Chint 40A 30mA RCD
RCDs (Residual Current Device) sometimes called RCCBs
RCDs monitor neutral and earth for an imbalance which would normally indicate a leakage to earth. Once this exceeds a pre-determined amount the RCD will trip. It is important to note that they are designed to operate within a percentage amount of the RCDs maximum sensitivity and not run right up to the maximum sensitivity shown on the RCD.