CloudEngine Series Switches FAQs-3.3 Fan Module

CE12804/CE12808/CE12812/CE12816/CE12804S/CE12808S

NOTE:

• The CE12804/CE12808/CE12812/CE12816 chassis use the same heat dissipation mode. The CE12812 chassis is used as an example here.
• The CE12804S/CE12808S chassis use the same heat dissipation mode. The CE12808S chassis is used as an example here.
• If a CE12800 chassis is not fully loaded with cards, cover vacant slots with filler panels to ensure efficient heat dissipation and EMC compliance.

Figure 3-25 shows the airflow for heat dissipation of SFUs and power modules in a CE12812 chassis.

• Cold air flows into the chassis from the air intake between the LPU cage and power modules and reaches the bottom of the SFU cage. After cold air flows upwards through the SFU cage, it turns into hot air and is exhausted from the chassis by the fan modules above SFUs.
• Cold air flows into the power modules from air holes on power module panels and is blown through the power module area by built-in fans of the power modules. Cold air then becomes hot air, passes through the backplane, and goes out of the chassis from air holes on the power distribution unit.

Figure 3-25  Airflow for heat dissipation of SFUs and power modules (side view)

Figure 3-26 shows the airflow for heat dissipation of MPUs, CMUs, and LPUs in a CE12812 chassis. Cold air flows into the chassis through air holes on these cards, and goes through the cards to dissipate the heat. After that, cold air turns into hot air, bypasses the backplane, and is finally exhausted from the chassis by the fan modules at two sides of the SFUs.

Figure 3-26  Airflow for heat dissipation of MPUs, CMUs, and LPUs (top view)

Figure 3-27 shows the airflow for heat dissipation of MPUs, SFUs, LPUs, and power modules in a CE12808S chassis.

• Cold air flows into the chassis through air holes on panels of the MPUs, SFUs, LPUs, and goes through these cards to dissipate the heat. After that, cold air turns into hot air, goes through the backplane, and is finally exhausted from the chassis by the fan modules at the rear of the chassis.
• Cold air flows into the power modules from air holes on power module panels and is blown through the power module area by built-in fans of the power modules. Cold air then becomes hot air, passes through the backplane, and goes out of the chassis from air holes on the power distribution unit.

Figure 3-27  Airflow for heat dissipation of MPUs, SFUs, LPUs, and power modules (side view)

CE12804E/CE12808E/CE12816E

NOTE:

• The CE12804E has heat dissipation mode than other chassis.
• The CE12808E/CE12816E chassis use the same heat dissipation mode. The CE12808E chassis is used as an example here.
• If a CE12800 chassis is not fully loaded with cards, cover vacant slots with filler panels to ensure efficient heat dissipation and EMC compliance.

The SFUs in the CE12804E chassis are cooled in the following way:

1. Cold air flows into the chassis from the SFU air intake vents below the chassis header at the front of the chassis, and then arrives at the top of the SFUs.
2. Cold air goes down through the SFU cage and becomes hot air, which is exhausted out of the chassis by the two fan modules at the bottom left and bottom right.

Figure 3-28 shows the airflow for heat dissipation of SFUs.

Figure 3-28  Airflow for heat dissipation of the SFUs (side view)

The MPUs and LPUs in the CE12804E chassis are cooled in the following way:

1. Front panels of the MPUs and LPUs have air holes. Cold air flows from these air holes to the MPUs and LPUs.
2. Cold air turns into hot air and goes through two sides of the SFUs in the middle. Finally, hot air is exhausted from the chassis by the fan modules at both sides of the SFU cage.

Figure 3-29 shows the airflow for heat dissipation of the MPUs and LPUs.

Figure 3-29  Airflow for heat dissipation of the MPUs and LPUs (top view)

Power modules in the CE12804E chassis use a front-to-back airflow design.

1. There are air holes on power module panels. Cold air flows into the power modules from these holes and is exhausted from the power module area by fans of the power modules.
2. Hot air is exhausted out of the chassis from the power module air exhaust area at the rear lower part of the chassis.

Figure 3-30 shows the airflow for heat dissipation of power modules.

Figure 3-30  Airflow for heat dissipation of the power modules (side view)

The SFUs in the CE12808E chassis are cooled in the following way:

1. Cold air flows into the chassis from the SFU air intake vents below the chassis header at the front of the chassis, and then arrives at the top of the SFUs.
2. Cold air goes down through the SFU cage and becomes hot air, which is exhausted out of the chassis by the three fan modules below the SFUs.

Figure 3-31 shows the airflow for heat dissipation of SFUs.

Figure 3-31  Airflow for heat dissipation of the SFUs (side view)

The MPUs and LPUs in the CE12808E chassis are cooled in the following way:

1. Front panels of the MPUs and LPUs have air holes. Cold air flows from these air holes to the MPUs and LPUs.
2. Cold air turns into hot air and goes through two sides of the backplane in the middle. Finally, hot air is exhausted from the chassis by the fan modules at both sides of the SFU cage.

