2003 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or
stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2003-1
6
The top availability problem for survey respondents was airflow to IT equipment. Given the dramatic
increase in heat densities over the last few years, IT administrators are concerned that IT equipment will
suffer damage due to inadequate airflow. To make matters worse, there exists no standard of measuring
the cooling effectiveness of one rack enclosure over another. This is needed to insure a highly available
environment for critical equipment. One method of ensuring proper cooling is to specify a rack doors that
provide over 830 in
2
(0.53548 m
2
) of ventilation area or doors that have a perforation pattern that is at least
63% open. Rack doors meeting these specifications can provide sufficient "unassisted" airflow to ventilate
IT equipment. For poor cooling environments, supplemental air moving accessories are recommended for
racks over 1,500 watts. The subject of rack cooling is addressed in detail in the following APC White
Papers:
White Paper 41: "Rack Cooling options for Data Centers and Network Rooms"
White Paper 44: "Improving Rack Cooling Performance Using Blanking Panels"
White Paper 40: "Heat trends within Information Technology Rack Enclosures"
Survey respondents had negative experiences with rack based power strips that used unreliable circuit
breakers. These inexpensive types of circuit breakers represent a single point of failure that is often
overlooked. Furthermore, if they trip, it forces human intervention inside a rack filled with critical equipment.
This risk is further increased by the fact that someone now has to locate the circuit breaker somewhere on
the power strip. These issues are mitigated by locating circuit breakers on the same panel thereby
increasing the availability of critical racks. By far the best way to increase power availability at the rack is to
bring power redundancy to the rack. Respondents were surprised by the dramatic availability increase
when dual power sources are brought to the rack, even for single-corded IT equipment. This subject is
discussed in more detail in APC White Paper #125: "The Impact of Power Redundancy at the Rack".
