What Is Portable Appliance Testing (PAT)?
Portable Appliance Testing (PAT) is the process of testing electrical appliances to ensure they are safe for continued use. In Australia, PAT testing is governed by the AS/NZS 3760 standard and involves both visual inspection and electrical testing using specialised equipment.
While the term "test and tag" is more commonly used in Australia, PAT testing is the internationally recognised term for the same process. Every year in Australia, PAT testing prevents thousands of potential electrical incidents by identifying equipment defects that are invisible to the naked eye.
Equipment Used in PAT Testing
Portable Appliance Testers
A PAT tester is a specialised instrument that performs the electrical tests required by AS/NZS 3760. Key features include:
- Earth continuity testing � measures the resistance of the earth path
- Insulation resistance testing � measures resistance between conductors and earth
- Leakage current testing � measures current flowing through the earth during operation
- Polarity testing � verifies correct conductor connections
- RCD testing � some PAT testers include RCD trip time testing
- Data storage and download � stores test results for electronic record-keeping
- Barcode/QR scanning � for efficient asset identification
Calibration Requirements
PAT testers must be calibrated at least annually by a NATA-accredited laboratory. Using an uncalibrated tester may produce inaccurate results, which could lead to unsafe equipment being passed or safe equipment being unnecessarily failed.
PAT Testing Procedures
Step 1: Visual Inspection
Before any electrical testing, a thorough visual inspection must be performed. Check for damaged or frayed power cords, cracked or broken plug housings, bent or missing pins, signs of overheating, moisture ingress or corrosion, missing or loose screws, and correct fuse rating. An estimated 80% of faults can be identified through visual inspection alone.
Step 2: Earth Continuity Test
This test verifies that the earth conductor from the plug to the equipment chassis has sufficiently low resistance. The maximum allowable resistance is typically 1 ohm for most Class I equipment.
Step 3: Insulation Resistance Test
A 500V DC test voltage is applied and the resulting resistance is measured. The minimum acceptable insulation resistance is 1 megohm for most equipment.
Step 4: Leakage Current Test
Some testing regimes include a leakage current test, which measures the actual current flowing through the earth conductor while the equipment is operating normally.
Step 5: Polarity Test
For extension leads and cord assemblies, a polarity test verifies that the active and neutral conductors are correctly connected throughout the lead.
Pass and Fail Criteria
Pass Criteria
- Visual inspection � no visible damage or defects
- Earth continuity � resistance below 1 ohm
- Insulation resistance � above 1 megohm
- Leakage current � below 5mA for Class I, below 0.5mA for Class II
- Polarity � correct conductor connections
Fail Criteria
Any of the following constitutes a fail: visible damage affecting safety, earth continuity above 1 ohm, insulation resistance below 1 megohm, excessive leakage current, incorrect polarity, or an RCD that fails to trip within the specified time. Failed equipment must be immediately removed from service.
Tag Colour Systems
While AS/NZS 3760 does not mandate a specific colour system, many Australian states use colour-coded tags:
- January, February, March � Red (Q1)
- April, May, June � Green (Q2)
- July, August, September � Blue (Q3)
- October, November, December � Yellow (Q4)
Choosing a PAT Testing Provider
When selecting a provider, ensure they use calibrated PAT testers with current certificates, employ competent technicians, provide detailed test reports and asset registers, offer digital record-keeping, carry appropriate insurance, and can provide references from similar businesses.
Conclusion
Portable Appliance Testing is a proven method for identifying electrical faults before they cause harm. By understanding the testing process, the equipment used, and the pass/fail criteria, Perth businesses can make informed decisions about their compliance programs.