Maybe use copper Earth tape?

[timhoward]

I'm installing a new supply to a ceremoniously dumped welfare cabin. I can't see any legitimate reason not to apply section 717, welfare units are specifically mentioned and the thing is a mobile/transportable unit. In turn this dictates that it shouldn't be connected to a TN earth as to my thinking at least none of the exceptions apply. Any arguments countering this are welcome!
So my current plan is TN up to a box near it, then become TT.

My question is about possibly using earth tape (I've never used it). As there's a nice 2.5ft deep 10ft long trench in preparation for a drain I thought it might make sense to use earth tape instead of banging rod(s) in.
I believe that I've calculated that 3m of tape, 0.75m down, with soil resistivity at an arbitrary worst case 150ohm-meters should give me 35 ohms impedance. As I can see clay I think this is a reasonable worst case guess.
Any superior wisdom welcomed, I'm really seeking confirmation that it's likely I can get a better result far more easily with tape in this case.

 

[UNG]

No reason why you can't, you could always add a rod or 2 at each end of the trench connected to the tape

 

[pc1966]

Earth tape is a good idea, even adequate size of bare copper wire would be good and might be easier to bring out and/or crimp join to an insulated./sheathed conductor to the cabin. A trench 2.5 feet down ought to avoid frosting and any major risk of drying out.

 

[Lister1987]

Consider condu-disc and condu-crete.

ConduDisc - Earthing Services

Earthing without rods: ConduDisc is changing the way earthing / grounding systems are installed. Easy to use, fast to install, highly effective.

earthingservices.com

Conducrete - Earthing Services

Conducrete is independently proven to be the best earthing / grounding product of its kind in both laboratory and field tests. Relied upon by the best.

earthingservices.com

 

[timhoward]

Consider condu-disc and condu-crete.

Thanks .....but I already have!
In this case I'm not sure it's the obvious choice as there is already a nice big long deep trench. The internet is silent about the actual cost of them, and anything you have to ask the price of is usually liable to require a stiff drink afterwards to recover.

 

[timhoward]

Thanks all

Earth tape is a good idea, even adequate size of bare copper wire would be good

Thanks for the idea. The earth tape I was looking at was 25 x 3mm. Result should have in fact been 45 ohms. (area vs diameter mistake!)
If I bung in 16 sq mm bare copper that gives 47 ohms, and that is worst case for soil conditions. If I add a rod for good measure I think this idea should be fine.
I'll report back on the final impedance result!

 

[UNG]

Thanks .....but I already have!
In this case I'm not sure it's the obvious choice as there is already a nice big long deep trench. The internet is silent about the actual cost of them, and anything you have to ask the price of is usually liable to require a stiff drink afterwards to recover.

It is quite surprising how you can never find the price for some these pieces of kit and that also casts doubt on the availability

 

[pc1966]

It is quite surprising how you can never find the price for some these pieces of kit and that also casts doubt on the availability

I am always suspicious of products that are not quoted (unless obvious issue like custom build) as experience has taught me it means "stupidly expensive, but now we will pester you with sales calls".

 

[Robson689]

It is quite surprising how you can never find the price for some these pieces of kit and that also casts doubt on the availability

I don't even see the benefit of them vs a £40 300mm²/600mm² earth mat

 

[UNG]

I don't even see the benefit of them vs a £40 300mm²/600mm² earth mat

Neither do I but when someone brings something to market it is always of interest to know what price point it is at for comparison purposes

 

[freddo]

The Conducrete looks useful, but it appears to be extremely difficult to get hold of. Why is this product not readily available at electrical wholesalers?

 

[Robson689]

The Conducrete looks useful, but it appears to be extremely difficult to get hold of. Why is this product not readily available at electrical wholesalers?

I could be wrong but it sounds and looks exactly like marconite which can also be bought premixed with cement.