I’ve culled these data center related questions from search engine traffic to the blog this week.
The first question is about 277VAC power. 277VAC is the low voltage component of 480Y277 (hot to neutral). 277 is used to provide lighting in industrial plants that generally use 480 3 phase power. Since most data center equipment universal power supplies top out at 250VAC, 277 really isn’t useful for anything except lighting.
The second question is about using 12VDC as DC power in the data center, vs 48VDC. 12VDC would require substantially more current to provide the same energy as 48VDC, meaning larger power plant, larger batteries, and larger conductors. Add to this that 12VDC is a non-standard voltage for this use and little to no data center equipment is going to support it. Unless you’re Facebook or Google and you can afford to have custom equipment made, stick to 48VDC.
The next question is what the best DC power plant batteries are. Rather than answer that, I’ll run down the criteria. Data center DC power plant batteries should be sealed (to prevent off gassing of flammable hydrogen), constructed to withstand possible deep discharge cycles without damage, and low sulfur content (to extend the battery life and prevent premature failure from sulfation). I usually use common sealed deep discharge 120AH batteries in the strings.
The final question is server room separation distance from the electrical equipment. This is a timely question with recent catastrophic electrical failures in data centers. The only thing in data center electrical equipment that represents a significant threat is an oil filled transformer and those should NEVER be placed inside the facility due to the risk of sudden catastrophic failure. In general, the server equipment should be as close as possible to the power equipment to reduce power loss in the cables, especially if you’re running a 48VDC power plant to supply your servers.
Vern, SwiftWater Telecom