TT earthing system second rod

[Sidney]

Hi all, I would like to put a second earthing rod at a garage that is a little remote from the house, so as well a using the house earthing the garage would have the second rod, this would also add a second earthing route for the house, Is this permissible and can anyone see any problems occurring . Sidey

 

[Richard Burns]

I can't see a problem, so long as they are connected above ground through the installation then you will have lowered your Ra which can only be a good thing.

 

[Sidney]

Hi Richard, Thanks for your reply, I had done the relevant impedance calculations and could see no problems but needed a second view in case I had forgotten something. If you have already had this reply it's because I'm just getting to grips with this site. Sidney

 

[davesparks]

In principle it sounds fine to me subject to a few considerations.
1 the earth conductor connecting this second rod back the the main installations MET should be at least 6mm copper if my memory is correct and assuming it is not buried and is protected from mechanical damage etc etc.
2 the new earth rod should ideally be spaced from the existing rod by a horizontal distance equal to or greater than the sum of the lengths of both the existing and new rod.
The reason for this is that rods placed too close together will have overlapping spheres of influence, so under fault conditions will not achieve their best possible resist ace to earth.
But how on earth you will know the length of the existing rod I don't know! Even if the details of the original rod are recorded in the paperwork it will probably have been lost or eaten by the dog.
Apologies if this is teaching you to suck eggs, but it may be helpful to someone else reading the thread.




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