Stacking Guidelines - Cisco GoQAM Installation And Operation Manual

Chapter 2 Installing the GoQAM

Stacking Guidelines

The GoQAM is a high-density, high performance device for digital broadband data
delivery. One GoQAM performs the services of two QAM modulators. This space-
saving feature makes the GoQAM the device of choice for contemporary digital
broadband delivery systems.
Providing proper ventilation and cooling for the modulator is mandatory. You can
stack up to 32 GoQAM devices in a standard 40-rack unit (RU) equipment rack if
you read and carefully follow the guidelines provided in this section and later in this
chapter.
Each GoQAM contains three dual fan packs that provide forced air cooling. These
fan packs, located on the side of the unit, pull air across the internal circuitry to
remove heat.
Important! In order for the fans to operate correctly, you must install each GoQAM
using the rack mount brackets included with the unit. These brackets contain
notched cutout sections to allow for clearance so that air can enter and leave the unit
without restriction.
When you install the GoQAM in the rack using the rack mounts provided, you can
install them directly above and below each other with no requirements for vented
spacers. Using these rack mounts also provides support for the modulator. The
GoQAM is not intended to be suspended or "hung" in the rack by only mounting the
front bezel support.
Controlling Operating Temperature
CAUTION:
Cisco headend equipment is designed to operate in a maximum 122°F (50°C)
environment. Specifically, this means that the air temperature at the air inlet
of any GoQAM must never exceed 122°F (50°C).
Each GoQAM draws up to 151 W of input power and a total of 515 BTU/hr. For a
full rack with 32 units, the sum total is 4832 W per rack, or 16,480 BTU/hr. You
should make your HVAC considerations based on these calculations.
Controlling Exhaust Air
Exhaust air management is the key to cooling multiple modulators in a custom rack
configuration. Inlet air temperature should be as cool as possible and should never
exceed 122°F (50°C). Exhaust air should have little or no restrictions. Obstructions
such as cabling or other devices that block airflow to the side or top of the rack
should be avoided.
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