HP Onboard Administrator - Manual (Page 265)

Configuring the HP BladeSystem c7000 enclosure and enclosure devices 265
Four Fan Rule
Fan bays 4, 5, 9, and 10 are used to support a maximum of two devices located in device bays 1, 2, 9, or
10. Note that only two of the device bays can be used with four fans.
Six Fan Rule
Fan bays 3, 4, 5, 8, 9, and 10 are used to support a maximum of eight devices in device bays 1, 2, 3, 4,
9, 10, 11, or 12.
Eight Fan Rule
Fan bays 1, 2, 4, 5, 6, 7, 9, and 10 are used to support a maximum of 16 devices in the device bays.