Selecting and using socket testers effectively

Categories of Socket Testers

Socket testers generally fall into two categories: simple and advanced. All types perform fundamental checks to confirm correct wiring of earth, line, and neutral connections. Results are typically indicated via LED’s, and in some models, an audible buzzer provides additional feedback.

For instance, the Martindale BZ101 (Buzz-It) Socket Tester is a widely used example. It not only identifies whether a socket is correctly or incorrectly wired but also uses a combination of visual and audible indicators to pinpoint the specific type of wiring fault.

All socket testers should detect the absence of an earth connection. However, advanced models provide further functionality by assessing the quality of the earth connection. These models are capable of measuring and indicating a value for earth loop impedance, a feature not available in simple testers.

For example, some recently introduced units such as the Martindale EZ365 and EZ165 will indicate you how good your earth is via earth loop impedance range indicators on the tester. Understanding the differences in the categories is important; simple socket testers have been seen to show an earth as ‘good’, even when the impedance is exceptionally high. Sometimes this is even at a level that is typically considered suitable for insulation; it’s clear that, in this case, the ‘protective’ earth will not protect.

Earth loop values higher than a few ohms can cause problems. For example, a reliable earth loop impedance indication is vital to ensure that some over-current protection devices react fast enough to avoid electrocution. Advanced testers such as the Martindale EZ365, which provide an earth loop impedance range indication, offer a more comprehensive assessment of electrical safety than basic LED-only testers.

Limitations of Socket Testers

It is important to note that socket testers cannot detect all fault conditions. There is one fault that a socket tester and, indeed, no other piece of equipment can easily find; the swapping of the Earth and Neutral wires. This is due to the earth and neutral being common at the substation (if not closer), so electrically, they are indistinguishable.

Furthermore, standard socket testers cannot identify reversed supply polarity (i.e., line and neutral reversed at the incoming supply). Detecting this serious fault requires a dedicated polarity test. Some advanced models, such as the Martindale BZ701, include this capability, which can be activated via a simple touchpad interface.

Additional Features

Other useful features available include an RCD test function to perform a basic trip test on a breaker associated with the socket under test. It should be remembered that this is a simple function test and does not replace the RCD test as part of BS7671 18th edition wiring regulations.

Many, even basic socket testers, include a buzzer to indicate the status of the socket, one advantage here is the tester can be used to help identify which socket is on which circuit in a similar way to a basic fuse finder. Using the buzzer as an indicator while activating the circuit.

Socket Testers for Industrial Applications

While much of the discussion has focused on standard three-pin domestic outlets, manufacturers also produce socket testers for industrial and commercial sockets, including four-pin and five-pin three-phase outlets. These testers typically perform the same fundamental checks as 13A models but are designed to accommodate different pin configurations, voltage and current levels. When selecting a tester for industrial use, it is critical to determine the specific testing requirements and consult the manufacturer’s specifications to ensure compatibility. Martindale offers a range of industrial socket testers suitable for various configurations.

Socket Testers to support electric vehicle charge points.

To support the ever-growing need for EV charging infrastructure the latest addition to the socket tester family is the dedicated EV socket tester. Units such as the Martindale BZ820-EV are designed to perform the same function as the simple electrical outlet tester, primarily basic wiring and voltage checks.

Compliance and Safety Considerations

Per BS 7671, any newly installed, repositioned, or repaired socket outlet must undergo appropriate verification procedures before being placed into service. These procedures include:

• Continuity testing of protective conductors and ring final circuits

• Insulation resistance testing

• Polarity checking

• Earth fault loop impedance measurement

For these tasks, electricians should use dedicated individual test instruments or multifunction installation testers.

It’s important to appreciate that socket testers are not an alternative to the complete verification of wiring installations. However, socket testers offer a fast and effective solution to identify potentially unsafe installations and wiring faults when correctly specified as a first-line indicator. They can also be helpful as a service tool in identifying potentially dangerous conditions before carrying out work on existing electrical systems and equipment, before installing new appliances or performing an initial check on sockets prior to full installation testing.

Visit: https://martindale-electric.co.uk/product-category/socket-testing/ for further information and tips.