Answer
Work from the thermal output IBM publishes for the machine type, then divide by 12,000 BTU per hour, which is one ton of refrigeration.
Maximum thermal output by machine type:
- Power S1112 (9242-21B): 1,877 BTU/hr, about 0.16 tons
- Power S914 (9009-41A): 5,461 BTU/hr, about 0.46 tons
- Power S922 (9009-22A): 6,416 BTU/hr, about 0.53 tons
- Power S924 (9009-42A): 9,386 BTU/hr, about 0.78 tons
- Power S1024 (9105-42A): 9,383 BTU/hr, about 0.78 tons
- Power S1124 (9824-42A): 10,065 BTU/hr, about 0.84 tons
- Power E950 (9040-MR9): 14,403 BTU/hr, about 1.2 tons
- Power E1080 node (9080-HEX): 15,355 BTU/hr, about 1.28 tons
- Power E1050 (9043-MRX): 16,889 BTU/hr, about 1.41 tons
- Power E1180 node (9080-HEU): 16,548 BTU/hr, about 1.38 tons
- Power E1150 (9043-MRU): 18,245 BTU/hr, about 1.52 tons
A single 4U scale-out machine is most of a ton on its own. Four of them in a rack is a three to three and a half ton problem before storage, networking, or the HMC are counted, and a four-node enterprise system runs to five and a half tons.
These are rated ceilings rather than steady-state loads, so a room built entirely to them will be over-provisioned. They are the right basis for the worst case, and the measured figures are the right basis for the day-to-day one.