IBM DS4700 manual Statement

replaceable units (CRUs) and do not require preventive maintenance. Use only the supported power supply and fan units for your specific storage subsystem.

Each power supply and fan unit has a built-in sensor that detects the following conditions:

vOver-voltage

vOver-current

vOverheated power supply

If any of these conditions occurs, one or both power supplies will shut down. If the power remains off after the condition that causes it to go off, make sure that the environment is optimal (no overheating has occurred, all electrical outlets are working, and so on). For more information, see “Restoring power after an unexpected shutdown” on page 137.

The storage subsystem cooling system consists of two fans in each of the two power supply and fan unit CRUs. The power supply and fan units circulate air from the front to the back of the unit.

If both power supply and fan units fail, or if the power supply and fan units cannot maintain an internal temperature below 68° C (154° F), the power supply and fan units in the unit will automatically shut down (an over-temperature condition). If this occurs, you must cool the unit and restart it. See “Restoring power after an unexpected shutdown” on page 137.

Attention: The fans in the power supply and fan units draw in fresh air and force out hot air. The power supply and fan units are hot-swappable and redundant; however, if the fans in one power supply and fan unit fail, you must replace the entire failed power supply and fan unit within 72 hours to maintain redundancy and optimum cooling. Do not remove the failed power supply and fan unit until you have the replacement power supply and fan unit. When you do remove the failed power supply and fan unit, be sure to install the second power supply and fan unit within 10 minutes to prevent any overheating due to the interruption to the air flow that cools the storage subsystem.

Do not run the storage subsystem without adequate ventilation and cooling, because it might cause damage to the internal components and circuitry.

Use the following procedure to replace an ac power supply and fan unit. Figure 114 on page 168 illustrates removing and inserting a unit.

Attention: Potential damage to a component - To prevent damage from overheating, replace a failed power supply and fan unit CRU within 15 minutes of removal. If replacing it will take longer than 15 minutes, stop all I/O activity to the storage subsystem and turn off the power until you complete the replacement.

Statement 8:

Chapter 5. Replacing components 165