The TN11LOM Board Intermittently Reports the TEMP_OVER Alarm

The TN11LOM board intermittently reports the TEMP_OVER alarm due to the defective threshold crossing mechanism of the ambient temperature.

Product

OptiX OSN 6800

OptiX OSN 8800

Fault Type

Optical Transponder Unit

TEMP_OVER

Symptom

Certain TN11LOM boards in the OptiX OSN 6800 V100R003C02B01e equipment intermittently report the TEMP_OVER alarm. The ambient temperature in the telecommunications room, however, is within the normal range.

An equipment environment test conducted by the test engineers shows that the maximum operating temperature of the OptiX OSN 6800 subrack is 47.5°C and the minimum operating temperature of the subrack is 40.3°C when the ambient temperature is 26°C. The three TN11LOM boards in the subrack consecutively report the TEMP_OVER alarm. Query the performance statistics of the equipment. The query result shows that the operating temperatures of the three boards exceed 65°C. About three minutes later, the alarm is cleared. The alarm, however, is reported again two minutes after it is cleared. If you manually set the fan speed of the subrack to a level higher than the current level, the alarm is permanently cleared.

Cause Analysis

The SCC board in the subrack automatically adjusts the fan speed of the subrack according to the operating temperature of the SCC board. When the operating temperature exceeds 47°C, the fan speed is automatically adjusted to the high-speed level.

If a board other than the SCC board in the equipment reports the TEMP_OVER alarm, the fan speed is also automatically adjusted. In this case, the fan speed is automatically adjusted on a stepping basis.

The TN11LOM board detects its operating temperature every 250 ms. When the operating temperature of the board exceeds 65°C, the board reports the TEMP_OVER alarm.

When the operating temperature of the TN11LOM board exceeds 65°C, the board reports the TEMP_OVER alarm though the operating temperature of the SCC board is lower than 47°C. Therefore, the fan speed is automatically stepped up to lower the operating temperature of the equipment. About two minutes later, the operating temperature of the TN11LOM board is lower than 65°C and the TEMP_OVER alarm is cleared. At the same time, the SCC board detects its own operating temperature and finds that the temperature is lower than 47°C. In this case, the SCC board stops stepping up the fan speed and resumes the normal fan speed. Soon afterwards, the operating temperature of the TN11LOM board exceeds 65°C and thus the board reports the TEMP_OVER alarm again. In conclusion, the root cause of the problem that the TN11LOM board intermittently reports the TEMP_OVER alarm lies in the threshold crossing mechanism of the ambient temperature.

Procedure

1. Set the upper threshold of the operating temperature of the TN11LOM board to 70°C on the T2000. Then, the alarm is cleared. The TEMP_OVER alarm can be cleared in this way but the running life-span of the equipment will be affected in the long term.
   1. In the NE Explorer, select a board and choose Configuration > Environment Monitor Configuration > Environment Monitor Interface from the Function Tree.
   2. Click the Temperature Attributes tab. In the Temperature Upper Threshold (DEG.C) field, set the value to 70.
   3. Click Apply.
2. Manually adjust the fan speed to boost the heat dissipation efficiency of the equipment.
   1. In the NE Explorer, select an NE and choose Configuration > Fan Attribute from the Function Tree.
   2. Set Fan Speed Mode to Adjustable Speed Mode and set Fan Speed Level to High Speed.
   3. Click Apply.
3. Do not install multiple TN11LOM boards next to each other, if possible. Install them in the slots in the middle partition of the subrack because the heat dissipation efficiency in the middle partition is higher than that in the other partitions of the subrack.
4. Pay special attention to the ambient temperature in the telecommunications room. Ensure that the ambient temperature is moderate.

Result

This problem is solved.

Reference Information

Another possible cause for the equipment to report the TEMP_OVER alarm is that the dust filter is dirty and affects heat dissipation. If the alarm is caused by this issue, clean or replace the dust filter as soon as possible. You are advised to clean the dust filter every week and replace it every 6 months.

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