How to Perform IMD, SPD, and Voltage Drop Tests with the Fluke 1674 FC

When your day is filled with inspecting, testing, and troubleshooting electrical installations, the Fluke 1670 Series Multifunction Installation Testers can make your job easier. The 1670 Series testers are built to comply with IEC 60364-6 and all relevant local installation test standards, ensuring you can perform your tasks quickly, efficiently, and with confidence in residential, commercial, and industrial environments.

This guide explains how to perform IMD, SPD, and Voltage Drop testing with the Fluke 1674 FC — and shows how our Auto Test function can save time compared to manual testing.

What Is Insulation Monitoring Device (IMD) Testing?

Insulation resistance is a crucial test for ensuring the safety and reliability of electrical installations. IMD testing monitors the insulation resistance of IT (unearthed) systems and issues an alarm if resistance drops below a set threshold. This helps prevent electrical hazards and ensures compliance with IEC safety standards.

IMD Testing Step by Step with the Fluke 1674 FC

1. Select the IMD option on the main menu.
2. Choose the appropriate resistance value by tapping the icon on the left side of the screen (1 kΩ to 500 kΩ) based on your system requirements. (If you use the scroll wheel, select the value and then press ENTER to confirm your selection.)
3. Push TEST to start the timer for the IMD measurement.
4. If the IMD alarm does not indicate a failure, push TEST to stop the stopwatch.
5. Repeat the steps to change the response resistance until the alarm indicates an insulation failure. When the alarm indicates a failure, push TEST to stop the stopwatch.

What Is Surge Protection Device (SPD) Testing?

Surge Protection Devices (SPDs) protect electrical installations from high voltage peaks that can damage equipment. Testing ensures that SPDs maintain high impedance under normal conditions and respond correctly to surges.

SPD Testing Step by Step with the Fluke 1674 FC

1. Choose the SPD option on the main menu.
2. Set inputs and voltage range by selecting L-N, L-PE, N-PE, and either 500 V or 1000 V on the left side of the screen, based on your testing requirements.
3. Push and hold TEST to start the SPD measurement. The test voltage ramps up toward the pre-set value but will stop at the point where the SPD starts to conduct and reaches the maximum allowed test current of 1 mA. This prevents SPD damage during testing.
4. When the test is completed, the result is displayed in both VDC and VAC representative values on the screen.
5. After the measurement is finished, wait until the device under test is fully discharged.

What Is Voltage Drop Testing?

Voltage drop testing measures the expected voltage drop in volts and as a percentage from the reference point (usually the distribution board) to a specific outlet. This ensures that voltage levels remain within acceptable limits, as specified by IEC 60364-5-52 standards. All three of the Fluke 1670 Series Multifunction Installation Testers — the 1672, 1673 FC, and 1674 FC — perform voltage drop testing.

Voltage Drop Testing Step by Step with the Fluke 1670 Series Testers

1. Ensure your test leads are zeroed for accurate measurements.
2. Choose the appropriate circuit design nominal current from the selection field (6 A to 40 A).
3. Perform a test at the reference point (for example, the distribution board) to obtain reference values.
4. Push TEST to start the ZREF measurement.
5. Test outlets by pushing TEST again for each individual outlet or connection point.
6. Verify that the voltage drop is within acceptable limits (less than 4%). Set user-defined limits if required.

What Is Auto Test?

Auto Test is a sequence of tests set to run automatically in a selected order when launched with a single press of TEST. The Fluke 1673 FC and 1674 FC testers have three pre-set sequences for tests that are used most often; the testers also allow you to customize the sequence to your particular needs with user-programmable settings. The results of an Auto Test sequence show in a table that updates each time a measurement is completed.

1. Auto Test saves time by performing required tests up to 30% faster than testing with manual setups — which adds up quickly, especially on large-scale projects.
2. Auto Test reduces the chance of manual errors by automating the test sequence for more consistent and reliable results.
3. Auto Test is easy to use — it runs a complete test sequence with just the touch of a button, making even complex tasks easier for less-experienced technicians.
4. Auto Test performs comprehensive testing, including continuity, insulation resistance, loop impedance, RCD, polarity, and earth resistance tests. It completes all necessary checks with no missed steps.
5. Auto Test provides immediate feedback through immediate visual pass/fail indications, helping you identify and address issues quickly.

Note: The automatic test sequence will trip an RCD. Because an insulation test is part of the sequence, make sure that no appliances are connected to the circuit under test.

Running a Preset Auto Test Step by Step with the Fluke 1673 FC or 1674 FC

Auto Test presets enable you to run the most often-used tests quickly and efficiently, making it easier for even less-experienced technicians to test with confidence.

1. Select the AUTO TEST mode.
2. Connect the mains test cord to the tester.
3. Before you do a loop impedance test, zero the test leads.
4. Plug the mains test cord into the socket under test.
5. Select the RCD type and test type.
6. Select the nominal RCD fault current.
7. Press TEST.
   The primary display shows the Loop impedance Z, or the Line impedance Z. The secondary display shows the PEFC or the PFC (k). The RCD will trip, and the Tester shows the trip current, and then the trip time. The insulation tests start, and you see the results when each test is done. A beep sounds with each completed test. Note that you cannot override the Safety Pretest warning because the insulation Safety Pretest is active. If the insulation Safety Pretest detects a connected appliance, the test sequence stops.
8. When the test is done, reset the RCD.
9. Test results are located in temporary memory. If you want to store the test results for later recall, press SAVE.

User-Programmable Auto Test with the Fluke 1674 FC

The programmable Auto Test on the Fluke 1674 FC is a custom automatic test sequence that gives you the versatility to choose the test order, pause a test, and restart a test. It offers three custom-configurable Auto Test sequences that you can set up according to your particular requirements, such as energizing, de-energizing, or manipulating a circuit before you finish the complete sequence of measurements.

To create or edit a custom Auto Test:

1. Push FUNCTION.
2. Select Auto Test.
3. Select the custom number you want to save the auto sequence to. If the custom sequence contains saved tests, the details show on the left side of the display. This area is empty if no tests are assigned.

To add a new test:

1. Select Add Function and choose the function to add from the pop-up list.
2. Select the settings.
3. Tap 2 to exit the setup screen.

Repeat these steps to add more tests.

To edit or remove a function:

1. Select the test.
2. Change the settings or select Remove Function.

Greater Efficiency with Fluke Accuracy

Fluke 1670 Series Multifunction Installation Testers are designed to help you unlock greater efficiency and precision in your electrical testing workflows and simplify compliance with IEC 60364-6 and local installation test standards. Using powerful features like Auto Test, Fluke Connect™ (1673 FC and 1674 FC), and TruTest™ software, you can save time and deliver results with the confidence that comes from Fluke accuracy and reliability.