What is the Accelsius MR250?
The MR250 is Accelsius's 250 kW in-row distribution and heat-rejection unit for several racks using the NeuCool two-phase direct-to-chip loop. Dielectric refrigerant boils at processor plates, carries heat as vapor, and is condensed and recirculated by the shared unit. The arrangement moves pumps and controls out of each rack and can reduce repeated hardware, but it also creates a shared operating boundary. Capacity must be allocated across all attached racks, and isolation matters when one rack or branch needs service. Accelsius supplied an MR250 for system-level testing in the United States Department of Energy's Advanced Research Projects Agency–Energy COOLERCHIPS program. The company also reported a full 250 kW rack demonstration with 40°C facility water, but that broader platform test should not be read as a complete MR250 acceptance test for every layout. The cited announcement planned general availability for late 2025; it does not provide current lead time or installed-base data. Public material does not disclose dimensions, refrigerant charge, facility connection sizes, pump curves, electrical input, sound, pressure limits, or capacity after a pump, power, or controller failure. Ask how many racks and plate branches the quoted duty assumes, which server configurations are approved, and how residual air heat is handled. Procurement should require duty-point data, refrigerant safety and recovery procedures, alarm and control interfaces, branch isolation, factory testing, commissioning scope, spares, and service coverage.