Figure 3-32 shows the airflow for heat dissipation of the MPUs and LPUs.

Figure 3-32  Airflow for heat dissipation of the MPUs and LPUs (top view)

Power modules in the CE12808E chassis use a front-to-back airflow design.

1. There are air holes on power module panels. Cold air flows into the power modules from these holes and is exhausted from the power module area by fans of the power modules.
2. Hot air is exhausted out of the chassis from the power module air exhaust area at the rear lower part of the chassis.

Figure 3-33 shows the airflow for heat dissipation of power modules.

Figure 3-33  Airflow for heat dissipation of the power modules (side view)

CE8800&7800&6800&5800

The CE8800&7800&6800&5800 series switches are cooled through front-to-back or back-to-front airflow, depending on the airflow directions of the fan modules and power modules used in the chassis. Each fan module and power module has an airflow flag.

• Front-to-back airflow: Power modules and fan modules with front-to-back airflow are identified by a or flag. Air flows into the chassis from the power supply side and is exhausted from the port side, as shown in Figure 3-34 (using a CE5800 chassis as an example).
• Back-to-front airflow: Power modules and fan modules with back-to-front airflow are identified by a or flag. Air flows into the chassis from the port side and is exhausted from the power supply side, as shown in Figure 3-35 (using a CE5800 chassis as an example).

NOTE:

• The CE5850EI and CE5810EI series switches support 1+1 redundancy of fan modules. A CE5850EI or CE5810EI switch can work normally with a single fan module, but the device reliability degrades in this case.
• The CE5850HI, CE5855EI, CE6800, and CE7800 switches have two power modules, each of which consists of two fans. The four fans in a switch work in 3+1 redundancy mode.

• Power modules using forced air cooling and fan modules in a switch must have the same airflow direction. For example, power modules with back-to-front airflow must be used with fan modules with back-to-front airflow.

• When a switch uses fanless 150 W AC power modules, it can use fan modules with either of the airflow directions based on the actual conditions.

Figure 3-34  Front-to-back airflow

Figure 3-35  Back-to-front airflow

Airflow of a switch cannot be changed through software, but you can determine the airflow by selecting specific power modules and fan modules.

NOTICE:

• Power modules with different airflow directions or power values cannot be used in the same switch.
• Fan modules with different airflow directions cannot be used in the same switch.
• An alarm will be generated if a switch does not use any power module and fan module combination listed in Table 3-17.

Table 3-17 lists the combinations of power modules and fan modules allowed by CE8800&7800&6800&5800 series switches.

CE12800

The following situations may cause full-speed running of fans in a CE12800 series switch:

1. The cards in a zone overheat, and fans in this zone must run at full speed to lower card temperature.
2. Some cards in a zone have all temperature sensors failed and card temperature cannot be obtained.
3. Management channels in a zone are interrupted, so the system cannot obtain card temperature in this zone.
4. The management channels of some fans are interrupted, so the speed of these fans cannot be adjusted based on real-time card temperature.
5. If any of the preceding situations occurs in a zone, fans in the adjacent zones with running cards also run at full speed.
6. No Centralized Monitoring Module (CMU) is installed in the switch or the CMUs in the switch have failed.
7. Fans also run at full speed when you set the fan speed to the highest using the set fan-speed command.

You can see alarm messages on the network management system in situations 1 to 5.

CE8800&7800&6800&5800

The following situations may cause full-speed running of fans in a CE8800&7800&6800&5800 series switch:

1. There is only one fan module in the switch. In this case, the switch generates fan module absence alarms for idle fan slots, and fans in the present fan module work at full speed.
2. Power modules and fan modules in the switch use different airflow designs. In this case, the system reports alarms about inconsistent airflow directions of the power modules and fan modules. Inconsistent airflow directions between power modules, fan modules, or between power modules and fan modules degrade system reliability when the switch needs to work in a high-temperature environment for a long time, and shorten service life of the switch.
3. The management channels of some fans are interrupted, so the speed of these fans cannot be adjusted based on real-time equipment temperature.
4. Fans also run at full speed when you set the fan speed to the highest using the set fan-speed command.

Possible Causes

• The fan module is not installed properly in the fan slot.
• Fan blades are blocked or stop rotating because of heavy dust.
• The fan module is faulty.

Troubleshooting Procedure

1. Pull out the fan module and reinstall it to ensure that it is securely installed in the slot. (Fan modules are hot swappable.)
2. Remove the fan module from the chassis and check whether the fan blades are blocked or whether there is too much dust on the fan blades.
   • If fan blades are blocked by an obstacle, remove the obstacle.
   • If the fan blades have heavy dust, use a brush to clean the fan blades.
3. If the problem persists, install another fan module of the same model into the fan slot. If the new fan module can work normally, the original fan module has failed and needs to be replaced.