OSN6800V1R3C02B01e, part of the LOM cards reported TEMP_OVER alarm interruptedly. But the environment of the machine rooms is in the normal level.
Then we made an experiment in the Lab. At the ambient temperature reached 26 degrees, the top of the sub rack’s temperature was 47.5 degrees, the bottom was 40.3 degrees, three LOM cards in the sub rack reported TEMP_OVER alarm continuously. Query the performance, all three cards temperature around 65 degrees. About 3 minutes later, the alarm has disappeared. But just about two minutes, the alarm reproduced until setting fan speed to high level manually.
TEMP_OVER, the status LED in the card turns to red.
Change the upper threshold temperature of the LOM card to 70. The alarm disappeared.
The SCC card automatically adjusts the speed of the fan by investigating the ambient temperature. When the temperature is high than 47 degrees, the fan speed will be adjusted to “high”.
Another factor of automatically adjusting the fan speed is that whether there is the TEMP_OVER alarm reported by other cards. When it received the TEMP_OVER alarm from other cards, it will automatically speed up the fan by stepping.
The TN11LOM card investigates the ambient temperature interval period of 250ms. When the card detected the temperature is above 65 degrees, it will report the TEMP_OVER alarm.
When the temperature of the LOM increased to 65 degrees, the card reported the TEMP_OVER alarm. At this time the SCC hasn’t reached 47 degrees, but the SCC received the TEMP_OVER alarm from LOM card. It would speed up the fan to cool the system. After about 2 minutes, the LOM card temperature decreased lower than 65 degrees and the TEMP_OVER alarm disappeared. And the SCC investigated that itself temperature hasn’t reached 47 degrees. It would stop to speed up the fan and slow down it to the normal speed. After a while, the LOM’s temperature reached to 65 degrees again, the same phenomenon recurred again. It caused the LOM cards reported TEMP_OVER alarm interruptedly.
1, Change the upper threshold temperature of the LOM card to 70.
2, For the alarm (TEMP_OVER), we can manually set the fan speed to high to improve its cooling effect to the system.
3, If possible, please don’t put the LOM cards together. It recommended that the LOM card can be placed in the middle slots of the sub rack, or put it in the sub rack that there only lower power consume in the below sub rack. Because that the cooling fan is superior to the middle slots.
4, Or appropriate to lower the temperature of the machine room.