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Onoff

Earth Tape As Opposed To Rod

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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

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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.

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Andy™

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

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Sharpend

As Manator really, seen pretty much the same. 

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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.

 

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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.

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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.

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misssweden
32 minutes ago, Sidewinder said:

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 :D 

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Onoff
9 minutes ago, misssweden said:

 

There is no such thing as too much denso :D 

 

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

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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! ;)

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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)

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misssweden

It's 70mm these days kerch :) 

Edited by misssweden
Brainfart :D

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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

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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.

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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

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binky

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

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misssweden
33 minutes ago, kerching said:

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?

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Sidewinder
4 minutes ago, binky said:

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.

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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.

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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.

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Sharpend

Is that where the blue rinse comes from? 

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Tony S

A peripheral earth as the septics call it.

 

I’ve used 1x⅛” copper tape laid along side the drains. As SW said if you need to join it use “tinmans” hard solder. The icing on the cake was finding a disused gas main. I welded a stud to the pipe and ran some tape to it. On the joints I used hessian tape and then poured cable compound over it.

 

At work we used a buried copper mat at some of the remote subs. Most subs used the plant steelwork. Newer subs also used the foundation rebar as an Ufer earth.

 

Note,

How to annoy the wife, ruin one of her pans melting Trinidite compound.

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Onoff

I've had to give up gently warming half tins of Temaxol on the hob so the swarf sinks to the bottom. I like the smell but apparently "it's a kitchen NOT a workshop! "

Edited by Onoff

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Onoff

So out of the blue I've been given a roll of 9mm x 1mm busbar strip. So 9mm2. Length is "umpteen" metres :)

 

Not sure whether to whack in the as yet to be backfilled water main trench and attach to my existing rod or just weigh it in! I won't be testing it until I backfill. (Still got the CCTV duct to lay too).

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binky
On 7/25/2016 at 20:54, Sidewinder said:

 

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! ;)

 

So ho would you define 'reliable'? I think the lowest rod resitance I've seen was about 2 Ohms on  a wet  winters day and TN-C-S allows 0.8 Ohms max. The possibility of dispensing with 100mA Type S rcd protecting tails to a metal board filled with RCBOs is rather appealing to me, it seems daft to RCBO everything then have a single RCD, the whole point of using RCBOs being to avoid sharing an RCD.

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