Electrical Testing Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Most Electrical Testing Engineer interviews in the UK follow a pattern, and knowing it beats guessing. Below are eight questions from our bank of 12, each with a note on what the interviewer is really after.

Eight Electrical Testing Engineer interview questions, and what the interviewer is thinking

1. What does the earth fault loop impedance test tell you, and how do you carry it out?

Why they ask: Loop impedance is a core test and they want to see you understand both purpose and method.

2. How do you test RCDs, and what results do you expect?

Why they ask: RCD testing is routine and failing to do it correctly can leave people at risk.

3. During an EICR on an occupied rented flat, you find a hazard that could cause immediate danger but the landlord's agent is pressing you to leave it off the report. What do you do?

Why they ask: They want to see whether you will resist commercial pressure and apply the regulations.

4. Tell me about a time you traced a difficult fault found during testing.

Why they ask: Test and inspection engineers have to diagnose why results fail, not just record them.

5. What is prospective fault current, and why do you measure it?

Why they ask: It checks you understand the protection and breaking capacity side of testing.

6. What is the scope of a periodic inspection, and how do you agree the extent and limitations with a client?

Why they ask: Extent and limitations drive the quality and legal value of a report.

7. You arrive to test a commercial premises and the client says you can't switch anything off because the business is operating. What do you do?

Why they ask: Testing normally requires isolation, and they want practical problem-solving.

8. Why did you choose testing and inspection as a specialism, and what qualities does it need?

Why they ask: They want to see that you value the role's responsibility.

A sample answer to question 1

What does the earth fault loop impedance test tell you, and how do you carry it out?

It shows whether the impedance of the earth fault loop, made up of the phase conductor, the earth path and the supply, is low enough for a protective device to disconnect the circuit quickly if a fault occurs. I measure it with a loop impedance tester at the furthest point of each circuit, after confirming that the installation is live and safe to test and that protective conductors are connected. Where an RCD would trip, I use a no-trip test setting. I compare the measured Zs to the maximum permitted values in BS 7671 for the type and rating of device, correcting for conductor temperature using the 80 percent rule when measuring cold. I also record Ze at the origin. A high reading points to loose connections, undersized conductors or a poor earth, and I investigate before certifying.

Common mistake to avoid: Reading the value without comparing it to limits; ignoring temperature correction

Want the rest?

Full model answers, key points and common mistakes for all 12 questions are on the Electrical Testing Engineer interview questions page. The first five are free, no sign-up needed.