I am an experienced and licensed electrician who often gets asked how to properly test and tag electrical installations in homes and apartments. Proper testing and tagging of domestic electrical work is crucial for safety, compliance, and liability reasons. In this comprehensive guide, I will walk you through the entire process step-by-step.
Understanding Electrical Installation Testing Standards
Before doing any electrical testing, it is critical to understand the relevant standards and regulations in your jurisdiction.
The main standard for domestic electrical installations in many countries is AS/NZS 3000, also known as the Australian/New Zealand Wiring Rules. This standard specifies the requirements for design, construction, and verification of electrical installations up to 1000V AC and 1500V DC.
Some key requirements from AS/NZS 3000 include:
- Insulation resistance testing - to detect any insulation breakdown
- Polarity testing - to verify correct polarity of active, neutral and earth
- Earth continuity testing - to ensure adequate earth paths exist
- Fault loop impedance testing - to verify automatic disconnection of supply
- RCD testing - to confirm operation of RCDs within prescribed trip times
Compliance with AS/NZS 3000 is mandated by law in most states and territories in Australia and New Zealand.
When Electrical Installation Testing is Required
As per AS/NZS 3000, testing and tagging of electrical installations is required in the following instances:
- For all new electrical installation work
- For additions, alterations and repairs to existing installations
- For second-hand electrical equipment prior to use
- Before re-energization of installation after changes
- For periodic testing of existing installations (every 5 years recommended)
Testing is necessary to verify that the installation is safe to energize and use.
Step 1 - Visual Inspection
The first step is a visual inspection of the electrical installation. This allows detection of any obvious faults or non-compliances.
I check the following during the visual inspection:
- Cables are properly supported and protected against damage
- Correct color coding of active (brown), neutral (blue) and earth (green/yellow) conductors
- Double insulation of cables enclosed in ducts and conduits
- Adequate IP rating of accessories for location (IP66 for outdoor, IP44 for bathrooms etc)
- Appropriate cable sizing for intended load as per AS/NZS 3000 maximum demand table
- Correct termination of cables into accessories
Any visual defects found are noted down for rectification before proceeding to testing.
Step 2 - Testing Power and Lighting Circuits
The next step is testing of power and lighting circuits. This includes:
Insulation Resistance Test
An insulation resistance test using a 500V megger is first done to measure insulation resistance between:
- Active and earth
- Neutral and earth
As per AS/NZS 3000, the insulation resistance must not be less than 1MΩ.
Polarity Test
A polarity test is done to verify that wiring has correct polarity:
- Active - Brown conductor
- Neutral - Blue conductor
- Earth - Green/Yellow conductor
I use a polarity tester or multimeter to check this.
Earth Continuity Test
An earth continuity test is done to measure resistance between exposed conductive parts and the main earth bar. This tests the earth path.
The earth continuity resistance should be less than 1Ω as per AS/NZS 3000.
Fault Loop Impedance Test
Next, a fault loop impedance test is done by injecting a test current and measuring the impedance in each circuit.
This verifies the automatic disconnection of supply in the required time under a fault condition. The measured impedance should not exceed the maximum prescribed in AS/NZS 3000.
Step 3 - Testing RCDs
RCDs (Residual Current Devices) are required for protection against earth leakage faults. AS/NZS 3000 mandates RCDs for power and lighting circuits.
RCDs must be tested by:
- Pressing the "Test" button to trip the RCD
- Checking the tripping time - should be less than 300ms
- Resetting then re-testing each RCD
Step 4 - Testing Smoke Alarms
Hardwired smoke alarms must also be tested by:
- Pressing the test button to trigger the audible alarm
- Checking connections are secure in the ceiling cavity
- Ensuring sufficient coverage of detectors as per AS 1670.6
Step 5 - Tagging
Once testing is completed, a tag must be securely attached at the main switchboard indicating:
- Date tested
- Name and license number of the testing electrician
- Type of tests performed and results
An additional periodic inspection and test tag can also be attached.
The tag serves as certification that the installation has passed the required tests.
Step 6 - Certificate of Electrical Safety
The final step is to issue a Certificate of Electrical Safety stating that the installation complies with AS/NZS 3000 and is safe to energize and use.
This certificate should be kept by the homeowner as proof of compliance.
I sign and endorse the certificate as the testing electrician. Copies are also kept for my records.
Conclusion
Thoroughly testing and tagging all electrical installation work is crucial for safety and compliance. By following the Australian/New Zealand Wiring Rules and industry best practices, I ensure that every electrical installation I test is safe for homeowners and tenants. Let me know if you need any electrical installation in your home or business tested and tagged by an experienced professional.