What Is an Electrical Installation Tester? Types and Selection Criteria
An electrical installation tester verifies an installation's protection by measuring RCD tripping time, loop impedance, insulation resistance and socket wiring.
An electrical installation tester is a device that makes verification measurements in a low-voltage installation, such as the tripping current and time of a residual current device (RCD), loop impedance, insulation resistance, protective conductor continuity and socket wiring. It is used when commissioning a new installation, after renovation and in periodic inspection to show with measured values that the protection scheme works.
Types
| Type | What it does | Example in the catalog |
|---|---|---|
| Multifunction installation tester | Combines several inspection measurements (such as insulation, continuity, loop impedance, RCD) in one device; the function list varies by model | UNI-T UT593, UT595 |
| RCD tester | Measures the RCD's tripping time and tripping current | UNI-T UT582+, UT586+ |
| Leakage current and insulation megohmmeter | Combines RCD testing with insulation resistance measurement | UNI-T UT526 |
| Socket tester | Shows the socket's wiring status and whether the protection trips | UNI-T UT07B-EU |
Measurements and selection criteria
- RCD test: The tester must support the rated residual current (IΔn; such as 10, 30, 100, 300 mA) and type (AC, A, B) of the RCD to be tested. At ½ IΔn the RCD must not trip; at 1 IΔn and 5 IΔn the tripping time is measured, and a ramp test finds the actual tripping current. A general-type RCD must trip within 300 ms at IΔn and within 40 ms at 5 IΔn; selective (S) types have longer times. A starting angle of 0° and 180° lets the time be measured on both half-cycles of the mains waveform.
- Insulation resistance: The test voltage is 250, 500 or 1000 V DC. On 230/400 V circuits the measurement is made at 500 V DC and the value must be at least 1 MΩ.
- Loop impedance and fault current: Shows whether the protective device will trip fast enough in a fault. On an RCD-protected circuit the measurement can trip the RCD; for these circuits check whether the tester has a no-trip (low-current) loop test.
- Continuity: The resistance of protective conductors and equipotential bonding is measured with a test current of at least 200 mA.
- Measurement category: The tester's CAT rating and voltage must cover the measuring point; for example, the UT586+ is CAT III 600 V.
Common mistakes
- Testing an RCD only with its test button: The button shows that the RCD trips but does not measure tripping time or current.
- Testing a type A RCD with sinusoidal current only: Its response to pulsating DC residual current is only shown with a type A test current.
- Measuring insulation on a live circuit or with electronics connected: The measurement is made on a de-energised circuit; if drives, surge protectors and meters are not disconnected, the test voltage damages them or distorts the result.
Related standards
- IEC 60364-6: Initial and periodic verification of low-voltage installations; it contains the insulation resistance limits.
- IEC 61557 series: For the testers themselves: part 2 insulation resistance, 3 loop impedance, 4 protective conductor continuity, 6 RCDs, 10 multifunction devices. Check the model's conformity in the manufacturer's datasheet.
- IEC 61008-1 and IEC 61009-1: Tripping time limits for RCDs.
Installation testers in the catalog
The Electrical Installation Testers category lists 6 active products, all from Unit: the UT593 and UT595 multifunction installation testers, the UT582+ and UT586+ digital RCD testers (UT586+ 10–1000 mA, CAT III 600 V), the UT526 leakage current and insulation megohmmeter and the UT07B-EU socket tester. The UT07B-EU and UT586+ are sold on a quote basis; the other four can be added to the cart.
For insulation measurement only see Insulation Resistance Testers, and for earth resistance Earthing Measuring Instruments.
Frequently asked questions
Is a socket tester enough for an installation inspection?
No. A socket tester shows the wiring and whether the protection trips, but not every wiring fault; tripping time, loop impedance and insulation resistance are measured with an installation tester.
Why does the RCD trip during a loop impedance test?
The test current flows between phase and the protective conductor and can exceed the RCD's rated residual current. On RCD-protected circuits use the tester's no-trip loop test mode.
What is the difference between an installation tester and a megger?
A megger measures only insulation resistance. An installation tester also performs measurements such as RCD, loop impedance and continuity.