Earth detection

[howie]

Problem: I can see an earth cable running from the consumer unit which could be running to the earth rod, however, I cannot find the earth rod.

Without pulling the ceiling down and investigating it's path, is there another way of detecting the earth block in CU has a connection to ground (i.e using a meter reading..)?

Any ideas??

 

[andy]

take a floorboard up and stick your head under. look to see if you can see an earthrod. look around the outside of your house for an earth wire coming out and going underground

 

[SparkyTris]

I'm not an electrician, but I might do the following to check an earth connection:
construct a known earth rod by driving a few heavy copper spikes into damp ground nearby & linking them with heavy cable. Then check the resistance between this contrivance and your 'suspected earth' using a high-impedance ohmmeter. A resistance of below 20 Ohms would indicate that the suspected earth is actually connected to ground. I'm not sure whether this is a good method (it's certainly quite involved) or even whether it would work. Could be a load of hogwash. But I think it's a good question.

Most probably, though, the earth wire you see is either connected to an earth conductor on the incoming header (a TNS supply), or it's bonded to the neutral on the incoming header (TNCS supply).

professionals - is any of what I advise correct?!

 

[howie]

take a floorboard up and stick your head under. look to see if you can see an earthrod. look around the outside of your house for an earth wire coming out and going underground

Thanks for replies

Unfortunately I cannot take floor boards up as there is t+g flooring upstairs and would involve taking up a rooms worth of timber!

There is no earth cable on the outside of the building, although there a porch has been added and am wondering if the earth rod has been buried during construction.

I'm wondering if there is a non -invasive method of wether there is a good earth connection to ground?

 

[andy]

take a floorboard up and stick your head under. look to see if you can see an earthrod. look around the outside of your house for an earth wire coming out and going underground

Thanks for replies

Unfortunately I cannot take floor boards up as there is t+g flooring upstairs and would involve taking up a rooms worth of timber!

There is no earth cable on the outside of the building, although there a porch has been added and am wondering if the earth rod has been buried during construction.

I'm wondering if there is a non -invasive method of wether there is a good earth connection to ground?

try sparkytris' idea. its a long way to test it, but it should work

 

[SparkyTris]

Try just sticking one probe of your meter in the ground (via a nice thick cable if your test-leads aren't long enough.), and stick the other probe on your "suspected earth". Measure resistance. If it's below 20 ohms, your suspected earth cable is indeed connected to earth. Probably.
what sort of meter do you have?

 

[howie]

Try just sticking one probe of your meter in the ground (via a nice thick cable if your test-leads aren't long enough.), and stick the other probe on your "suspected earth". Measure resistance. If it's below 20 ohms, your suspected earth cable is indeed connected to earth. Probably.
what sort of meter do you have?

thanks, I have a cheap meter (Clarke). I'll give it a try.

 

[Lectrician]

Do you have an RCD for this installation - I hope so.

A loop impedance tester would be best.

If you test by this method, or those stated above, ensure you test to the cable to the 'rod' only, and not to the whole earth block. You could measure parallel paths etc (possibly galv gas pipes, lead water pipes between you and a neighbour on PME/TNS.

If you have PME or TNS, you can tell by looking at the meter and service fuse. Is there an earth cable terminating at the meter kit?.

 

[ban-all-sheds]

Problem: I can see an earth cable running from the consumer unit which could be running to the earth rod, however, I cannot find the earth rod.

Without pulling the ceiling down and investigating it's path, is there another way of detecting the earth block in CU has a connection to ground (i.e using a meter reading..)?

Any ideas??

take a floorboard up and stick your head under. look to see if you can see an earthrod. look around the outside of your house for an earth wire coming out and going underground

Thanks for replies

Unfortunately I cannot take floor boards up as there is t+g flooring upstairs and would involve taking up a rooms worth of timber!

Howie - does this cable from the CU head off in a groundwards direction, or does it go up into the ceiling?

 

[howie]

The cable definately runs into the ceiling and doesn't terminate at the fusehead.

Thankfully I am protected by an RCD CU, but not knowing if I have a reliable earth is a bit worrying!

 

[plugwash]

to be totally honest its probablly easier/better to just fit a new rod or get a PME conversion done

even if your meter tells you a wire is connected to earth it can't tell you if it is connected by acceptable means.

 

[howie]

to be totally honest its probablly easier/better to just fit a new rod or get a PME conversion done

even if your meter tells you a wire is connected to earth it can't tell you if it is connected by acceptable means.

I think you're right, not being able to see an earth rod and it's connection is not very reassuring.

Is installing a new earth to rod circuit within the capabilities of a competent diy'er (i.e. are there any tests required post installation)? If so would you use 16mm or 10mm earth cable to run it?

 

[ban-all-sheds]

Is installing a new earth to rod circuit within the capabilities of a competent diy'er

It's never struck me as difficult to bang a rod into the ground, but there may well be skill needed to avoid bending it, and experience needed to pick the right place. It probably doesn't take long to do, so you might as well get an electrician to do it because
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(i.e. are there any tests required post installation)?

And there's the problem - yes, there are, and I doubt you've got the necessary test gear.

If so would you use 16mm or 10mm earth cable to run it?

Depends on whether it's buried, protected against corrosion, mechanical damage etc. See Table 10C in the OSG, and if you don't have a copy of that, get one immediately - it's essential.

What's the rest of your installation like? Do you have any main or supplementary bonding?

 

[howie]

Thnaks for all the replies guys....

See Table 10C in the OSG, and if you don't have a copy of that, get one immediately - it's essential.

Sorry for the ignorance, but what is and where can I get the OSG?

What's the rest of your installation like? Do you have any main or supplementary bonding?

That's another problem - there is no bonding, except under the new boiler where all pipes beneath have been cross bonded.

My plan is to bond the gas and mains water back to the CU and run a new earth circuit to a new earth rod. I'm not sure what size cable to use, I have an excess of 6mm which I know I can't use for the rod connection but is this cable of sufficient size for the bonding of the mains water and gas?

 

[Careful_Bodger]

OSG? = On-Site Guide see the Reference section (page 2; posted by B-A-S), where you will find, among others

http://www.amazon.co.uk/exec/obidos/ASIN/0863413749

...though I have to say that although the OSG states the (rather puny in certain cases) CSA for TT supply earthing conductor sizes, I was happier to DIY install the higher rated 16mm2 and 10mm2 - for various reasons, including 'cos it seemed more robust, allows a possible future 'upgrade' to TN-C-S, and 'cos I felt better about it.

Figure 4c might also be useful.

On another note - I have heard that getting an earth spike in can be made much easier by fitting a garden hose to a appropriate length of rigid pipe, and using the flow of water as a kind of water powered drill. Any thoughts on this particular ?