Loop & RCD Testers

A loop tester and RCD tester are essential electrical tools used to verify the safety and integrity of an electrical circuit.

Loop testers and RCD testers can work in tandem. An RCD (Residual Current Device) is capable of breaking an electrical circuit before it causes harm, whereas a Loop Tester is a quick, convenient and highly specific method of evaluating an electrical circuit for its ability to engage protective devices (circuit breakers, fuses, Ground-fault circuit interrupter).

These instruments consist of test leads and probes to connect to the circuit under test, along with an intuitive display to show test results. Loop testers and RCD testers are critical tools for professionals in the electrical industry, enabling them to assess the safety, compliance, and performance of electrical circuits and protective devices. By utilising these testers, electricians, electrical engineers, safety inspectors, facility managers, and maintenance technicians can ensure electrical systems are operating safely and within regulatory standards.

Functionality of Loop & RCD Testers

Both loop testers and RCD testers are critical tools for professionals in the electrical industry, enabling them to assess the safety, compliance, and performance of electrical circuits and protective devices.

The primary function of a loop tester is to verify that if an earth fault occurs, sufficient current will flow to operate the protective fuse or circuit breaker within a predetermined time. An impedance tester ensures the circuit is disconnected fast enough to prevent overheating and the risk of fire, a key part of earth fault loop testing.

An RCD tester checks the functionality of a Residual Current Device—which is a generic term applied to a family of products which open automatically in response to a residual current equal to or greater than the RCD's rated residual operating current. The RCD tester confirms the device can rapidly and automatically disconnect the electrical supply upon detecting an unbalanced current, a life-saving function that offers personal protection against fatal shocks if you touch something live, (e.g. bare wire).

Together, loop testers and RCD testers ensure a circuit's protective devices work correctly. They provide confidence that electrical systems are operating safely and within regulatory standards for all of New Zealand's properties.

Types of Testers

Earth Loop Impedance Testers

An earth loop tester, also known as an impedance tester, measures the resistance of the earth fault loop. It is essential for verifying that, in the event of an earth fault, sufficient current will flow to disconnect the power quickly, preventing overheating and fire. Electricians in New Zealand use them to ensure installations meet wiring regulations.

RCD Testers

A dedicated RCD tester checks the operational integrity of Residual Current Devices. It confirms that the RCD can trip within the required time (typically 30ms or less) and at the correct current, ensuring personal protection from electric shock. Professionals and homeowners in New Zealand use these devices to ensure RCDs are fully functional.

Combined Loop & RCD Testers

A single instrument that performs both loop impedance and RCD tests is a combined tester. This all-in-one tool is a convenient and efficient solution for electricians in New Zealand who need to perform comprehensive circuit verification quickly, providing a unified approach to earth fault and shock protection testing.

High-Current & Non-Trip Loop Testers

Specialised loop testers are available for specific test scenarios. High-current models perform tests with a brief, high-amperage pulse, whereas non-trip models use a low-current method to test the earth fault loop without tripping the RCD. These are useful when you need to perform an impedance test on a circuit that is protected by an RCD without causing an unwanted power outage.

Factors to Consider while Choosing the Right Loop & RCD Testers

Selecting the right loop tester or RCD tester is important for ensuring accurate and compliant electrical testing. Consider these factors when choosing your impedance tester in New Zealand:

Required Tests: Match the tester to the specific tests needed. Combined loop testers and RCD testers are efficient for comprehensive circuit checks. An impedance tester is required for earth fault loop verification, while a dedicated RCD tester is for RCD performance.
Non-Trip Requirement: Choose a loop tester with a non-trip feature. A non-trip impedance tester performs an earth fault loop test without tripping the RCD, which is a key feature for live circuits in domestic or commercial buildings.
Test Current Range: Ensure the tester’s current range is suitable for the circuit you’re inspecting. Impedance testers may have high-current or low-current modes to accommodate various circuit characteristics.
Accuracy Needs: The accuracy of the tester is vital for compliance. Higher accuracy is needed for official reporting in New Zealand, while a simple pass/fail tester may suffice for quick checks.
Safety Ratings: Always select a tester with a CAT rating (e.g., CAT II, CAT III) that is suitable for the voltage and application you are working in. A correct safety rating provides protection against transient voltages.
Display & Interface: A clear display with a good interface improves efficiency on the job. Digital testers with backlit screens, data logging, and auto-ranging features make readings faster and more reliable.
Calibration & Support: In New Zealand, look for brands that offer local calibration services and strong technical support. Regular calibration of your tester ensures its long-term accuracy and compliance.

Industrial Applications of Loop & RCD Testers

Loop testers and RCD testers are indispensable tools for ensuring electrical safety and compliance across a wide range of industries in New Zealand.

Domestic, Commercial & Industrial Installations: Electricians in New Zealand use loop testers to verify earth fault loop impedance in new and existing installations. They confirm that earth protection is correctly installed and that a fault will be cleared within the required time.
Live Testing During Maintenance: RCD testers are used during routine maintenance to check the tripping time and current of RCDs. This is a key check to ensure the device will respond quickly enough to prevent electric shock when a live conductor is accidentally touched.
Regulatory Compliance Checks: A combined loop tester and RCD tester is the primary tool for compliance checks. Professionals use it to verify installations against New Zealand’s AS/NZS 3000 Wiring Rules, providing peace of mind and formal reports.
Fault Finding and Troubleshooting: When a circuit trips unexpectedly, loop testers and RCD testers help electricians quickly identify the specific earth fault or wiring issue. They provide clear data on the fault type, allowing for swift and accurate repairs.
Appliance Testing (PAT): Portable Appliance Testers (PAT) often include RCD tester functionality. Appliance testers are used in New Zealand for checking the safety of portable appliances, ensuring that the RCD protection in a power outlet is functioning correctly.

Why choose RS for your Loop and RCD Testers?

RS New Zealand is a trusted supplier and distributor of comprehensive loop & RCD testers and electrical safety solutions. We offer a wide range of loop testers and RCD testers sourced from reputable brands like Megger, Gossen Metrawatt, and Kewtech Corporation, ensuring reliable options for every testing task.

Beyond loop & RCD testers, we also provide a wide array of other electrical testing & measurement tools, such as insulation testers, voltage testers, and PAT testers, catering to all your electrical inspection and compliance requirements.

Explore our user-friendly online site for the full range of products and have them shipped to your door at your convenience. With our flexible delivery options, you can receive your products precisely when needed. For comprehensive details on delivery times and fees, please consult our Delivery page.