no earth

[GLENNSPARK]

If he gives me a good earth I'll have a go!

earth or girth?

 

[trev]

This thread is rapidly going down hill, not that it was ever up hill

 

[njh]

Just a bit of information picked up today, just finished a new build in the middle of nowhere and had supplier out to provide new supply, all overheads so presumed I would need earth rods, all installed ready, engineer turned up dropped an earth loop on and stuck a cut out with earth terminal, when questioned on this he said as long as they get a reading less than 0.4 ohms they automatically put a cut out with earth terminal. Not sure if this is everywhere or just regional. Waste of earth rods and time but will know better next time.

 

[Guitarist]

Overhead doesn't mean it can't be PME'd... But I guess you know that now

 

[Engineer54]

Just a bit of information picked up today, just finished a new build in the middle of nowhere and had supplier out to provide new supply, all overheads so presumed I would need earth rods, all installed ready, engineer turned up dropped an earth loop on and stuck a cut out with earth terminal, when questioned on this he said as long as they get a reading less than 0.4 ohms they automatically put a cut out with earth terminal. Not sure if this is everywhere or just regional. Waste of earth rods and time but will know better next time.

Wrong!! it was a very worthwhile, and certainly not a waste of time on your part!! It is always a good idea to have a local earth rod on a PME earth connection, especially if it's around the 20 ohms mark!! Many European countries insist on a local earth rod at all PME supplied installations!!

 

[GLENNSPARK]

Wrong!! it was a very worthwhile, and certainly not a waste of time on your part!! It is always a good idea to have a local earth rod on a PME earth connection, especially if it's around the 20 ohms mark!! Many European countries insist on a local earth rod at all PME supplied installations!!

yep...better than just relying on extranious should the neutral go floating...

 

[Geordie Spark]

When I tested my home installation a few weeks ago out of curiousity I found the Ra to be fairly pants (by which I mean 'not good', not a pair of pants buried and connected to the earthing conductor, like GlennSparks tractor engine) around 120 ohms, but with all the bonding (gas and water) and the bent copper pipe with an earth connected to it, I got 0.something ohms instead. I know technically I should try to get the twig itself a bit better, but with a reading like that I'm not sure I'll bother! One day I will test the bent copper pipe that is hammered into the ground under the house on its own and see what reading that gives.

I needed a temporary rod and used a scrap bit of 15mm copper pipe about 4 feet long which I hammered into the lawn. I was quite surprised to get an Ra of 80 Ohms without really trying. I was expecting it to be higher.

 

[Stroppy]

Your down to less than an ohm on your bonded pipe work?? lol!! Sorry i find that extremely hard to believe, in fact i'll go as far as saying, i don't believe it!!!!!!! So why is your earth rod only giving you an Ra of 120 ohms??

Hmm, maybe I'm doing something wrong. As I'm at a bit of a loose end this morning I think I'll have another go.

 

[Stroppy]

It is always a good idea to have a local earth rod on a PME earth connection, especially if it's around the 20 ohms mark!! Many European countries insist on a local earth rod at all PME supplied installations!!

Hence the 'ME' part of PME.

 

[Stroppy]

Your down to less than an ohm on your bonded pipe work?? lol!! Sorry i find that extremely hard to believe, in fact i'll go as far as saying, i don't believe it!!!!!!! So why is your earth rod only giving you an Ra of 120 ohms??

Ok, just done another test, and here are my results. Please tell me if I am doing something wrong.

Measuring Loop impedence L->PE with my probes on the tails going into the RCD for L and N, and the PE croc clip on the rod's earth cable disconnected from the MET I get 134 ohms. I put this bad reading down to it being an ancient thin twig you I can easily pull in and out of the ground by hand, and what looks like a very old 4mm earth conductor.

Measuring as above with the PE croc clip on the bond cable (which remember also has the buried copper pipe on it), I get 0.35 ohms (PFC 574A). I put this down to the copper in the hard clay earth underneath the house, metal gas pipe buried in the earth, and the fact that I am about 200 metres from the transformer. (just walked to the transformer and it is 173 paces with my little dwarf-legs )

 

[Des 56]

Its a long thread to read the full story
You have a high reading on your rod and have metal service pipes which gives a low Zs when connected

I know you say the transformer is nearby,is next door Pme ?

 

[Stroppy]

Thanks for the confirmation, that's what I thought. I'm fairly sure none of my neighbours are PME - certainly one side isn't as I've seen the installation.

I've sort of hijacked this thread. My story starts with this: http://www.electriciansforums.net/e...trical-forum/75022-no-earth-5.html#post751011

To which Eng54 replied:

Your down to less than an ohm on your bonded pipe work?? lol!! Sorry i find that extremely hard to believe, in fact i'll go as far as saying, i don't believe it!!!!!!! So why is your earth rod only giving you an Ra of 120 ohms??

 

[Engineer54]

Ok, just done another test, and here are my results. Please tell me if I am doing something wrong.

