guys all this talk of soaking, urinating on, or waiting for the rain on rods is missing the point.
suppose you do relieve yourself over the rod and get below the made up figure of 200ohms, then woopdedoo.
Presumably the couple will give you a ring when they think there is a fault about to occur?
or maybe you could put an entry on the certs "customer to use own bodily fluids to reduce fault path on a regular basis"
it is the STABLE reading that you want, not an artificially low reading that you have created!
regarding the 1667 ohms, it is irrelevent whether or not you are using a spike or / and on a TT system. if 1667ohms or less is achieved the 30mA RCD is going to trip in the requireed time and before the touch voltage reaches 50V
Rich, TT's are not a problem. If you are concerned about the reading and want to sort it, go in deeper with the rod. We used to use rods with a threaded end, then put in an line copper ferrule on it and keep driving in. Alternatively you add additional spikes, and connect together. If you were using four spikes the accepted method is to connect them in a 'box' formation, this gives a better overall resistance reduction.
Just be aware, that the reduction is on a non linear scale, both for deeper rods and/or additional rods.
i.e. if a rod was 300 ohms for example, driving it in twice as deep, or providing a second rod would not half it to 150, you are more likely to get about 230 - 240 ohms.
and when i said 'made up' figure of 200 ohms, it is becasue the reading is just a 'supposed figure'. below 200 is likely to be more stable than above 200. but lets say it was 200 in the winter (when the readings are lower) and in the summer it was 400, as long as it stays below your 1667 ohms (presuming 30mA used) then you will still be ok.
even with a 100mA RCD you have 500 ohms to play with!
and remember the 1667 ohms is only to achieve 50V touch voltage, the 30mA RCD will still trip at values of up to 7667 ohms
