assive ventilation has its limitations. The flow of air into the cabinet is brought about by naturally occurring air turbulence in the room, so the cooling effect is dependent on activity in the room, air conditioning, open doors and windows, etc. You may need cool air to flow the most while you are watching a movie in your home theater, but a setting where the door is closed and everybody is sitting still is not very conducive to passive ventilation.

Staying below the maximum

Also, passive ventilation is less effective the higher the ambient temperature of the surrounding room is.

The maximum operating temperature your component system can tolerate is an absolute value; it is not relative to the room temperature. We recommend keeping your system operating at or below 85^o F. So if the temperature of the surrounding room is 70^o F, the system has an allowable heat increase of 15^o F. If the room temperature is 80^o F, the allowable increase is only 5^o F. Passive ventilation in the latter case will not cool the system sufficiently, unless the heat output is very limited.

To achieve more efficient cooling you need to increase the rate of heat transfer out of the system. The most cost-effective way is to increase airflow by adding fans. Fans propel air through the system at a much higher rate than natural convection. The amount of cooling air that flows through a system determines how much the temperature is allowed to rise due to heat generated by the components. The more air that flows through the cabinet, the less the temperature rises.

Exhaust and intake fans

Fans can be used either at the exhaust to “pull” warm air out of the cabinet or at the intake to push cool air in. Remember that natural convection creates an upward flow of warm air. This air will concentrate at the top of the cabinet if it cannot escape fast enough, creating a pocket of hot air. The most important use of fans is to help remove this warm air from your system. The exhaust fan should be placed at the top of the cabinet, at the end of the natural path of the warm air stream.

An intake fan at the bottom of the cabinet creates a stronger flow of cool air into the system. This helps transport warm air away from the components faster. It also increases the air turbulence inside the cabinet, which helps move warm air away from nooks where it might otherwise get trapped. And the added flow of air into the cabinet increases the internal air pressure, which helps prevent dust and dirt from entering.

For the optimal cooling effect we recommend using both intake and exhaust fans. These two sets of fans will supplement each other and create a strong, consistent airflow through the cabinet.

Advantages of fans

• Fans propel air through a component system at a high rate
• They are cost-effective
• They can be used at the exhaust to “pull” warm air out
• They can be used at the intake to “push” cool air in
• Intake fans help keep dust and dirt out