# Earthing and Bonding: Two Different Jobs, Often Confused

> Earthing provides a deliberate low-impedance path to earth so that a fault current is large enough to operate the protective device quickly. Bonding connects exposed and extraneous metalwork together so that, during a fault, everything a person can touch simultaneously stays at a similar potential. They are complementary and neither substitutes for the other.

## Why it matters on a project

Earthing and bonding are the parts of an electrical installation that do nothing
at all until the day they are needed, and then determine whether a fault is an
inconvenience or an injury.

They are also the parts most easily damaged by subsequent work, because they
consist largely of conductors connected to metalwork that later trades cut,
move and replace.

## The two functions

| | Earthing | Bonding |
| --- | --- | --- |
| Purpose | Let fault current return so protection operates | Keep touchable metalwork at similar potential |
| Protects against | Prolonged fault, fire, equipment damage | Dangerous touch voltage during a fault |
| Connects to | Earth electrode system | Other metalwork and the main earth terminal |
| Failure mode | Protection does not operate fast enough | A person bridges two different potentials |
| Substitutes for the other? | No | No |

## What fit-out work tends to break

This is where the subject becomes practical for anyone running an interiors
project:

- A bonding conductor disconnected to move a pipe, not reconnected
- A metallic pipe section replaced with plastic, breaking continuity that
  something downstream relied on
- New metalwork — partitions, raised floors, trunking — installed without being
  brought into the bonding arrangement where required
- Earth conductors damaged or omitted at new distribution boards
- Earth pits built over, paved across or made inaccessible for testing

None of these produces a symptom. The installation energises and works. The
deficiency is only discovered by inspection and test, or by a fault.

## Common mistakes

- **Treating earthing and bonding as the same thing.** They protect against
  different events.
- **Disturbing bonding during fit-out without recording it.** What is not
  recorded is not reinstated.
- **Building over earth pits.** They need to remain accessible for testing and
  maintenance.
- **Testing once at handover and never again.** Earth resistance changes with
  ground conditions over time.
- **Improvising separate earths for IT equipment.** Without proper design this
  can create the hazard it was meant to avoid.
- **No test records at handover.** Inspection and test documentation is how
  anyone later knows what was actually installed.

## Standards referenced

Earthing practice in **IS 3043**; electrical installation practice in
**IS 732**; building services provisions in **NBC 2016, Part 8**. Earthing
system design, bonding requirements, test values and the testing regime for a
specific installation must be established by the project's electrical consultant
and verified by inspection and test.

## Frequently asked questions

### What is the practical difference?

Earthing is about clearing the fault — giving current a path back so the breaker or fuse operates fast. Bonding is about surviving it — making sure that while the fault exists, two metal things a person might touch at once are not at dangerously different voltages. A building can have a good earth and dangerous touch voltages if bonding is missing, which is why both are required.

### What has to be bonded?

Exposed conductive parts of the electrical installation, and extraneous conductive parts that could introduce a potential — typically metallic water and gas services where they enter, structural metalwork, and other incoming metallic services, connected in the manner required by the applicable wiring rules. What must be bonded in a specific installation is determined by the project's electrical consultant against IS 732 and IS 3043.

### Why do fit-outs cause earthing problems?

Because fit-out work cuts, moves and replaces metalwork. A bonding conductor disconnected to move a pipe and never reconnected, a metallic section replaced with a non-conductive one breaking continuity, or new metal partitions and raised floors installed without being considered — these are routine site events, and none of them announces itself. The installation looks finished and works normally until there is a fault.

### Does earth resistance need testing?

Yes, and periodically rather than once. Earth electrode resistance changes with soil moisture, corrosion and ground conditions, so a value measured at commissioning is not a permanent property. Testing practice and requirements are set out in IS 3043 and the applicable wiring rules, and the regime for a specific installation should be established by the electrical consultant.

### Is a separate earth needed for IT or sensitive equipment?

Arrangements for sensitive electronic equipment are a design matter and vary with the installation. What is important to understand is that creating isolated earth arrangements without proper design can introduce hazardous potential differences rather than remove noise. This should be designed by the electrical consultant against the applicable standards, not improvised on site to solve an equipment complaint.

## Sources

- [IS 3043](https://standards.bis.gov.in/website/published-standards/department-wise) — Code of practice for earthing
- [IS 732](https://standards.bis.gov.in/website/published-standards/department-wise) — Code of practice for electrical wiring installations
- [NBC 2016, Part 8](https://www.bis.gov.in/standards/national-building-code/?lang=en) — Building services — electrical installations

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Source: https://hagerstone.com/glossary/earthing-and-bonding