

Doesn't seem to be much more you could have done, other than make it a TT system and leave the DNO out of it altogether.

Quite surprised they offered to come round at all, if there wasn't an existing connection they have no remit to supply you with one.

 

[1shortcircuit]

As for the sub-station blowing up, You can take that with a large pinch of salt!!! lol!!!

I'm actually washing it down with a couple of cans of Cider now lol.

Whilst I know NOTHING about the supply side of installations I did kind of gather that this was just a MASSIVE exageration lol

Is this an older lead sheathed cable??

Unfortunately not, I did suggest to the client that it appears the change has occured and then the earthing been forgotten about. Perhaps the previous owner was supposed to have rectified it and then stalled when they realised it was more cost?

Quite surprised they offered to come round at all, if there wasn't an existing connection they have no remit to supply you with one.

To be honest this could be the reason that it's been like it for the last 5 years.

Thanks for all of your posts, very much appreciated:thumbsup

1SC

 

[Engineer54]

I'm actually washing it down with a couple of cans of Cider now lol.

Whilst I know NOTHING about the supply side of installations I did kind of gather that this was just a MASSIVE exageration lol



Unfortunately not, I did suggest to the client that it appears the change has occured and then the earthing been forgotten about. Perhaps the previous owner was supposed to have rectified it and then stalled when they realised it was more cost?



To be honest this could be the reason that it's been like it for the last 5 years.

Thanks for all of your posts, very much appreciated:thumbsup

1SC

In situations like this, when your unsure of what the local earthing system is or was ...for one reason or another!! Then i would personally ask the customer if they could ask the neighbours either side if i could have a quick look at there service heads. At the very least, it would confirm one way or another, if the local DNO are providing an earthing point or not....

 

[diditrain]

Sometimes you get a really helpful person when you call the DNO. I had a similar situation the other week and when i spoke to them they were there within a few hours and converted it for free