First TT installation

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As per title I will be doing my first rod install in the near future.

I'm looking for recommendations as to what kit people prefer - rod sizes , brands, inspection pits etc and general tips and methods/advise regarding the installation itself.

All help much appreciated. Many thanks.

 
depends on your area & ground conditions. around here you can easily get <50 ohms on a single metre rod even partially in. other areas need multiple extendale rods to get any reasonable reading

 
CAT scan to find any buried services.

SDS Max set to hammer only with a rod driver.

5/8 rods, surface area is the key.

Place the rod a good distance away from any foundations to avoid rubble and cavities that will give you poor readings.

If you need to add a second rod location make sure it's placed 3x the distance away then the depth of the existing rod to avoid encroaching on the rods sphere of influence. For example if you have 1m depth go 3m away, 3m depth go 9m away.

In very poor ground conditions consider using tape in a trench, conductive concrete etc to get more stable results.

 
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It would help to know what type of building it is.

If it’s a new build @Sidney‘s suggestion of a copper tape makes life easier as it can go alongside drains. It’s the method I used for my first house, finding 600ft of redundant gas pipe made it even better.

 
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It would help to know what type of building it is.

If it’s a new build @Sidney‘s suggestion of a copper tape makes life easier as it can go alongside drains. It’s the method I used for my first house, finding 600ft of redundant gas pipe made it even better.


Its an existing farm labourer's semi detached cottage - probably 60/70 years old .

No obvious sign of any existing rod - I suspect earth is currently via water service (about 56 ohms) - but I haven't been able to get in and have a proper root around yet...

 
You can't really quote for a TT system  because of the type ground .   Last one I did ended up with 6   X 2m  rods .

Because I know my wholesalers  over the last 30 yrs  I  now  take  at least four rods  plus a few couplers etc .  to save dashing off for more . 

 
Initially make sure there is definitely not an earth rod present as it can be tedious installing a new earth rod, depending on ground conditions.

Sidney has given a lot of useful information.

The most cost effective method for small installations is using a copper clad steel extendable earth rod, or two, or three or more!

You are looking to get the lowest resistance you can with the most practicable installation, very variable around the country and even if the geology is different next door!

5/8" earth rods are the most commonly available sensible choice, the 1/4" rods bend easily and are not connectable to give more depth, thicker rods or all copper rods are not going to make a significant difference to the resistance on a small installation.

If the insertion of the rods is easy then going deeper with longer coupled rods is generally more stable than having multiple earth rods only 1200mm deep, though if you only have a thin layer of earth you do not want to be trying to hammer through rock.  If the ground is really bad you can drill with a long SDS drill bit first but make sure the hole is smaller than the earth rod so you get a better contact with the ground, best avoided if possible.

You will need a means of being able to hammer, either with an SDS drill on roto stop or by the good old sledge hammer, the earth rod in without splaying out the end.

I tend to use a coupler on top of the rod with a 5/8UNC bolt in the coupler, but the coupler does take some strain. For the SDS I have a socket for the bolt welded to an SDS end.

Different earth rod clamps are available, you will probably get the best connection with a lug connection to a bolt, but I often use the clamps that allow the cable to be clamped with the rod (the screw being always against the rod not the cable) as it is quicker.  But if you are using a thin earth cable it may not hold.

Ideally you want an decent earth pit to protect the connection and yet still make it accessible for testing.  Unless there is traffic driving over it a plastic one should be fine but if there is then a concrete one.  If you are saving costs then the small plastic boxes can be used, the little round ones look a bit rubbish.  The earth rod should be labelled with "safety electrical connection, do not remove" (for some reason, regulations or something!).

Remember that the current taken will be low so a relatively small diameter (not less than 2.5mm²) cable can be used, but it is often easiest to use the 10mm² you have in stock, 16mm² if buried.

Earth rod.jpg

 

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