Air Conditioning Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Most Air Conditioning Engineer interviews in the UK follow a pattern, and knowing it beats guessing. Below are eight questions from our bank of 16, each with a note on what the interviewer is really after.

Eight Air Conditioning Engineer interview questions, and what the interviewer is thinking

1. Which refrigerants have you worked with, and how does global warming potential shape the choice of refrigerant on new installations?

Why they ask: They want to know you are current with refrigerants and the UK phase-down of high-GWP gases.

2. What does a typical day as an air conditioning engineer involve, and what do you enjoy most about the work?

Why they ask: They want to see realistic expectations of the mix of installation, maintenance and fault-finding.

3. Can you explain the vapour compression refrigeration cycle and what happens to the refrigerant at each stage?

Why they ask: It is the foundation of every diagnosis, so interviewers test whether you truly understand it.

4. Talk me through how you would commission a new split system after the pipework has been installed.

Why they ask: They want to see a methodical, standards-minded approach to installation quality.

5. How do you use superheat and subcooling when diagnosing a system, and what might low readings or high readings point to?

Why they ask: It separates engineers who can interpret readings from those who just top up gas.

6. A customer calls to say their office air conditioning is blowing warm air on the hottest day of the year. How do you approach the diagnosis?

Why they ask: They want to see structured fault-finding under pressure with a stressed customer.

7. What extra precautions apply when working with R32 and other A2L refrigerants?

Why they ask: As more systems use flammable-class refrigerants, employers need engineers who handle them safely.

8. Tell me about a difficult fault you diagnosed on an air conditioning system and how you reached the cause.

Why they ask: They need evidence that you can fault-find methodically rather than guess.

A sample answer to question 1

Which refrigerants have you worked with, and how does global warming potential shape the choice of refrigerant on new installations?

I have mainly worked with R410A and R32 on splits and multi-splits, plus R134a on chillers and some legacy R407C. R410A has a GWP of around 2,088, while R32 is about 675 and lower-GWP blends like R454B are around 466, so the industry is moving that way as the UK HFC phase-down reduces the quota available. Choice depends on capacity, safety and the building. R32 is classed A2L, mildly flammable, so charge limits, room size and leak mitigation under BS EN 378 and the manufacturer's instructions apply. R290, propane, is A3 and used on small sealed systems with strict charge limits. I always check the data plate, never mix refrigerants, use the correct recovery cylinder and gauges for the gas, and record every quantity handled in the equipment log, because F-gas compliance relies on that paperwork.

Common mistake to avoid: Treating all refrigerants as interchangeable; ignoring flammability classes

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Air Conditioning Engineer interview questions page. The first five are free, no sign-up needed.