1. If either one of two AC power sources fails or is out-of-tolerance, the equipment must still be able to start up, or continue uninterrupted operation with no loss of data or reduction in hardware functionality, performance, capacity, or cooling.
2. After the return of either AC power source from a failed or out-of-tolerance condition during which acceptable power was continuously available from the other AC power source, the equipment will not require a powerdown, IPL, or human intervention to restore data, hardware functionality, performance, or capacity.
3. The first or second AC power source may fail one second after the return of the first or second AC power source from a lost or out-of-tolerance condition with no loss of data, hardware functionality, performance, capacity, or cooling.
4. The two AC power sources can be out of synchronization with each other having different voltages, frequencies, phase rotations, and phase angles as long as the power characteristics for each separate AC source remain within the range of the manufacturer’s published specifications and tolerances.
5. Both AC power inputs will terminate within the manufacturer’s equipment. Internal or external active input switching devices (e.g., static transfer switches) are not acceptable.
6. A fault inside the manufacturer’s equipment which results in the failure of one AC power source shall not be transferred to the second AC power source causing it to also fail.
7. An internal Uninterruptible Power System or internal power batteries (batteries for cache memory are acceptable) or other type of energy storage equivalent is allowable only for the purpose of a prompt orderly shutdown. The existence and volt-ampere capacity of an internal UPS or batteries and the time required for a prompt orderly shutdown must be identified.
8. With both AC power inputs available, the load on each power source will be shared within 10% of the average.
9. For three-phase power source configurations, the load on each phase will be within 10% of the average.
10. An external software alarm must be provided via the equipment’s software or the host’s operating system when an AC power source is lost or is outside the manufacturer’s published tolerances and when the abnormal condition is corrected.
11. The manufacturer will supply a written certification that the equipment meets or exceeds this specification for fault-tolerant power compliance.

Effective: November 1, 1998
© The Uptime Institute’s Site Uptime Network

This Fault-Tolerant Power Compliance Specification Version 1.1 has been established by the forty-five members of The Uptime Institute’s Site Uptime Network. The specification pertains to all computer and communication equipment critical to maintaining uninterrupted information availability.

Version 1.1 is current as of November 1,1998, and may be quoted or reproduced in its entirety at no charge. The version number must be included and copyright credit given to The Uptime Institute’s Site Uptime Network whenever the specification is quoted by reference or reproduced in its entirety.

Several updates to these specifications are expected during 1999 as user requirements become better defined and as hardware manufacturers determine what dual-power capabilities they can provide. For the most recent version, visit The Uptime Institute’s website at upsite.com, or contact the Institute by calling 505 986-3900. There is no fee for use of the specification or for obtaining updates.

Be warned that many products claiming to be dual-power compliant do not meet the specifications listed and will not offer the protection claimed or assured. The Uptime Institute intends to maintain a central registry of fault-tolerant power equipment which manufacturers have certified as being compliant as well as user comments (positive and negative) regarding their experiences with the equipment.