BG RCD is suitable for circuit protection. The two module, double pole RCD provides earth fault current protection for residential and light commercial applications. It is the common Type AC, suitable for situations where there are residual sinusoidal alternating currents. The Time Delayed RCD is used typically when two RCDs are installed in series and the time delayed RCD enables discrimination, that is in the event of a fault only the ‘upstream’ RCD should trip. It has a positive contact status indicator, that is when green window is visible this indicates that there is a 4mm contact gap.