Extension Leads: The Most Failed Item in Any PAT Test

Ask an engineer which item fails most, and the answer is rarely an appliance. It is the extension lead nobody has looked at in four years.

Why they fail so often

• They live on the floor. Chair castors, trolleys and feet crush the cable repeatedly at the same point.
• They get moved constantly. Every move flexes the conductors at the plug and socket entry — the classic failure point.
• Nobody owns them. A kettle belongs to the kitchen. An extension lead belongs to no one, so no one inspects it.
• They get daisy-chained. One lead plugged into another multiplies the load on a single 13A plug.
• They are bought on price. Cheap leads use thin conductors that overheat under load.

An extension lead is an appliance

This is the part people miss. A four-gang extension lead is a separate item requiring its own asset ID, its own test and its own label. So is every IEC “kettle lead” behind a monitor or printer. If your previous report lists 40 items for an office with 40 desks, the leads were almost certainly not counted — and that is where the faults are.

What testing an extension lead involves

Earth continuity along the full length, insulation resistance, polarity — checking live and neutral have not been reversed, which is common in rewireable plugs — and a load check on the fuse rating. A lead that passes at the plug can still fail along its length where it has been crushed.

The daisy-chain problem

A 13A plug supplies a maximum of about 3kW. Two four-gang leads chained together still draw through that single plug. Put a 2kW heater and a 1.5kW kettle on the chain and you are over the limit, drawing through a cable that may be rated at 5A. Cable-drum extension leads make this worse — coiled cable cannot dissipate heat, and the drum rating drops sharply when it is not fully unwound.

Practical steps that cost nothing

1. Count them honestly before booking a test, including IEC leads.
2. Stop the chaining. One lead into one wall socket, never lead into lead.
3. Unwind cable drums fully before use, every time.
4. Route them out of traffic — along skirting, not across a walkway.
5. Bin the damaged ones. A replacement costs a few pounds. A repaired flex on a lead that is already been crushed is a false economy.
6. Look at them monthly. Most faults are visible — a nick, a flattened section, scorching at the plug.

We test every lead on site as an item in its own right and record it individually. Ask what your true item count is.