Wiring of the Distribution Board with RCD (Single Phase Wiring of the Distribution Board with RCD (Single Phase Home Supply) Wiring of the Distribution Board with RCD , Single Phase, (from Energy Meter to the main Distribution Board) Fuse Board Connection. Main Distribution Board or Fuse Boards ( Consumer Unit) usually contains three main units. They are as follow: RCD (Also DP) Residual Current Devices.[PDF] ISSUE 40 - November 2003 CONFUSED RCCBs usually have a fault making and breaking capacity in the order of 1 kA. This means that they can handle a fault of 1 kA on their own if it is a fault to earth. For overloads and line to neutral short circuits, the Wiring Rules require other devices to provide protection.