Difference between ELCB and RCCB (RCD)

I suppose this is where my age and the age of the ELCB (earth leakage circuit breaker) comes in.

In the 60's ELCB's came in two guises, current operated and voltage operated.

The current operated working on core balance became the RCCB (RCD) that we know today.

Voltage operated relied on there being only one earth path from an installation for it to work effectively.

So for example your house would need to have plastic gas and water mains so that there was no parallel earth paths. The only earth path would be via the main earth bonding wire through the ELCB's voltage coil out to an earth spike.

Now think of the problems;

You run a copper pipe to a tap in your garden. You build a metal-framed garage and install power. There were 100's of ways of creating parallel earth paths all of which made the ELCB inoperative. Another failing was under heavy fault conditions the voltage coils internal resistance caused the installations potential in relation to earth to rise, also under heavy fault the coil could burn out (I'll leave you to figure out what the result is).

Voltage operated are now illegal.

The term RCD was introduced to differentiate between the two types