A newly installed cold climate heat pump is designed with a variable-speed compressor and an enhanced vapour injection (EVI) system. At an outdoor temperature of -15°C, what is the primary benefit of the EVI system compared to a conventional heat pump without this technology?

Question: A newly installed cold climate heat pump is designed with a variable-speed compressor and an enhanced vapour injection (EVI) system. At an outdoor temperature of -15°C, what is the primary benefit of the EVI system compared to a conventional heat pump without this technology?

Answer options: ✅ Significantly increased heating capacity and improved efficiency by injecting partially evaporated refrigerant into an intermediate stage of the compressor.

• Reduced electricity consumption by entirely bypassing the compressor at lower ambient temperatures.
• Elimination of the need for auxiliary heat by employing a secondary thermodynamic cycle.
• Faster defrost cycles by reversing the flow of refrigerant through the outdoor coil at a higher pressure.

Correct answer: Significantly increased heating capacity and improved efficiency by injecting partially evaporated refrigerant into an intermediate stage of the compressor.

Explanation: Enhanced Vapour Injection (EVI) technology, often found in cold climate heat pumps, significantly boosts heating capacity and efficiency in cold conditions by injecting saturated or superheated vapour into an intermediate port of the scroll compressor, thereby allowing higher compression ratios with improved efficiency.