RCD _ residual current device, essentially a GFI but usually entirely electro-mechanical rather than electronic. Trip currents range from 10 mA to 3 A for ancient models, currently up to 500 mA I think. For all outlet circuits 30 mA are required in most countries these days, requirements for lighting circuits and fixed appliances vary. Earthing arrangements play a role as well, in a TN-C-S system similar to US practices it is sometimes allowed to have circuits without RCDs, in a TT system (only a local earth rod, no connection to the neutral) RCDs are usually necessary for all circuits as the fault current will not be high enough for a fuse or MCB.
MCB = miniature circuit breaker, plain old breaker in US terms.
Edit: RCBO = combined RCD and MCB, i.e. GFI breaker.
Last edited by Texas_Ranger; 09/17/14 08:54 AM.
