Electric defrost and hot-gas defrost cycles operate and what are practical differences?

• A. Electric defrost uses heating elements to melt frost; hot-gas defrost uses hot discharge gas to melt frost; Electric defrost is slower and energy-intensive; hot-gas defrost is faster but requires piping and controls to manage hot gas.
• B. Electric defrost uses hot discharge gas.
• C. Electric defrost requires no controls.
• D. Electric defrost uses cold air to remove frost

Answer: (A)

The point this question tests is how defrost methods actually melt frost and what that means in practice for a refrigeration system.

Electric defrost uses heating elements attached to the evaporator coils. When a defrost cycle starts, electricity heats those elements, warming the coils enough to melt the frost and drain the water. This method is simple and reliable, but because you’re heating frost with electric resistance, the process can be relatively slow and uses noticeable electrical energy during the defrost period.

Hot-gas defrost works by routing hot refrigerant gas discharged from the compressor back to the evaporator. The high-temperature gas transfers heat to the frost, melting it quickly. Because the heat comes from the refrigerant in the system, the cycle is typically much faster. However, it requires additional piping, valves, and controls to direct the hot gas and to integrate the defrost cycle with the normal cooling cycle, which adds complexity and cost.

So the practical differences come down to speed and complexity: hot-gas defrost is faster but requires more plumbing and controls; electric defrost is slower but simpler and uses electrical heating elements.