Author: Dave Norwood
The United States is slowly seeing the benefits of 208-volt power over 110-volt. I didn’t truly understand the benefits until I ran into a problem with a large 4-processor Intel server. Turns out that this particular server with four power supplies, only needed two to run when fed 208-volt, but needed three power supplies when fed 110-volt. This became a problem when the client had dual power busses (sources/feeds) and one bus lost power. They had two power supplies plugged into one 110v power bus, and the other two power supplies in the other 110v bus. When one power bus/source died, only two power supplies had power, and they needed three power supplies to power the server at 110-volt. By simply jumping up to 208-volt we had true fault tolerance, only two power supplies needed to power the server. This really hit the efficiency and benefits of 208-volt power home for me. I’ve never looked back. I now recommend 208-volt in most cases.
What is the engineering behind this? Amps * Volts = Watts (less power factor). Thus, if you increase volts by going from 110v to 208v, you need less amps to feed your equipment the same number of watts (bring out your old algebra book). The loss due to the resistance of the wire is proportional to the amperage. With a lower voltage, you have to push more amps, which means more power is wasted as heat. Also, with fewer amps, you can use smaller wires without fear of starting a fire (overheat from overload). This saves money; there is less energy loss to heat and less copper to carry the power. These are some of the reasons why electric companies use very high voltages until they get close to your home/business.
So, what does it take to move to 208-volt in your datacenter? In many cases you just need to change out your rack PDU’s (aka power strips). If your UPS can supply 208v, you don’t even need to upgrade your UPS power source. In fact, many UPS units natively support 208-volt and you have to buy a step-down transformer to provide 110-volt. The step-down transformer adds cost and complexity. Finally, and most importantly, you need to confirm all of your equipment supports 208-volt. Most modern equipment is “auto switching” and can support anything from 100-volt to 250-volt. The power supply will be marked with this information. I’ve had the most problems with “power bricks” not supporting 208-volt. When that is the case, you can change out the power brick; however, I’m now seeing more and more power bricks that are auto-switching, which means you just need to switch out the power cord that feeds the brick. If this is your first time converting a datacenter, you might want to work with a knowledgeable partner like Trusted Network Solutions; we’ll help you avoid the many pitfalls.
During your conversion you will need to get familiar with IEC power outlets vs. NEMA. NEMA is what you are most familiar with. The power outlets in your home are NEMA 5-15 (3-prong 15amp). In your business you mostly likely have NEMA 5-15 and NEMA 5-20 (3-prong 20amp). NEMA 5-20 can be identified by the fact one of the “pins” is twisted by 90 degrees. When you go to 208-volt power, you will be switching to IEC power outlets. The two primary datacenter sets are IEC C13/C14 and IEC C19/C20. Check out this site for more information:
In addition to my comments above, this white paper from APC helps explain why 208v is better in many cases (but not all). Note: When you hear people say 208v versus 220v they are most likely talking about the same thing. In most cases related to this specific datacenter discussion, 110v and 120v are synonymous as well as 208v and 220v.