What Causes an Appliance to Fail a PAT Test?
During a routine Portable Appliance Testing (PAT) inspection, finding a "FAILED" label stuck to an item of equipment can raise immediate questions for business owners, office managers, and duty holders.
What made the appliance fail? Can it be repaired? And what are your legal obligations for removing or replacing non-compliant equipment under UK workplace safety law?
While PAT testing certificates don't use the exact same complex codes as an EICR fixed wiring report (like C1 or C2), engineers follow strict IET Inspection & Testing Code of Practice criteria to log pass and fail statuses.
The Two Stages of a PAT Test Failure
Every appliance on your premises undergoes a two-part inspection. An item can fail at either stage:
- The Visual Inspection (Accounts for ~80% of Failures): Before any electronic testing equipment is attached, the engineer visually checks the plug, cable, casing, and environment.
- The Combined Electrical Test: Using a calibrated PAT testing meter, the engineer tests internal components that cannot be seen with the naked eye.
1. Common Visual Inspection Failures
Visual checks catch the vast majority of hazardous equipment in commercial workplaces and rented properties. Key visual failure points include:
| Defect Identified | Risk Factor | Common Cause |
|---|---|---|
| Damaged Cable Outer Sheath | High (Shock hazard) | Frayed cables, heavy equipment trailing over leads |
| Exposed Core Wiring | Critical (Immediate risk) | Cable pulled away from plug strain relief |
| Incorrect Fuse Rating | Medium (Overheating/fire) | Wrong fuse fitted (e.g., 13A fitted instead of 3A) |
| Cracked Plug Casing or Pins | High (Shock/Arcing) | Dropped equipment, physical impacts |
| Thermal Discoloration | High (Fire risk) | Loose connections inside plug, wall socket overload |
Crucial Rule: If an appliance fails its visual inspection, it automatically receives a FAIL status and will not be subjected to secondary electrical testing until repaired.
2. Combined Electrical Testing Failures
If the appliance passes visual checks, it moves to meter testing. The meter measures electrical characteristics against strict thresholds:
A. Earth Continuity Failure (Class I Appliances)
Class I equipment (such as kettles, microwaves, and metal-cased tools) relies on a protective earth conductor to prevent the outer metal casing from becoming live during a fault.
⚠️ Failure Cause: Broken earth wire inside the plug/lead or high resistance in the earthing path.
B. Insulation Resistance Failure
Insulation breaks down over time due to heat, age, moisture, or internal dust buildup. If insulation resistance drops below permitted limits, current can leak into the casing.
⚠️ Failure Cause: Moisture ingress, degraded internal wiring, or blown internal components.
C. Protective Conductor / Touch Current Failure
Measures unwanted electrical current leaking from the appliance while running under power.
⚠️ Failure Cause: Deteriorating internal electronics, faulty heating elements, or damaged noise suppression filters.
What Actions Must You Take When an Item Fails?
When a PAT engineer identifies a dangerous or failing appliance during a site visit, the following procedure is initiated:
Immediate Quarantine
A red "FAILED" label is attached, the asset is logged as failed, and it is quarantined to prevent accidental use.
Duty Holder Notification
You will be informed immediately of any high-risk failures discovered during testing.
Repair or Disposal
Equipment must either be formally repaired by a qualified person and re-tested, or permanently removed and recycled.
Documentation
Your final PAT Asset Register & Certificate will log all passed and failed items for compliance records.
Need Fast, Reliable PAT Testing for Your Site?
Keeping your workplace compliant doesn't have to interrupt your daily operations. At RC Compliance, our accredited engineers deliver clear asset tracking, transparent pass/fail reporting, and minimal disruption to your business.