ITI Refrigeration and Air Conditioning Viva Questions and Answers
In the refrigeration and AC practical, you braze or flare copper pipes, find a leak, vacuum and charge a system, or wire a compressor circuit, and the examiner then asks you to explain it. These are the questions asked most often, with short answers you can say in the viva.
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Your job first: neat, leak-free joints, correct vacuum and charge, correct wiring and a working system. Then your knowledge of the refrigeration cycle, refrigerants, tools, electrical parts and safety.
Refrigeration and AC viva questions with answers
The refrigeration cycle
Name the four main parts of the vapour compression cycle in order.
Compressor, condenser, expansion device and evaporator. The compressor raises the pressure of the vapour, the condenser rejects heat and turns it to liquid, the expansion device drops the pressure, and the evaporator absorbs heat from the space.
How to say it: Point to each part on the trainer or unit.
Which expansion devices are used?
A capillary tube in refrigerators, window and most split ACs, and a thermostatic or electronic expansion valve in bigger systems.
What is one ton of refrigeration?
About 3.5 kW (3.517 kW), or 12,000 BTU per hour of heat removed.
What is superheat and subcooling?
Superheat is how far the suction vapour is above its saturation temperature. Subcooling is how far the liquid leaving the condenser is below its saturation temperature.
What is COP?
Coefficient of performance: refrigerating effect divided by the work input. A higher COP means a more efficient system.
Refrigerants
Which refrigerants are used in a domestic refrigerator and an AC?
Refrigerators use R-134a or R-600a (isobutane). Older ACs used R-22; newer ACs use R-32 or R-410A.
Why is R-22 being phased out?
It is an HCFC that damages the ozone layer, so it is being phased out under the Montreal Protocol.
What extra care does R-600a or R-32 need?
Both are flammable, so work in a ventilated area, keep flames and sparks away and use tools rated for that refrigerant.
Tools and service
Why is a system evacuated with a vacuum pump before charging?
To remove air and moisture. Moisture can freeze in the capillary and choke it, and it forms acid with the oil.
How do you find a leak?
Pressurise the system with dry nitrogen and check joints with soap solution for bubbles, or use an electronic leak detector.
What is the difference between flaring and swaging?
Flaring opens the pipe end into a cone for a flare nut joint. Swaging expands the end so another pipe of the same size fits inside for brazing.
Which gas is used for brazing copper pipes?
An oxy-acetylene or LPG-air torch with a brazing rod; copper to copper can be brazed with a phosphorus-copper rod without flux.
What does the gauge manifold show?
The low side (suction) and high side (discharge) pressures, and it is used to evacuate and charge the system.
Electrical and safety
What are the relay and overload protector on a refrigerator compressor for?
The relay connects the starting winding for a moment at start. The overload protector cuts the supply if the compressor draws too much current or gets too hot.
What does the run capacitor do in an AC compressor?
It stays in circuit with the auxiliary winding and gives it a phase shift, so the PSC compressor motor starts and runs efficiently.
What safety do you follow during refrigeration work?
Goggles and gloves when handling refrigerant, ventilation, never braze a charged system, keep cylinders upright and away from heat, and switch off and discharge capacitors before touching wiring.
Your opening answer to practise
Copy the lines that are true for you, replace every [bracket] and delete the rest. Every number should be one you can repeat in a practical test.
Opening answer for the Refrigeration and Air Conditioning Technician viva
- My name is [name], roll number [number], trainee of ITI Refrigeration and Air Conditioning Technician, [ITI name], session [year].
- Today my practical job was [e.g. brazing a copper joint, pressure testing with nitrogen, then vacuum and charging a refrigerator].
- I followed the safety steps: [goggles and gloves worn, area ventilated, cylinder kept upright].
- The result: [e.g. no leak at the joints, system cooling with the correct suction pressure].
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Common questions
What questions are asked in the ITI refrigeration and AC viva?
The vapour compression cycle and its four parts, capillary and expansion valves, ton of refrigeration, superheat and subcooling, COP, refrigerants and why R-22 is phased out, vacuum, leak testing, flaring and swaging, brazing, gauge manifold, relay, overload and capacitors, and safety.
Which question is asked most often?
The refrigeration cycle in order, and why the system is evacuated before charging.
Is this the same as the AC technician interview?
The topics overlap, but the viva is about your practical job and the theory behind it. Our AC technician interview page covers questions a service company asks.
Can I get these viva questions as a PDF?
Open the page, choose Print in your browser menu, then Save as PDF. The page prints without menus.
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