Testing 101: Earth Fault-Loop Impedance and Residual Current Devices

Since the release of the updated Wiring Rules, ECA WA Technical have received a number of queries regarding testing requirements for Earth Fault-Loop Impedance (EFLI) and Residual Current Devices (RCDs). Members are advised to review the following points which clarify the key features and requirements: 

Earth Fault-Loop Impedance testing (AS/NZS 3000:2018, clause 8.3.9)

  1. EFLI testing is only required on circuits where all of the conditions below are met: (a) Fault protection is by automatic disconnection of supply (b) The circuit supplies one or more socket outlets (c) The socket outlets are not protected by a 30mA RCD or less. 
  2. EFLI testing is not required for RCD protected socket outlets due to the maximum operating time being less than 0.4 seconds (5.7.2).
  3. EFLI testing is not required for circuits supplying equipment other than socket outlets due to the longer permitted operating time (5 seconds) combined with the verification of earth continuity being considered adequate to comply with clause 5.7.2 (disconnection times).
  4. Whilst ELFI testing is not required for other circuits, the maximum permitted trip times must be obtained. This is complied with if circuit volt drop requirements are met.
  5. In essence, the only circuits requiring ELFI testing are socket outlets which are rated at > 32 amps as they are not necessarily RCD protected.

Residual Current Device testing (AS/NZS 3000:2018, clause 8.3.10)

1. RCD’s shall be tested to verify they have been correctly installed.
2. The function of the RCD shall be tested by either operation of the test device or by special test equipment.
3. Correct isolation of all poles shall be checked by voltage or continuity tests.
4. In Australia, testing is not required if supply is not available.
5. There is no mandatory requirement to test the operating time of the RCD.

Please contact ECA WA Technical on technical@ecawa.org.au or phone 1300 6322 8324 if you have any further queries.