Puzzled about use of Earth Rod Terminal Box

[jkn]

Hello all I have a TT earth system supplying mains power to my Garage. The earth (6mm cable IIRC) runs from the garage CU to an earth rod situated nearby.

Whilst at TLC recently I picked up an 'earth rod terminal cover' in an attempt to tidy up the clamping arrangement to the earth rod:

However this unit turns out to be not quite what I expected and I'm a little unclear how it's supposed to be used.

The earth rod clearly goes in the bottom tube (which swivels), and then there is just a 20mm or so hole in the side of the box. Is this intended to take a cable gland for the earth cable? Or just a grommet of the appropriate size? And why the swivel? I'd have thought this would encourage small children to play with it and maybe loosen the internal clamp arrangement.

Thanks for your thoughts

J^n

[Pete Verdon]

I think you've got it backwards. I fitted mine the way up it is shown in the picture, with the rod exiting through the open hole in the bottom and a conduit for the cable fitted onto the "tube". I can't remember exactly how the conduit attached, it's been a couple of years, but are you sure your "swivel" isn't a screw thread for screw-in conduit fittings?

My box is then sunk slightly into the ground so that just the top, with the warning label, sticks out a little.

Pete

[cynic]

The entry shown on the right is a conduit connector which you would use to fit a length of conduit into and bring the green/yellow earth wire through from the clamp to safely end up above the surface of the ground on the run up the wall to the MET position. The rod would be driven into the ground through the bottom of the box. Ideally the insulated box will be flush with the ground surface to minimise surface potential gradients in the event of fault current passing through the earth conductor into the ground. This particular box looks a bit on the small (shallow) side but its better than nothing I suppose. I suggest you get your hands on a copy of the CITB book on BS7671 2008 in which technical data sheet 5B/4 is very explanatory. Your local reference library may be able to help if you dont want to buy the book. (ISBN 978-1-85751-278-6)

Can I suggest you

[Rob G]

Based on your comment about this particular box being rather too shallow in your experience, can you suggest a supplier of one that you would use. I'm about to fit an earth rod in a similar situation to the OP.

Thanks Rob

[ARWadsworth]

The entry shown on the right is a conduit connector which you would use to fit a length of conduit into and bring the green/yellow earth wire through from the clamp to safely end up above the surface of the ground on the run up the wall to the MET position. The rod would be driven into the ground through the bottom of the box. Ideally the insulated box will be flush with the ground surface to minimise surface potential gradients in the event of fault current passing through the earth conductor into the ground. This particular box looks a bit on the small (shallow) side but its better than nothing I suppose.

The conduit entry may be swapped for

but it looks more like a surface mount rod cover than a sunken one.

Adam

[js.b1]

There are larger pits like the following...

- Screwfix

- Plastic Inspection Earth Pit - 16092

-

?ts=63381#It is a bit more, probably too, industrial.

[BigWallop]

Based on your comment about this particular box being rather too shallow in your experience, can you suggest a supplier of one that you would use. I'm about to fit an earth rod in a similar situation to the OP.

Thanks Rob

Try here

for a good supplier.

[jkn]

Hi Chaps Thanks for all the comments and suggestions.

One followup - my current earth rod, composed of two 4foot (I think) Furse rods screwed together, sticks out of the ground a couple of feet

- I can't hammer it in any further. Would it be acceptable to cut this down nearer to the ground? They are probably the copperbonded steel cored type.

Thanks J^n

[BigWallop]

Put a fancy flower pot in front of it, just to stop people falling over it. :-) lol

Try cutting the very tip off, to see material it is, and then cut it down to suit the level you need. If you're using a proper clamp, it won't matter where that is sited on the rod to do its job.

[tony sayer]

If its a proper Furse it'll be high tensile steel!..

Cut it and make sure its got a good dollop of sealant on it, should be fine:)..