Electrical Loads: How Should Data Center Systems be Protected?

We are routinely asked how various data center systems should be protected. Usually the customer wonders what systems should be protected by an uninterruptible power supply (UPS) and what loads should be placed on a backup generator.

In the average data center we find several critical systems: the enterprise itself, precision cooling, fire suppression, life safety, physical security, etc. All of these systems are critical to normal operations, but in the event of a power outage, how are these systems prioritized and how are they protected? The answer is relatively straight forward; the UPS should be dedicated to supporting the enterprise. Regardless of the facility’s operation strategy for power outages, (be it to achieve an orderly shut down of the enterprise or to operate the enterprise until the facility’s backup generator comes online) the UPS is present to provide short term, interim protection for enterprise hardware.

The reason for this prioritization is straight forward, the loads associated with the cooling plant, such as compressors, pumps and fans are so large as to make it impractical to support them on UPS power. In addition, most data centers can operate during a brief outage of the cooling plant. For these reasons cooling plant components can be protected by backup generator power without a requirement for UPS power.

As for fire protection systems, data center fire detection and suppression systems should be placed on the backup generator supplied emergency power circuits, but must also incorporate their own battery backup system. Typically a maintenance free battery and charging system is built into the facility fire panel. It is imperative that the battery be maintained and replaced per the manufacturer’s recommendations. Failure to do so could result in the system not activating when needed, or in some failure modes, causing an inadvertent discharge of the suppression system.

Likewise, key life safety systems, such as emergency lighting should be engineered to operate independently of the UPS. As with the fire protection systems, emergency lighting batteries must be maintained per manufacturer’s recommendations and be connected to generator supplied emergency power system.

Normal facility systems, such as lighting and comfort cooling outside of the data center, are somewhat of a mixed bag. Often normal data center lighting will be placed on backup generation to allow continued operations in the facility. Generally speaking comfort cooling is not a priority as it is not necessary for most data center operations.

Management may also wish to consider defining telephone equipment as mission critical and placing it on UPS power as well. This will ensure uninterrupted voice capability in the event of a power outage. While a power outage may curtail normal office operations, communications in and out of the building would be an essential service for data center personnel and any skeleton staff asked to occupy the building during an extended outage.

While on the subject of UPS and generator systems, deployment of a UPS and/or generator is only the first step in protecting a data center. A commitment to periodic testing and maintenance of these systems must be made by data center personnel and management. While UPS and generator systems are very robust, they are like any mechanical system and require ongoing maintenance to ensure they work properly when needed. UPS systems should be maintained by factory trained personnel at least once a year.

Back up generators should be tested at least once a month and allowed to run long enough to attain normal operating temperatures. Like UPS systems, generators should be inspected and serviced at least once a year by factory authorized technician,s to ensure the system is fully functional and available when it is needed. Generators also require a programmatic approach to ensure availability. Data center or facilities managers should ensure their generator has sufficient onsite fuel storage to run continuously for extended periods of time. Generally 24 hours of operation at full load is a good target to aim for. Also, management should have pre-existing contracts in place for re-fueling and be assured that their fuel vendor will be able to deliver fuel even in adverse conditions.

A few other items that should be kept in mind in regard to generators include maintaining basic spare parts onsite. Extra engine oil, serpentine belts, filters, hoses and basic tools will give you a fighting chance to make simple repairs if needed. One item that is often overlooked is the generator starting battery. Generator batteries should be float charged and tested periodically to ensure they are in excellent condition and able to start the generator when needed.

UPS and backup power systems are essential for reliable data center operation. Design and deployment of these systems is not difficult, but do require solid planning and a commitment to good maintenance and operational practices. A few dollars spent on system consulting from a qualified vendor will not only ease the system design and deployment process, but will also reduce the chance that your essential back up systems will fail when needed most.