⚡ SANS 10142 Testing Principles Series

Test 1: Continuity of Bonding — The Test That Proves Metal Parts Are Electrically Together

Introduction

Before we talk about readings, instruments, and limits, we need to understand the purpose of this test.

Continuity of bonding is not just a “tick-box test” on the COC. It proves that exposed and extraneous conductive parts that could become dangerous are connected together so that they remain at substantially the same electrical potential.

In simple terms:

👉 If a fault happens, bonding helps prevent two metal parts from sitting at different voltages where a person could touch both and become the path between them.

SANS 10142-1 requires the continuity of bonding conductors to be confirmed between exposed conductive parts within arm’s reach of each other, and where an instrument is used, it must operate between 4 V and 24 V AC or DC with a test current of at least 0.2 A. The resistance must not exceed 0.2 Ω.

🧠 1. Foundation (Understanding): What Are We Actually Testing?

For the electrician building a solid foundation, think of bonding like this:

Bonding is the electrical “joining together” of metal parts so that they are at the same potential.

Examples may include:

Water pipes, metal roofs, gutters, downpipes, antennas, exposed conductive parts, pumps, and other services where bonding is required. TDMI’s training material identifies bonding topics under SANS 10142-1 clause 6.13, including hot and cold-water systems, antennas, roofs, gutters, downpipes, waste pipes, water pumps, and other services.

The key understanding is this:

✅ You are not testing whether the circuit works
✅ You are not testing earth leakage
✅ You are not testing insulation resistance

👉 You are testing whether the required bonded metal parts are electrically continuous with one another

The pass limit is simple:

👉 Resistance must not exceed 0.2 Ω

That is why your test leads matter. Your instrument matters. Your connections matter.

🛠️ 2. Application (Doing): How Must the Test Be Done?

At this level, the electrician must move beyond “I got a beep.”

A continuity buzzer can help you identify a connection, but this test requires a measured resistance value.

The instrument requirement is critical:

Your test device must have:

✅ No-load voltage between 4 V and 24 V AC or DC
✅ Test current of at least 0.2 A
✅ Ability to measure low resistance accurately
✅ Leads in good condition
✅ Zeroed or compensated leads before testing

A proper method includes:

Identify all parts that require bonding
Confirm the bonding conductor is present and secure
Use the correct low-resistance tester
Zero or compensate test leads
Test between relevant bonded parts
Record the result
Confirm the reading is 0.2 Ω or less
If it fails, rectify and retest

And very importantly:

👉 If the test fails, the fault must be corrected and the test repeated
👉 Any affected tests must also be redone

⚡ 3. Mastery (Owning Responsibility): What Are the Limitations?

This is where professionalism separates from shortcuts.

A good reading does not automatically mean the whole installation is compliant.

It only proves continuity at the points tested.

The professional must ask:

👉 Was the correct part bonded?
👉 Was bonding required in that location?
👉 Is the conductor correctly sized?
👉 Is it mechanically secure?
👉 Is it protected from tampering or damage?
👉 Is the clamp suitable?
👉 Is the connection permanent?
👉 Was the surface clean enough to ensure proper contact?
👉 Could corrosion affect the connection later?
👉 Did I test all relevant points—or only the easy ones?

TDMI’s training material highlights that a bonding conductor must be at least 2.5 mm² copper or equivalent and arranged so that it cannot be tampered with.

That means a low resistance reading on a poor, temporary, loose, painted, corroded, or undersized connection is not enough.

The professional does not only ask, “Did my tester beep?”

The professional asks:

👉 “Will this bonding still be effective when a fault happens?”

⚠️ Common Mistakes Electricians Make

Using a multimeter beep test only
Not zeroing test leads
Testing only one bonding point
Not recording actual results
Testing on painted or corroded surfaces
Ignoring loose clamps
Failing to inspect mechanical integrity
Not understanding which parts require bonding

💡 Final Thought

Continuity of bonding is the first test for a reason.

It confirms one of the most basic safety principles in an electrical installation:

👉 Metal parts that can become dangerous must be electrically connected together so that fault conditions do not create unnecessary risk.

At TDMI Training, we train electricians to understand the test, not just perform it.

Because when there is no understanding, shortcuts become easy.

But when you understand the purpose, the method, and the limitations…

There is only one standard:

✅ Test properly
✅ Record correctly
✅ Rectify failures
✅ Sign responsibly

SANS 10142 Testing Principles Series (1)