3 Lead RCD Test in the Consumer Unit on RCBO's Saving Time During the Live Testing's Process Student training aid for testing an RCBO rated at 30mA using a MFT Megger tester. Includes a full demonstration of how to test the RCBO using 3 leads from with the consumers unit. Note my default position is always 3 lead testing as it’s my preferred method of testing for Earth Fault Loop impedance when RCD protection is present. 2 lead tests can also be carried out for both testing RCDs and circuit Impe