Test 2 – Resistance of the earth continuity conductor.
Written by: Grant Seeman – ECA(SA) National Technical Advisor
A practical series on the four inspection questions and 15 tests in SANS 10142-1
The second test in Section 4 of the standard test report reads:
“Resistance of earth continuity conductor at all points of consumption – Compliant.”
This test is different from the bonding test covered in Part 5.
An earth continuity conductor connects the consumer’s earth terminal to exposed conductive parts of the installation and provides a path for fault current.
Clause 8.6.3 requires the resistance of this path to be determined between the earth terminal of the distribution board under test and the earthing terminals of all points of consumption and switches supplied from that distribution board.
Why is this important?
An earth conductor may be physically connected but still have excessive resistance.
Loose terminals, damaged conductors, incorrect joints or poor connections can increase the resistance of the earth continuity path.
During an earth fault, the protective system relies on an effective earth path to allow sufficient fault current to flow so that the protective device can disconnect the supply.
This is why Test 2 requires more than confirming that an earth wire is present. The resistance of the earth continuity path must comply with the requirements of the standard.
What must be confirmed?
The registered person must establish that:
- An effective earth continuity path exists from the distribution board earth terminal to all required points.
- The earthing terminals of all points of consumption and switches supplied from the distribution board are tested.
- The measured resistance does not exceed the applicable value in Table 8.1.
- All socket-outlets are tested using an inserted plug so that the earth-pin resistance is included.
- Where direct measurement is impractical, the alternative permitted by Clause 8.6.3 is correctly applied.
- Earth continuity conductors and their connections comply with Clause 6.12.1.
Clause 6.12.1 also requires earth continuity conductors to be protected against tampering and damage. A wireway may not be used as an earth continuity conductor, and a fuse or switching device may not be installed in it.
How is the test carried out?
Start at the earth terminal of the distribution board being tested.
Measure the resistance between this earth terminal and the earthing terminal of each point of consumption and switch supplied from that board.
Compare the results with Table 8.1, which specifies the following maximum resistance values:
| Protective device rating | Maximum resistance |
| 6 A | 1,533 Ω |
| 10 A | 0,920 Ω |
| 16 A | 0,575 Ω |
| 20 A | 0,460 Ω |
| 25 A | 0,368 Ω |
| 32 A | 0,288 Ω |
| 40 A | 0,230 Ω |
| 45 A | 0,204 Ω |
| 50 A | 0,184 Ω |
| 63 A | 0,146 Ω |
For final circuits with a rated current greater than 63 A, Clause 8.6.3 refers to Table 6.28, which deals with earth continuity conductor sizes and maximum circuit lengths.
It is important not to confuse this test with Test 1. The 0,2 Ω limit specified for bonding does not automatically apply to every earth continuity conductor. For Test 2, the applicable requirements of Clause 8.6.3 must be used.
There is also a specific requirement for socket-outlets. Every socket-outlet must be tested by inserting a plug, with the resistance of the earth pin included in the measurement.
Testing only at the earth terminal behind the socket-outlet does not satisfy this requirement because it excludes the earth-pin connection.
Where it is not practical to measure the resistance directly, Clause 8.6.3 permits the suitability of the earth continuity conductor to be confirmed by an earth loop impedance test at the point of consumption, in accordance with Clause 8.6.5.1.
For embedded generator installations, relevant earthing terminals can include inverter or power-converter enclosures, a.c. and d.c. surge protective devices, and PV module and mounting bonding arrangements.
Common mistakes
Common mistakes include:
- Taking one earth continuity reading and assuming the entire installation complies.
- Testing only a few convenient socket-outlets instead of every required point.
- Testing behind a socket-outlet without including the earth-pin connection.
- Using the 0,2 Ω bonding limit instead of the applicable Table 8.1 value.
- Using the incorrect protective-device rating when selecting the maximum permissible resistance.
- Forgetting the earthing terminals of switches supplied from the distribution board.
- Accepting a continuity buzzer as proof without determining the resistance.
- Ignoring loose, damaged or corroded earth connections.
- Applying Table 8.1 to final circuits above 63 A instead of the relevant Table 6.28 requirements.
What if the result is unacceptable?
An excessive resistance reading or an open earth continuity path must be investigated.
Check the conductor, terminals, joints, glands, armouring connections and other parts forming the earth continuity path. Repair or replace the defective part and repeat the test.
Where the fault could have affected other test results, Clause 8.6.1 requires those tests to be repeated as well.
Regulation 9(3) of the Electrical Installation Regulations requires the registered person to refuse to issue the Certificate of Compliance until the fault or defect has been rectified.
Practical tip
Do not ask only:
“Is there an earth wire?”
Ask:
“What is the resistance of the complete earth path from this point back to the distribution board, and does it comply with the limit for the protective device?”
Key takeaway
Earth continuity is not proved simply because an earth conductor is visible or a meter beeps. The complete earth continuity path must be effective, and its resistance must comply with the applicable requirements of SANS 10142-1.
Where this information comes from
This article is based on SANS 10142-1:2026 Edition 3.3, particularly Clauses 6.12.1, 6.12.3, 8.6.1, 8.6.3 and 8.6.5.1, Table 8.1 and the standard test report. The requirement concerning defects before certification is taken from Regulation 9(3) of the Electrical Installation Regulations, 2009.
