ITI/NCVT RAC Mechanic (AITT Theory) case studies
ITI/NCVT RAC Mechanic (AITT Theory) · Put your knowledge to work in context.
The ITI/NCVT RAC Mechanic (AITT Theory) is the All India Trade Test theory paper for candidates who have completed the Refrigeration and Air Conditioning Mechanic trade under the Craftsman Training Scheme. It is conducted by the National Council for Vocational Training (NCVT) and is one of the requirements for the National Trade Certificate. The ITI/NCVT RAC Mechanic (AITT Theory) case studies are 5 cases and about 3,207 words.
1High discharge pressure on a dairy walk-in cooler after a fan motor replacement
A 12 m³ walk-in cooler for dairy storage is set to 4 °C and uses R-404A with a 3 HP semi-hermetic condensing unit and a thermostatic expansion valve. On a 40 °C afternoon the compressor cuts out on the high-pressure switch after about 8 minutes and restarts only after manual reset.
746 words, about 4 min2Domestic refrigerator compressor trips overload after a generic PTC starter was fitted
A domestic frost-free refrigerator rated 230 V, 50 Hz, 1.1 A has stopped cooling. The interior lamp and condenser fan work.
536 words, about 3 min3New R-32 split unit with poor cooling, an oil stain and no evacuation
A newly installed 1.5 TR inverter split air conditioner uses R-32 and a 5 m interconnecting pipe with a 3 m vertical rise. The manufacturer’s factory charge covers 5 m, so the installer adds no refrigerant.
674 words, about 3 min4Iced evaporator and low-pressure cycling in a walk-in freezer after defrost time was shortened
A 20 m³ walk-in freezer holding ice cream at -18 °C uses a 5 HP semi-hermetic R-404A condensing unit, electric defrost heaters, and a low-pressure switch set at 0.2 bar cut-out and 1.2 bar cut-in. Overnight the product rose to -8 °C and the evaporator is completely encased in ice; the fan blades are rubbing the ice.
566 words, about 3 min5Customer requests an R-407C drop-in retrofit of an R-22 packaged air conditioner
An old 5 TR packaged air conditioner serving a small office is charged with 3.2 kg of R-22 and uses mineral oil with a thermostatic expansion valve. The unit has a small leak at an evaporator flare and has needed top-ups twice this year.
685 words, about 3 min