Earth leakage circuit breaker
- The term Earth leakage circuit breaker (ELCB) is often incorrectly used to describe its modern counterpart the Residual current device (RCD).
An earth leakage circuit breaker (ELCB) is a device with two earth terminals used to directly detect currents leaking to earth from an installation and cut the power. They were mainly used on TT earthing systems before RCDs became common. They have been almost totally replaced by RCDs (except in very old installations) due to a number of problems.
- They cannot detect earth faults that do not go through the earthing system.
- They do not allow a system to be easily split into multiple sections with independent fault protection, due to the fact that earthing systems are usually bonded to things like pipework.
- They may be tripped by external voltages on something connected to the earthing system such as metal pipes, a TN-S earth or a TN-C-S combined neutral and earth.
- They introduce additional resistance and an additional point of failure into the earthing system.