E
Engineer54
Think you'll find that the formula is based on the buried depth (length) of a given rod or coupled rods!!
I have no idea where you get the 2.2 X L as being the standard distance for general soil conditions ...it's certainly not a figure that i've seen before!!!! lol!!
The only time you would think about going to 2X or more, would be in the most favourable soil conditions where the zone of influence of a given rod would/could be enhanced, or between separately derived earthing systems. If your talking about an earth ring around a building, yes it would be prudent to go with greater distances between earth electrodes (rods), but this is mainly to cut down on overall costs, rather than for over lapping purposes/measures. Same goes for lightning protection systems where it's not unusual to see 10 metres between 3m earth electrodes (rods).
I'm used to using 3m x 3/4'' copper bonded rods, and generally in ground field installations. I have never had a distance between the rods that exceeded 5m and can assure you that we have never seen any instances during testing of the individual rods (or between grids) of overlapping zones of influence, ...not One!! Were talking here in the 10's of 10's rods, making up these ground fields and being set out in integrating grids....
So i'll Stick with what i have previously stated and what i know, that 1.5X the buried depth (length) of the rod is ample for general soil conditions... I'm not saying there is anything wrong with greater distances between rods, ..just that they would generally serve no useful purpose...
