Members of the ISP-Colo list share advice and warnings about designing or implementing your own Uninterruptable Power Supply (UPS).

[January 31, 2002]

On the ISP-Colo list in January, JB inquired,

"We haven't yet invested in a huge UPS for our data center; we're just using small Smart UPSes until we get big enough to need a larger one-what should I do to handle power outages?"

There was some disagreement as to whether or not Home Depot could provide the solution:

[AR advised] "Roll over to Home Depot and invest in a gas generator of the $300 Coleman variety."

[AP countered] "It's going to cost far more than $300 to get the generator in the basement wired to your room—assuming your landlord will even let you put a generator in the basement."

[EK offered] "It shouldn't cost much to have a portable generator hooked up to your power panel just in case. The landlord shouldn't have an issue with separating out your power feed if you pay for the work. The generator can be just about anywhere: basement, roof, parking lot—as long as the cable can reach."

Others warned that portable generators and data centers just don't mix:

[RL observed] "Portable generators aren't a good solution; they lack good voltage and frequency regulation."

[EK added] "It is possible to burn out a UPS with bad generator power. If the generator cannot maintain a stable load, then the fluctuations in the power can cause any UPS to burn out and shut down the power. Or even worse, it could flip to bypass and send the bad power to your delicate electronics."

[JM agreed] "I have tried in the past to run a generator behind a UPS. Your basic gas-powered generator will not work. Not only are the power fluctuations too much, but if the battery on your UPS is already dead, the generator will not power it at all."

Still others offered alternate suggestions:

[RL advised] "My recommendation would be to contact the power quality department at your utility. They should have figures about outages in your area. Figure out what the mean, median, and mode of the dataset are, and compare it your uptime requirements. Most of our POPs have two hours of battery backup, because 95 percent of the outages in that area are less than two hours."

[NL noted] "We use APC's Automatic Transfer Switch in client locations that need redundant power to a router, switch, or small server. We run one power feed with a UPS, and leave the second one empty. In the event of a longer power loss, we plug a small gas generator (one that's designed to feed electronics) into the second feed on the APC switch, fire the generator up and allow it to warm up for a few minutes-only then do we tell the switch to move from power source 'a' to power source 'b' and run on the generator."

—End