Electrical basics and the limits

Electrical work is the area where the gap between what people attempt and what they should attempt causes the most serious harm.

The regulatory position

Which varies and is generally restrictive.

In most jurisdictions, certain categories of electrical work must be carried out or certified by a qualified person — new circuits, work in bathrooms and other special locations, and consumer unit replacement among them.

Other work may be permitted for a householder, subject to conditions.

Doing regulated work without certification can invalidate insurance, cause problems on sale, and most importantly be dangerous.

Checking the position in your own jurisdiction before starting anything is the first step.

Understanding the consumer unit

Worth knowing regardless of what you do yourself.

The main switch isolates the whole installation.

Circuit breakers protect individual circuits against overload and short circuit, and trip when either occurs.

Residual current devices detect an imbalance indicating current flowing to earth — through a person, for instance — and disconnect very quickly.

These are the devices that prevent electrocution, and modern installations have them on most or all circuits.

Knowing which breaker serves which circuit, and labelling them, takes an afternoon and is repeatedly useful.

When something trips

The diagnostic sequence.

Unplug everything on the affected circuit.

Reset the breaker.

Reconnect items one at a time, and the one that causes it to trip again is the fault.

A residual current device tripping generally indicates a genuine fault rather than an overload, and is more serious.

Repeated tripping with nothing connected indicates a fault in the fixed wiring, which requires an electrician.

Resetting a breaker repeatedly without finding the cause is not safe.

What a householder can generally do

Subject to local rules.

Replacing a plug or a fuse in a plug, where these are used.

Replacing a like-for-like light fitting or switch on an existing circuit.

Replacing a socket faceplate.

Resetting breakers and testing devices.

In each case: isolate the circuit at the consumer unit, verify it is dead with a tester, and work only when certain.

Switching off a light switch does not isolate a fitting, since the neutral remains connected.

What requires a professional

New circuits, additional sockets, and any extension of existing wiring.

Anything in a bathroom or shower room.

Anything outdoors.

Consumer unit work.

Any fault in the fixed wiring.

Anything where you are not certain.

The warning signs

Which warrant immediate attention.

Burning smells, scorch marks or discoloration around sockets and switches.

Sockets or plugs that are warm.

Buzzing or crackling.

Lights flickering or dimming when appliances start.

Repeated tripping.

Shocks or tingles from appliances or fittings.

Old wiring types — rubber or fabric insulation, round-pin sockets, a fuse board with rewirable fuses — which indicate an installation due for assessment.

Periodic inspection

Recommended at intervals that vary by property type and use, commonly around a decade for owner-occupied homes and more frequently for rented property, where it is a legal requirement in several jurisdictions.

An inspection produces a report identifying anything requiring attention, graded by urgency.

It is worth obtaining before purchasing a property and after any period of doubt.

Practical safety

Points that prevent the common incidents.

Do not overload extension leads, and be particularly cautious about high-power appliances such as heaters on extensions.

Do not run cables under carpets, where damage is invisible.

Unplug rather than switch off before working on any appliance.

Use a detector before drilling into walls, as discussed elsewhere on this site.

Keep water away from electrical fittings.

And replace damaged cables and plugs rather than taping them.

Signs an installation needs assessing

Which are worth recognising, since the alternative to noticing them is discovering the problem the hard way.

A fuse box with rewirable fuses or cast-iron switches, which indicates an installation that predates current protective devices entirely.

No residual current protection, which is the safeguard against electric shock and which older units lack.

Sockets or switches that are warm, discoloured, scorched or that crackle.

Lights that dim when an appliance starts.

Breakers that trip repeatedly with no identifiable cause.

Rubber, fabric or lead-sheathed cabling visible anywhere, which is long past its serviceable life.

And no record of any inspection, which for most domestic installations is recommended at intervals of around a decade, and more often for rented property.

Any of these warrants an electrical installation condition report from a registered electrician rather than a wait-and-see approach.

General information only, not professional advice. Electrical work is regulated and dangerous — consult a qualified electrician and follow local regulations.