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Makers of fuel cells, which would replace generators, are just beginning to test marketplace, as well. Fuel cell installations promise to be simpler, as there are no noise or pollution issues and units are fairly compact. But costs are unclear.
Data center personnel also worry about maintaining and testing. “Very few companies want to schedule a test once a month or once a week. I don’t think they exist. I never heard of one,” says McHugh. For average small to medium-sized enterprise, weekly tests are probably unnecessary. However, larger companies may need to test more often.
“In a hospital or nursing home, JCHA [Joint Commission on Hospital Accreditation] recommends testing emergency generators once a week. They have to test under load and keep maintenance logs. How important is your data?” says Dauffenbach.
The best test is to use “building mode.” You simply simulate a power outage by cutting off power from outside. “Data centers don’t like to do that,” says Dauffenbach.
A compromise: Use a transition transfer switch. To test, or if you think an outage is coming, turn generator on first, synchronize generator’s output with utility’s power, and then open switch to cut off utility supply.
A more common approach is simply to turn on generator once a week or once a month, while utility continues to provide power to data center. Testing generator that way, without connecting to an external load (the equipment in data center itself), puts extra strain on it. Generator vendors recommend simulating load by installing a “dummy” load bank. The power can be dissipated with resistive wire (“Think of it as a giant toaster,” says Dauffenbach) or with inductive or capacitative loads. A 10KW load bank can cost $4,000 or more, depending on its type and its adjustability.
APC offers an annual service itself or through business partners worldwide. Under service plan, you can contract to have a test under load done periodically. The APC technicians arrive with their own load bank. “We also recommend testing under real load. Maybe quarterly, on a Sunday, shut down all noncritical processing tasks, check UPS batteries, and pull plug,” says Hunt.
The emergency generator business is dominated by local firms, working with local design consultants and electrical contractors. Among those suppliers who distribute nationally in addition to APC are Detroit Diesel, John Deere, and Caterpiller. You’ll be referred to a dealer-distributor such as Bowers Power, Covington Detroit Diesel-Allison, and GoPower.com.
Figuring The Size
Estimating generator size you might need involves more than adding up data center’s computer demand. Should you include power for air conditioning? “If you plan being on generator for no more than 20 or 30 minutes, you may not need air conditioning,” says McHugh. “But after 30 minutes, our preference is that at least a portion is put onto generator. A handful of lights is enough.”
If you include air conditioning, you will have to add extra generating capacity to allow for transient loads. Air conditioners, fans, and similar equipment start under load and draw far more than their rated power needs for a few seconds.
How to sell it to boss? “It comes down to dollars for everybody,” says McHugh. “What does this cost your company if you have a two-hour outage and you have a half-hour battery? Is this cost in hundreds of thousands? Millions?”