The Value of R.C.D.s

By taste I like everything in a home, from soon after the meter, to have ≤ 30 mA RCD protection.  Apart from giving some backup for direct contact or broken earthing, and sometimes faster disconnection than OCPDs, it avoids the potential for lethal currents to leak to building structures, etc - there's the well known case in the UK, and a more extreme example here (Australia, double death, showers, concrete floor, nail: link).  For my own systems I just feel it unnecessary and unacceptable to avoid this simple addition. 

Doubtless some lives have been saved by RCDs, though probably a good deal fewer than we might think from looking at the correlation of higher RCD coverage and lower death rate over time.  I suspect that product standards have played a big role, e.g. avoiding grippable conductive parts.  Plenty of shocks happen unreported that don't cause death even without RCDs, so the cases of “I got a shock and it tripped - the RCD saved me” wouldn't necessarily have been fatal.  I wouldn't be surprised if there's been as much positive effect from RCDs on fire deaths as on shock deaths, particularly in systems with earths around or between live conductors; but those statistics are even more shaky. 

In Sweden RCDs were uncommon up to the 1990s or so, and I see many houses without them, often with old installations, outdoors extension leads, cars etc. (In contrast to the recent worries about car chargers in the UK, it's been thoroughly normal for decades to have cars's chassis earthed by their class-I engine-block heaters, and plenty of cars still do so in old installations with no RCD; besides this, they practically all lead back to a ‘PEN’, often within the customer installation in the older ones before the harmonized rules around the 1990s put a big minimum size on such conductors). In spite of all this, there have been years with no electric shock deaths at all (nationally, any cause) and the few that usually happen in a year tend currently to be electricians or line workers at work, or youths clambering on parked electric trains unaware of the 15 kV 16.7 Hz hazard in the wires on and above the train.  So although I sometimes subtly stick RCD plugs onto extension leads that I see branching to dozens of outdoors power tools, cement mixer, etc, I have to admit the statistics don't really justify a great need compared to other risks we accept.  My own tastes are based on its being such a simple addition “just in case". 

By taste I like everything in a home, from soon after the meter, to have ≤ 30 mA RCD protection.  Apart from giving some backup for direct contact or broken earthing, and sometimes faster disconnection than OCPDs, it avoids the potential for lethal currents to leak to building structures, etc - there's the well known case in the UK, and a more extreme example here (Australia, double death, showers, concrete floor, nail: link).  For my own systems I just feel it unnecessary and unacceptable to avoid this simple addition. 

Doubtless some lives have been saved by RCDs, though probably a good deal fewer than we might think from looking at the correlation of higher RCD coverage and lower death rate over time.  I suspect that product standards have played a big role, e.g. avoiding grippable conductive parts.  Plenty of shocks happen unreported that don't cause death even without RCDs, so the cases of “I got a shock and it tripped - the RCD saved me” wouldn't necessarily have been fatal.  I wouldn't be surprised if there's been as much positive effect from RCDs on fire deaths as on shock deaths, particularly in systems with earths around or between live conductors; but those statistics are even more shaky. 

In Sweden RCDs were uncommon up to the 1990s or so, and I see many houses without them, often with old installations, outdoors extension leads, cars etc. (In contrast to the recent worries about car chargers in the UK, it's been thoroughly normal for decades to have cars's chassis earthed by their class-I engine-block heaters, and plenty of cars still do so in old installations with no RCD; besides this, they practically all lead back to a ‘PEN’, often within the customer installation in the older ones before the harmonized rules around the 1990s put a big minimum size on such conductors). In spite of all this, there have been years with no electric shock deaths at all (nationally, any cause) and the few that usually happen in a year tend currently to be electricians or line workers at work, or youths clambering on parked electric trains unaware of the 15 kV 16.7 Hz hazard in the wires on and above the train.  So although I sometimes subtly stick RCD plugs onto extension leads that I see branching to dozens of outdoors power tools, cement mixer, etc, I have to admit the statistics don't really justify a great need compared to other risks we accept.  My own tastes are based on its being such a simple addition “just in case".