Jinx wrote: ↑Thu Oct 27, 2022 6:10 pm
Rod should be under 200ohms, or Code of Practice for Earthing recommmends sub 100. RCD/RCBOs should be used anyway, ideally a type B. I don’t understand the high voltage earth, what fault condition do you mean? The RCD simply measures current balance between Phase and Neutral.
The regs only require that the earth electrode resistance be low enough to pass sufficient earth fault current to trip the RCD, so the max value under any conditions is 1,667 ohms. The 200 ohms figure is only guidance, in the on site guide, and is set at that low a value to allow for the resistance increasing in dry weather. Obviously lower is generally better, but a supplementary rod electrode in parallel with the incoming PEN will never have a low enough resistance to prevent shock in the event of a PEN fault (even a 10 ohm electrode will exceed the safe touch voltage at only 5A of phase imbalance current trying to flow to earth - the phase imbalance current could easily be 100A or more under PEN fault conditions).
The fault condition where the incoming PEN is broken in the street (hence causing an apparent power failure) will cause the homes on the broken side of the PEN to have their earth conductors rise to a voltage above earth. This won't trip the RCD, as there is no current imbalance between line and neutral. The earth conductor could well reach a dangerous voltage under such a fault, well above the safe maximum touch voltage of 50V, due to the imbalance between phases in the street and the circulating return current going back down the lowest two phases, rather than the PEN.
This fault is normally mitigated by equipotential bonding, which ensures that all conductive parts inside the equipotential zone (i.e. indoors) are at the same potential. The fact that this potential may be a high voltage relative to the earth outdoors doesn't present a significant risk, as it's unlikely that anyone would be able to touch an "earthed" (i.e. equipotential bonded) part whilst they are standing outside and in contact with the local earth.
For this reason the earthing requirements for things that are outdoors and are not double insulated are more stringent than those indoors, and the incoming PEN cannot be relied upon to provide a safe earth for outdoor equipment, even with a supplementary local earth rod. The Type B RCD is a bit of a red herring, as that is only ever required where there is a risk of DC blinding. AFAIK, the only domestic equipment that requires a Type B RCD, or equivalent, is a car charger, because there is a very slight risk of pure DC leakage from the high voltage DC battery. Inverters normally need a Type A RCD (pulsed DC and AC capable) according to the regs, although there is a good argument that there could well be a DC leakage risk from a high voltage DC source, like solar panels (although the regs don't mandate a Type B for that application).
25 off 250W Perlight solar panels, installed 2014, with a 6kW PowerOne inverter, about 6,000kWh/year generated
6 off Pylontech US3000C batteries, with a Sofar ME3000SP inverter
, the other 2/5 electricians are absolute rip offs, charging like £500 for 1-2 hours work. So where is the line of getting things done properly. I carried on getting quotes until I got a decent price and someone who can sorta be trusted in 1 set of message exchanges, but for your average joe, he would probably have chosen one of the cheaper guys without asking the right questions. 
) 
Haha, no one ever told me that, just checked the RCD and Your right, it does say, in small writing! Only time it gets tested in my 10 years as a home owner is when it tripped swapping out some plug sockets. Or i guess whatever an electrician does when they are working on it.