Cooling System and Airflow in an EX8208 Switch

The cooling system in an EX8208 switch consists of a single fan tray. The fan tray is a hot-insertable and hot-removable field-replaceable unit (FRU). The fan tray contains 12 fans.

The fan tray installs vertically on the left side on the front of the chassis and provides side-to-side chassis cooling. A handle on the front faceplate facilitates handling of the fan tray. See Figure 1.

Figure 1: Fan Tray for an EX8208 Switch

The fan tray can be removed and replaced from the front of the chassis. The switch continues to operate for a limited time (2 minutes) during the replacement of the fan tray without thermal shutdown.

Caution: You must replace the fan tray within 2 minutes of removing it.

The air intake to cool the chassis is located on the right side of the chassis. Air is pulled into the chassis and is pushed thorough the line card cage towards the fan tray. Hot air exhausts from the left side of the chassis. See Figure 2.

Figure 2: Airflow Through the EX8208 Switch Chassis

The Switch Fabric and Routing Engine (SRE) module monitors the temperature of switch components. Under normal operating conditions, the fans in the fan tray run at less than full speed. The fans are controlled by two fan tray controllers. The fans are numbered 1 through 12. Fans 1 through 6 are controlled by the first fan tray controller. Fans 7 through 12 are controlled by the second fan tray controller. If one fan tray controller fails, the other fan tray controller keeps half the fans working. This allows the switch to continue to operate normally as long as the remaining fans cool the chassis sufficiently.

If a fan fails or the ambient temperature rises above the threshold 113°F (45°C), the speed of the remaining fans is automatically adjusted to keep the temperature within the acceptable range, 32°F (0°C) through 104°F (40°C).

The fan tray continues to operate indefinitely and provide sufficient cooling even when a single fan fails provided the room temperature is within the operating range. You can check the status of fans and the chassis temperature from the Environment Status option in the Status menu on the LCD panel. See LCD Panel in an EX8200 Switch.

You cannot replace a single fan. If one or more fans fail, you must replace the entire fan tray.

Warning: There is no fan guard on the fans. Be careful to keep your fingers clear of moving fan blades when you are removing the fan tray.