The following is a transcript of a webinar hosted by CAREL on 30 January 2024. This is part four of a four-part transcript.
Several studies, including ones conducted by laboratories, have demonstrated the benefits of electronic expansion valves over thermostatic valves.Image Credit: Freepik
Heat pumps are becoming increasingly popular in the HVAC industry due to their efficiency and versatility. In this webinar two experts delved into the intricacies of heat pumps, shedding light on key trends and regulations shaping the market:
- Miriam Solana Ciprés from CAREL’s Knowledge Center, responsible for following regulations and trends in HVAC
- Matteo Galenda, application specialist HVAC Residential
Next, we have a question related to the expansion valve. The question asks whether using an electronic expansion valve instead of a thermostatic valve influences compressor consumption. This question originated from Italy. Here, we have a table representing the comparison between the two types of valves. The main difference lies in the fact that the thermostatic valve is a mechanical device that operates using a bulb connected to the outlet to ensure correct function. On the other hand, a standard electronic expansion valve is controlled based on electrical signals from the controller, which then act on the stator. The stator, usually a stepper motor, changes the position of the internal device.
Here are the benefits of using the electronic expansion valve. Firstly, it ensures precise and stable superheat control, with faster regulation and a wide working range, making it ideal for DC compressors. This answers the question as it allows for accurate charging of the refrigerant, eliminating the need for frequent recalibration required for thermostatic valves. Another advantage is the perfect closure of the orifice, minimising the risk of liquid entering the compressor. In case of unit shutdown, the valve blocks the refrigerant, ensuring proper compressor restart. Additionally, in case of malfunction, the system can send an alarm to the controller, alerting the customer.
Several studies, including ones conducted by laboratories, have demonstrated the benefits of electronic expansion valves over thermostatic valves. Laboratory tests have shown a 50% reduction in power consumption during off cycles, attributed to faster attainment of setpoints and quicker valve closure. On-site testing revealed savings ranging from 15% to 35%, depending on operating conditions, with some studies reporting even higher benefits, up to 40%. In summary, using electronic expansion valves guarantees better performance and energy efficiency.
The next question pertains to sizing methodologies for heat pumps compared to boilers. Heating systems must compensate for losses in building transmission and ventilation to ensure comfort throughout the year. However, the methodologies differ between boilers and heat pumps. Boilers typically handle instantaneous hot water production, requiring higher thermal power compared to heat pumps, which often utilise a domestic hot water tank. Sizing for heat pumps considers factors such as geographical location and internal distribution temperature to achieve the right balance between heating demand and capacity.
The final question, from Germany, concerns key market trends. Detailed information can be found in our white paper, but to summarise, digitalisation is a significant trend, with demand response strategies and optimisation of components playing crucial roles. Heat pumps are being researched for expanded temperature ranges, compatibility with alternative refrigerants, and integration into ventilation systems. Other trends include noise reduction, smaller sizes and recyclability in line with circular economy policies and green objectives.
