Recovering from an overheated power supply

A storage enclosure contains two power supplies. Each power supply contains a built-in temperature sensor to prevent the power supply from overheating. Under normal operating conditions, with an ambient air temperature range of 10°C to 40°C (50°F to 104°F), the fans in the power supplies maintain a suitable operating temperature inside the storage enclosure.

If the internal temperature reaches 65°C (149°F), the power supply shuts down automatically. If both power supplies shut down because of overheating, the storage enclosure has no power, and all LEDs are off.

The following factors can cause a power supply to overheat:

• An unusually high room temperature
• Fan failure in the power supply
• Defective circuitry in the power supply
• Blocked air vents
• Failures in other devices in the configuration or rack.

If a fan failure causes overheating, the system-error LED and overtemperature LEDs on the front bezel are lit. The fault LED on the power supply might also be lit. Checking the LEDs shows the locations of the LEDs on a storage enclosure.

To resume normal operation after a power-supply shutdown, complete the following steps:

1. Confirm whether you used the procedure in Solving problems to ensure that the power supplies have shut down because of an overheating problem.
2. Stop I/O activity to the storage enclosure.
3. Take all or some of the following measures to alleviate the overheating problem:
   • Remove all panels from the rack immediately.
   • Use external fans to cool the area.
   • Shut down the power to the storage enclosures, using the procedure that is described in Performing an emergency shutdown.
4. Wait for the air in and around the storage enclosure to cool. After the temperature inside the power supplies drops to below 65°C (149°F), the storage enclosure is capable of power-on recovery without operator intervention.

   If the power supplies do not restart automatically after the air has cooled, turn off both power switches on the storage enclosure (see Figure 1).

5. Turn on both power switches on the rear of the storage enclosure. The storage enclosure can take up to 10 minutes to power on and up to 15 minutes for the battery self-test to be completed. During this time, the LEDs on the front and the back of the storage enclosure flash intermittently.
6. Check the LEDs on the front and back of the storage enclosure (a green LED indicates a normal status; a yellow LED indicates a hardware fault).
7. If any module (power supply or ESM) does not display a green status LED, or if the status for any module component is not Optimal, diagnose and correct the fault.
   1. If you need to replace a failed component, locate and troubleshoot that component. See Checking the LEDs.
   2. If the problem persists, contact your IBM® technical-support representative.
8. Replace the bezel on the GSS, if applicable.