Antminer S21 owner hub: exact air, hydro and immersion references

Owner-first S21 reference hub: identify the complete printed model name, every suffix, cooling class, input topology, rated mode, control board, and installed firmware before selecting specifications, parts, firmware, or recovery instructions.

Similar S21 names are separate hardware identities. Do not transfer a PSU, hashboard, controller, image, recovery medium, coolant or oil requirement, tune, or facility design between cards.

Air-cooled canonical references

Hydro canonical references

Facility gate: these are industrial liquid-cooled, three-phase systems. Exact input, fluid, flow, pressure, inlet temperature, connector, water quality, and heat rejection are model-specific.

Immersion canonical reference

Full-immersion gate: this machine must operate fully immersed in a validated dielectric-oil system; it is neither an air-cooled nor a hydro-loop server.

Names currently withheld from the canonical directory

S21+, S21+ Hyd., S21 XP+ Hyd., S21 XP Imm., S21e Hyd., and S21e XP Hyd. are OEM-confirmed names, but the standalone specifications previously published on this site are not included here without durable exact-model manufacturer evidence. Their identity pages remain outside this canonical ItemList until the evidence is sufficient.

Identify before firmware or recovery

The reviewed manufacturer board-selection matrix does not list S21 models. A family name cannot select a controller category, firmware package, recovery medium, or lock procedure.

1. Identify the exact board and collect the installed version.
2. Match the complete suffix, cooling system, electrical topology, and current exact manufacturer support entry.
3. For no boot, conflicting identity, interrupted updates, fluid exposure, coolant alarms, instability, or electrical and thermal symptoms, request diagnosis before recovery.

Evidence and commerce policy

Each canonical profile separates manufacturer ratings from unknowns and cites primary sources. Retail inventory remains on separate product pages. Reference pages and this hub use ProductModel schema without offers; duplicate and evidence-limited pages are excluded from the canonical ItemList and sitemap.