9.2 Continuity of Earthing & Protective Bonding

Purpose of the Continuity Test

After visual inspection, the next classic dead test is continuity of the protective earthing system and equipotential bonding (AS/NZS 3000 region 8.3.5—confirm in your permitted edition). The question this test answers is simple and non-negotiable:

Is there a continuous, low-resistance metallic path from every required earthed/bonded part back through the protective earthing network to the main earthing point / MEN arrangement?

If that path is open, high-resistance, or misconnected, fault protection by automatic disconnection of supply (ADS) is compromised. Exposed conductive parts can remain at dangerous potential under fault conditions because fault current cannot return reliably through the intended earth–neutral path.

AS/NZS 3017 elaborates practical probe points, instrument technique, and interpretation consistent with Section 8 outcomes. Exam stems test the principle and sequence more than brand-specific meter menus.

What Must Be Continuous

Think of continuity as a network, not a single wire.

Protective earthing conductors (PECs)

• Continuity from each circuit’s earthing conductor (socket earth pins, switchboard earth bar tails, fixed-equipment earth terminals) back to the earth bar / main earthing point
• No reliance on random metalwork that is not intentional protective earthing

Main earth and MEN link path

• Continuity of the main earthing conductor to the electrode connection (as applicable)
• Integrity of the path that includes the MEN link at the main switchboard main earthing point—visual presence of a link is necessary but not sufficient; the related conductors must also be continuous and tight
• No “open MEN” discovered only after energising if a dead continuity check could have caught a disconnected link or floating earth bar tail

Equipotential bonding

As applicable to the installation:

• Bonding to water pipes, other service pipes, and structural steel or other extraneous conductive parts required to be bonded
• Continuity through bonding clamps and intermediate joints—painted, corroded, or isolated pipe sections can create open bonds that look fine until measured

Bonding limits potential differences between simultaneously accessible parts; it does not replace protective earthing, the MEN link, or ADS design. Continuity testing proves the bond is actually a conductor, not a decorative clamp.

Instrument Method

Dead test, low-resistance expectation

• Prove the circuit/installation section is de-energised and safe to work on before connecting the instrument
• Use an ohmmeter or the continuity function of a multifunction installation tester
• Expect a low resistance reading for a continuous path; an open circuit or unexpectedly high resistance is a fail until the joint, conductor, or connection is corrected and retested

Exact maximum continuity resistance values and any length/csa-dependent expectations must be taken from your permitted AS/NZS 3000 / 3017 text for the sitting. For exam strategy, prioritise: continuous + low resistance = pass path; open/high = defect.

Practical technique points (exam-relevant)

• Test from accessible equipment earth points and bonding points back to the earth bar / main earthing point as appropriate
• Account for parallel paths that can mask a broken intended conductor—interpretation skill matters when metalwork provides an alternative route
• Include both circuit PECs and main/bonding paths in a complete verification story

Fail Implications: ADS and Shock Risk

RCDs may still trip on residual current in some fault scenarios, but RCD presence does not excuse open protective earthing. Continuity failures remain serious non-compliance and shock risk.

Sequence: Dead Continuity Before Insulation (Where Appropriate)

EWRB Toolbox order after visual inspection:

1. Earth continuity (8.3.5)
2. Insulation resistance (8.3.6)
3. Polarity (8.3.7)
4. Correct connections (8.3.8)
5. Then live tests (EFLI 8.3.9, RCD 8.3.10)

Why continuity early?

• It is a dead test that proves the safety earthing network before applying IR test voltage and before energising
• Finding an open earth after energising is late discovery of a fault that should have been caught cold
• IR tests between live conductors and earth assume you understand the earth reference path; continuity establishes that the earth system is joined

Exam traps

• Treating continuity as “optional if IR is high”
• Confusing continuity ohms with insulation resistance megohms (different instruments, opposite desired magnitude)
• Thinking bonding continuity replaces the need for circuit PECs or MEN integrity
• Jumping to EFLI on a live board when earthing continuity has not been established

Study note

On a mental main switchboard sketch, trace: earth bar → main earthing conductor → electrode; MEN link to neutral; outgoing PECs to sockets; bonds to water/steel. Continuity testing is how you prove that sketch is real metal, not hope.