A
filter system including a method for
self cleaning the
filter system of an
electronic equipment enclosure where air flow is monitored either by monitoring fan performance or air flow velocity through the
enclosure. The
system includes two filters elements, an upstream ASHRAE or
HEPA filter element to block particulate matter and a downstream PTFE
filter element to block
water vapor. The ASHRAE or
HEPA filter element is relatively inexpensive and easy to clean. The PTFE filter element is more expensive and difficult to clean. Thus, the cheaper filter is used to protect the more expensive filter from contaminants and to increase its useful life. The method of
self cleaning includes stopping the fan when a
signal is received indicating a predetermined resistance to air flow which is a function of blockage of the filter elements, thereafter operating the fan at an increased rotational velocity to determine whether the fan itself is malfunctioning, thereafter slowing and stopping the fan to allow the fan to be reversed, rotating the
fan in reverse for a predetermined period of time, such as five minutes, thereafter slowing and stopping the fan and returning the fan to its usual rotational velocity and direction. If the resistance to air flow is still above a predetermined level, the fan is again slowed, stopped and reversed and then returned to normal operation. The reversal operation can be conducted a multiple number of times, however, after a predetermined number, a
signal is sent requesting maintenance.