Earth Tape As Opposed To Rod

[OnOff]

Figured here was the best place:

Soon to be putting in a new trench for a water main, 30m plus. Typically the trench will go through where the existing earth rod is. Currently in constantly damp ground at the bottom of an old water course anyway. From memory I measured 47 ohms which I think is good for TT but could it be better I wonder. Current, single rod is 3/8" dia, 4' long.

So I'm to dig trench and I got to thinking about running an earth tape in instead. I have no experience of earth tape use whatsoever. Worth thinking about or not? 

Cheers

 

[Manator]

I have never installed one myself but have been on site when they have been installed and watched with keen interest.

The tape I saw being installed was run like a ring around the building with earth rods pits at each corner for connections to the MET and the lightning conductor tapes.

You will probably get a very low RA as more copper is in contact with earth.

 

[Andy™]

never installed one either, but cant see any reason why it wouldnt work

 

[Sharpend]

As Manator really, seen pretty much the same. 

 

[Sidewinder]

Just do it, you will get near TN readings with a tape that length, especially if you chuck  a few 5/8" rods down every so far connected to the tape by reliable means.

Even 3 rods would help no end, one at the existing rod and one at least 2 rod lengths away either side, the more the merrier though.

Make sure you make a good connection tape to rod, the bigger the better, and non-insulated will help, as it is then in contact with the ground.

Denso paste or the like on the joints etc would help no end then wrapped in Denso tape.

If you are going to bolt, which is fine, to the earth tape then Denso everywhere, brass bolts would be fine.

Just Denso everything up.

An alternative to Denso is Bicon X1, in fact I prefer the Bicon.

This is a very common way of getting low RA readings, and is used by DNO's to get good readings at local TX's.

 

[OnOff]

The only thing similar I've even been close to is a mate in France who converted an animal shed into a "gite"  as he calls it. He had to employ a French sparks and the guy basically sunk a big copper plate in a dug hole where we would have whacked a rod(s) in. From the photos the thing looked 3'x3' at least.

Not saying I'll do it but is there any mileage in making my own "tape"? Thinking some lengths of 22mm copper pipe, flattened at the ends (or all the way along) joined by soldering and / or brass bolts etc. What's so special about the copper coating on normal rods?

This more out of interest tbh.

 

[Sidewinder]

I would check on the normal sizing for tape, I think that flattened 22mm copper pipe would be a bit small.

Also, you need to hard solder, or braze rather than soft solder for earthing, it's just the way it's done.

 

[misssweden]

Just do it, you will get near TN readings with a tape that length, especially if you chuck  a few 5/8" rods down every so far connected to the tape by reliable means.

Even 3 rods would help no end, one at the existing rod and one at least 2 rod lengths away either side, the more the merrier though.

Make sure you make a good connection tape to rod, the bigger the better, and non-insulated will help, as it is then in contact with the ground.

Denso paste or the like on the joints etc would help no end then wrapped in Denso tape.

If you are going to bolt, which is fine, to the earth tape then Denso everywhere, brass bolts would be fine.

Just Denso everything up.

An alternative to Denso is Bicon X1, in fact I prefer the Bicon.

This is a very common way of getting low RA readings, and is used by DNO's to get good readings at local TX's.

There is no such thing as too much denso  

 

[OnOff]

There is no such thing as too much denso  

Cheers. Yep, I was thinking Denso myself. I use it on high tensile bolts at work that are "black" but need protecting where zinc plating etc could risk hydrogen embrittlement. 

I did find out recently though that you mustn't use it on potable water pipes.

Can't see a flattened bit of 22mm pipe would be any worse than this:

https://www.edwardes.co.uk/en/products/kingsmill-ctba2530-25mm-x-3mm-bare-copper-earth-tape-per-mt?utm_medium=google_shopping&utm_source=google&utm_campaign=google_shopping

 

[Sidewinder]

Apart from pipe is semi-hard, or hard drawn, and tape is annealed and soft.

The resistivity of copper increases with the mechanical hardness.

Therefore your hard drawn copper pipe would have a higher resistance than the tape to start, then you would be cold working it to flatten it and increasing the resistance again.

The next thing is that earth tape is designed to conduct electricity, 22mm copper water pipe is designed to conduct water, a slight difference!

You will find that the resistivity of copper water pipe is significantly higher than earth tape in a "virgin" state.

Also,what is the wall thickness of 22mm copper tube, much <1.5mm I suspect.

Check BS 7430 out as a starting point.

You can do this and do it well, and just because you have a TT does not mean you must have RCD's, IF your TT earth is reliable...

30m of earth tape, and 3 or more rods is pretty reliable!

 

[kerching]

Back in the day we used to,do,BFO server rooms/farms

usually a 11kV sub outside giving us 1600 A/phase

DNO used to strip a length of 25mm Earth wire, run it around outside of Xformer base concrete and connect it to  5/8th rod at each corner ( think,it was 25 mm might have been bigger)

 

[misssweden]

It's 70mm these days kerch  

 

[OnOff]

Over a tenner a metre for that 25x3 stuff! Think I need to find a friendly lightning protection man to sleep with!  :tongue in cheek

 

[Sidewinder]

Shop around, there are other places to get it from.

Normal online wholesalers are not the place.

However, it will not be cheap to do it right, it never is.

 

[kerching]

I Wonder if it may have been some 70 mm then?

I was expecting something a bit more sophisticated than just stripping a bit of earth wire!

mind you....then ran a spare set of MVs out from the Xformer and just folded some braided tape over the cut ends, nailed it on with some plasterboard nails and shrunk a cap on the ends

just interesting

 

[binky]

Changing tack slightly, what is the life-span of buried copper?

 

[misssweden]

I Wonder if it may have been some 70 mm then?

I was expecting something a bit more sophisticated than just stripping a bit of earth wire!

mind you....then ran a spare set of MVs out from the Xformer and just folded some braided tape over the cut ends, nailed it on with some plasterboard nails and shrunk a cap on the ends

just interesting

Was it not bare 70mm then?

 

[Sidewinder]

Changing tack slightly, what is the life-span of buried copper?

A blinking long time.

My 15mm incoming water pipe to my house has been buried for over 50 years and it wasn't leaking the last time Welsh Water came around to check a few weeks ago.

 

[binky]

How old was the Saxon hoard :^O

I suppose it varies with soil conditions, but it's one of those things that crosses my mind occasionally that I have never seen any guidance on.

 

[roys]

Round our 11 kV switch rooms we had (from a fading memory) a bare 120mm2 cable buried with a bare 70mm2 T'eed of it at regular intervals to an earth rod.  To T of the 70mm2 from the 120mm2 we CAD welded it which is a great job.

Just speak to Steps I am sure he has ran some big lumps of copper through his mangle recently.  Like the idea of putting in a good earth while you have a trench dug.

on a totally separate note don't think the copper pipe is going to last too long in my house, my water is supplied from my own well, it has a ph of 5.  When ever a tap drips it leaves a blue stain and if my wife washes her hair it turns it a nice bluey green colour due to copper leaching from the pipe work and cylinder.