Impact of Electrification on HVAC Compressor Refrigerants

In addition to regulatory shifts, electrification is a major trend in the HVAC industry, with a focus on electric motors, heat pump technologies, and inverters to reduce the overall carbon footprint of systems. There is great emphasis on efficiency, as the energy required to operate heating and cooling systems is now seen as a primary driver of global warming – more so than refrigerant emissions. The move to electrified systems is influencing refrigerant choices and system designs as manufacturers seek to balance environmental regulations, efficiency, and safety.

As compressor OEMs are required to design new systems or retrofit existing ones with these next-gen refrigerants, they need experts who understand refrigerant properties and their compatibility. Supplier partners with global resources and deep refrigerant knowledge can provide OEMs with the confidence to perform their own tests or collaborate on custom projects.

Selecting the Best Materials for Refrigerant Compatibility in HVAC Compressors

Refrigerant-compatible materials must have low swell properties, meaning the material does not significantly expand when immersed in refrigerant. They also need to exhibit low hardness and weight change to ensure chemical compatibility and long-term durability. Mechanical properties of the materials must be retained throughout the compressor’s operational life, given that many compressors are fully hermetic – completely sealed and not serviceable. As systems may operate in extreme environments, materials need strong performance at both low and high temperatures, from -22 °F to +302 °F / -30 °C to +150 °C, and in some cases, even higher. Low extractability is important to prevent material ingredients from being pulled out by the solvent effects of refrigerants, which could affect system efficiency and damage downstream components. In some cases, electrical resistivity is required, depending on the application.

After the challenge of identifying appropriate materials has been addressed, it is necessary to choose the right products and design. HVAC equipment uses a wide variety of elastomer components, including O-Rings, custom-molded elastomers, and damping and vibration elements. Trelleborg is uniquely positioned to partner with OEMs to select materials, perform testing, and design a complete sealing system for HVAC equipment.

Testing Elastomer Materials for Next-Generation HVAC Refrigerants

Trelleborg is investing in its own testing capabilities for HVAC compressor refrigerants. Experts followed modified ASHRAE specifications 97 and 38, which are used in testing HVAC compressor materials for immersion and extractability. They tested four ethylene propylene diene monomer (EPDM) rubbers, two hydrogenated acrylonitrile butadiene rubber (HNBR), and two chloroprene (CR) materials in both current and future refrigerants. Testing involved 14-day immersion of elastomer samples at temperature (+158 °F to +212 °F / +70 °C to +100 °C, depending on material), primarily in vaporized refrigerant, followed by tensile, swell, and hardness measurements before and after exposure. Experts performed extractability testing using acetone to determine what compounds could be pulled out of the elastomers, addressing concerns about downstream effects and system efficiency.

The results showed that a full elastomer portfolio is still needed for the next generation of refrigerants. Most of the materials tested exhibited strong chemical compatibility. The polyalkylene glycol (PAG) and polyol ester (POE) oils – which are common lubricants used in refrigeration systems—were often the limiting factor. Fluorinated refrigerants alone showed limited effect on Trelleborg’s EPDM, HNBR, and CR materials. When tested in PAG and POE oils, the swell effect was pronounced in several elastomers, especially EPDMs. When combined with the fluorinated refrigerant, the degradation effects were slightly reduced due to the lower concentration of oil. A particularly challenging combination arose when testing an HFO in combination with mineral oil at high temperatures. Natural refrigerants showed strong compatibility with the CR and HNBR elastomers tested. HVAC OEMs can work with Trelleborg material and testing teams when material compatibility is unknown or needs to be validated.

The Future of HVAC Compressor Design: Collaboration and Innovation

The evolution of compressor refrigerants in the HVAC industry showcases a commitment to addressing complex environmental, regulatory, and technological challenges. The focus on next-gen refrigerants that offer efficiency, low environmental impact, and safety demands collaboration and adaptable solutions. By prioritizing innovation and partnering with suppliers dedicated to testing refrigerant materials, compressor OEMs will be equipped to confidently design new systems or retrofit existing ones.

Common Types of HVAC Compressors: Screw, Scroll, Centrifugal, and Reciprocating

Four common types of compressors used in the HVAC industry are screw, scroll, centrifugal, and reciprocating.

• Screw: Uses two meshing helical screws (rotors) to compress gas as it moves through the chamber. Commonly seen in large HVAC systems, manufacturing, and industrial refrigeration settings. They boast long service life, high efficiency at full loads, and a continuous, smooth flow of compressed air.
• Scroll: Uses one stationary and one orbiting spiral scroll to compress refrigerant. It is commonly used for residential and light commercial HVAC systems because it is quiet and highly efficient, with few moving parts.
• Centrifugal: Uses a rotating impeller to add velocity to the refrigerant, which is then converted to pressure in a diffuser. Typical uses include large commercial buildings, chillers, and process cooling. It contains few moving parts and is ideal for steady, high-volume applications.
• Reciprocating: Uses a piston driven by a crankshaft to compress air or gas in a cylinder. Used for refrigeration, automotive air conditioning, and small industrial systems due to its high-pressure output, easy maintenance, and cost-effectiveness for small-scale applications.