Oil-Free Magnetic Bearing Chillers Explained: Efficiency, Part Load and Maintenance for Data Centers November 9, 2026 By Paul Johnson, Technology & R&D, G&D Chillers Short answer: An oil-free magnetic bearing chiller uses a centrifugal compressor whose shaft floats on magnetic fields instead of oil-lubricated bearings, so there is no metal-to-metal contact and no oil system to maintain. For data centers, that means higher part-load efficiency, no efficiency loss from oil fouling over time, and less maintenance on equipment that runs 8,760 hours a year. This guide explains how the technology works, why it suits data center load profiles, and how it is used in G&D's GDX Series data center chillers. How does a magnetic bearing compressor work? A magnetic bearing compressor levitates its only moving part, the motor shaft and impeller assembly, on digitally controlled magnetic bearings. The most widely used design, the Danfoss Turbocor, uses one axial and two radial bearings, with sensors checking shaft position 100,000 times per second (Danfoss). Three other design features drive its efficiency: Variable speed drive built in. The compressor slows down to match load instead of cycling or throttling. Permanent magnet motor. Higher motor efficiency in a smaller, lighter package. Two-stage centrifugal compression. Efficient at full and part load, and suitable for both air-cooled and water-cooled chillers. The current Turbocor portfolio covers roughly 40 tons (140 kW) to 450 tons (1,600 kW) per compressor, and chillers combine multiple compressors for larger capacities (Danfoss portfolio, VTX1600 launch). Why are oil-free chillers more efficient at part load? Oil-free chillers are more efficient at part load because the compressor speed tracks the load continuously, and centrifugal compressor power falls sharply as speed drops. Data centers spend most of their life at part load because plants are sized for redundancy and future growth. Danfoss reports that Turbocor-based chillers can achieve integrated part load values (IPLV) up to 50% better than a comparably sized screw chiller (Danfoss). Actual savings depend on the chiller design, climate and operating profile. Load point Typical data center situation Why oil-free helps 100% Design day, all IT load online, one unit failed Comparable to other high-efficiency chillers 50% to 75% Normal operation with N+1 units sharing load Variable speed runs near peak efficiency 25% to 50% Early tenant ramp-up, cool weather, free cooling assist Largest advantage vs. fixed-speed and screw designs "A data center chiller plant with N+1 redundancy almost never runs a chiller at full load. That is exactly where magnetic bearing compressors earn their keep, and it's why we built the GDX Series around oil-free magnetic bearing technology." — Paul Johnson, Technology & R&D, G&D Chillers Do oil-free chillers lose efficiency over time? No. Because there is no oil in the refrigerant circuit, there is nothing to coat heat exchanger tubes and degrade heat transfer. An ASHRAE research project found oil content in older centrifugal chillers commonly above 4%, and Danfoss cites that a 4% oil content can cost about 9% efficiency (Danfoss). Danfoss also reports that its oil-free compressors held consistent performance after more than 10 years of operation (Danfoss). What maintenance does an oil-free magnetic bearing chiller need? An oil-free chiller eliminates oil changes, oil analysis, oil filters, oil heaters and oil pumps, and there are no mechanical bearings to wear. Routine maintenance focuses on coils, fans, water quality, electrical connections and controls. Maintenance task Oil-lubricated centrifugal or screw Oil-free magnetic bearing Oil changes and oil analysis Required Not required Oil filter, heater and pump service Required Not required Bearing inspection or replacement Periodic Not required (no contact) Coil and fan cleaning (air-cooled) Required Required Water treatment and strainers Required Required Controls and firmware updates Required Required Our technicians' guide to what actually fails first covers the components worth watching on any chiller. What are the best oil-free magnetic bearing chillers for data centers? The best oil-free chillers for data centers combine a proven magnetic bearing compressor with data center-specific features: high ambient capability, low-GWP refrigerant options such as R-1234ze and R-513A, and redundancy-friendly controls. Look for these specifications when you compare models: Certified part-load efficiency (IPLV or NPLV), not only full-load kW/ton Full capacity at your design ambient temperature Chilled water supply range that covers elevated setpoints for liquid cooling Refrigerant choices that meet EPA Technology Transitions limits Factory run-testing before shipment Local service and parts support Model Compressor Capacity Key feature Refrigerants GDX Air Danfoss Turbocor 250 to 2,000 kW Full load at up to 45 °C (113 °F) ambient, IP54, fits 20 ft or 40 ft high cube containers R-134a, R-1234ze, R-513A, R-515B GDX Free (GDX-Cool) Danfoss Turbocor 250 to 2,000 kW Integrated free cooling coils R-134a, R-1234ze, R-513A, R-515B What are the downsides of oil-free chillers? The main trade-offs are higher first cost and a dependency on power electronics. Oil-free chillers typically cost more upfront than screw chillers of the same capacity, and the drive and bearing controls need clean power and qualified technicians. For data centers running continuously, the energy and maintenance savings usually outweigh the higher purchase price. Our cooling cost guide walks through the lifecycle math. Frequently asked questions What is an oil-free chiller? An oil-free chiller uses a compressor that needs no lubricating oil, most commonly a centrifugal compressor with magnetic bearings. It removes oil systems from the chiller entirely. Is Turbocor a chiller brand? No. Danfoss Turbocor is a compressor. Chiller manufacturers, including G&D Chillers, build complete chillers around Turbocor compressors. How long do magnetic bearing compressors last? With no bearing contact, there are no wear surfaces in the compressor itself. Danfoss reports consistent performance after more than 10 years in service. Are oil-free chillers quieter? Yes. Turbocor TG compressors are rated as low as 70 dBA sound pressure, quieter than typical screw compressors (Danfoss). Can oil-free chillers use low-GWP refrigerants? Yes. Turbocor compressors are available for R-1234ze and R-515B, and G&D's GDX Series offers R-1234ze, R-513A and R-515B alongside R-134a. Compare oil-free options for your site. Explore the GDX Series or talk to a G&D application engineer.