Measuring Loop impedence L->PE with my probes on the tails going into the RCD for L and N, and the PE croc clip on the rod's earth cable disconnected from the MET I get 134 ohms. I put this bad reading down to it being an ancient thin twig you I can easily pull in and out of the ground by hand, and what looks like a very old 4mm earth conductor.

Measuring as above with the PE croc clip on the bond cable (which remember also has the buried copper pipe on it), I get 0.35 ohms (PFC 574A). I put this down to the copper in the hard clay earth underneath the house, metal gas pipe buried in the earth, and the fact that I am about 200 metres from the transformer. (just walked to the transformer and it is 173 paces with my little dwarf-legs )

Metal service pipes are not laid into the ground bare, they will have some form of protective wrapping/coating on them to prevent premature corrosion!! Unless there is some sort of bonding connection from the DNO's Transformer (which is possible but unlikely) there would be little chance of seeing such a low value. Or as has been suggested, a neighbour has had their installation PME'd (legally or illegally) and your picking up their bonded metal pipework Check with the DNO, if a PME connection is available to you!! ...

Have you tried Loop testing the individual incoming service pipes to see what they are giving you? or loop testing the MET without the earth rod connected?? lol!!

 

[GLENNSPARK]

Its a long thread to read the full story
You have a high reading on your rod and have metal service pipes which gives a low Zs when connected

I know you say the transformer is nearby,is next door Pme ?

hmm...well lets face it des...he should know that relying on extranious to bring down external loop isn`t on is it
we know this happens due to parallell paths but he should know the whole idea of doing a Ze in the first place...
if he cant fathom that one...then he`s no business testing ...has he...

 

[Stroppy]

My gas pipe is definitely straight in the ground, as I can see it - its an ancient iron/steel thing that disappears into the earth. Anyway, I disconnected the bond from the gas pipe and still got 0.46, but then it ocurred to me: as the pipe is connected to appliances which have their metalwork earthed, am I not getting a parallel path through their CPC's? I'm not going to the trouble of disconnecting those, or the bonds on the water pipe or central heating as they are under the floor and a pain in the arse to get to. I'm getting more confused about this by the minute!

The more I think about it I think it is the gas service, as (a) it is a metal pipe going straight into the ground, and (b) the gas-main in the road goes right past the transformer within about 2 metres of it.

Testing the MET without the twig got me 0.35.

 

[GLENNSPARK]

My gas pipe is definitely straight in the ground, as I can see it - its an ancient iron/steel thing that disappears into the earth. Anyway, I disconnected the bond from the gas pipe and still got 0.46, but then it ocurred to me: as the pipe is connected to appliances which have their metalwork earthed, am I not getting a parallel path through their CPC's? I'm not going to the trouble of disconnecting those, or the bonds on the water pipe or central heating as they are under the floor and a pain in the arse to get to. I'm getting more confused about this by the minute!

The more I think about it I think it is the gas service, as (a) it is a metal pipe going straight into the ground, and (b) the gas-main in the road goes right past the transformer within about 2 metres of it.

Testing the MET without the twig got me 0.35.

stroppy...what is it exactly your trying to acheave here mate?
verify there either is..or isn`t an earth at the property?...if this is the case then you need to be discounting extranious paths....and you know how to be doing that...dont you...

 

[Stroppy]

hmm...well lets face it des...he should know that relying on extranious to bring down external loop isn`t on is it
we know this happens due to parallell paths but he should know the whole idea of doing a Ze in the first place...
if he cant fathom that one...then he`s no business testing ...has he...

I'm not relying on it, I and E54 are just curious as to how it manages to be so low, and yes I know about parallel paths and the purpose of Ze thank you.

As for can't fathom and no business testing, I presume you knew all about Zs Ze Ra parallel paths and testing as soon as you popped out of the womb, did you? No, you learnt it, which is what I'm doing.

 

[Stroppy]

What I'm trying to achieve is work out how my Ze is so low when E54 thinks it is impossible. It all started out of curiousity about my earth stake, which I knew would be rubbish so intend to upgrade it, unless I can get myself PME'd. And yes I've discounted the ext paths, leaving me with my 134 ohm earth stake as my 'official' earth path.

I suppose I've confused things by discussing this in a thread called "no earth." I should have started another thread "earth too good to be true!"

 

[Silly Sausage]

Stroppy, if you're that close to your local tranny, fit an MET in your house, then run a 16mm cable from it to said transformer and bolt your cable onto it. Cover it over with dead leaves and other general detritus.
Should give you the best Ze in the area.

 

[GLENNSPARK]

I'm not relying on it, I and E54 are just curious as to how it manages to be so low, and yes I know about parallel paths and the purpose of Ze thank you.

As for can't fathom and no business testing, I presume you knew all about Zs Ze Ra parallel paths and testing as soon as you popped out of the womb, did you? No, you learnt it, which is what I'm doing.

how did you guess?...the cable ends were a bit scratchy mind on the way out but...
well, thats what i was told anyway....