No matter the number of server racks you manage, we have all seen an increase in equipment density over the past few years. This growth has caused many to overload their 110v circuits, required additional circuits be added or even additional racks. For small to mid size data centers and IDF rooms, there are advantages to using high voltage (208V) power over the standard North American low voltage 110V power. Compared to 110V power, 208V circuits allow you to nearly double the amount of equipment on an electrical circuit, increasing your equipment capacity. 208V power can even reduce your total power consumption, saving both money and the environment.
Almost all equipment today is manufactured with universal power supplies. These power supplies recognize the input voltage and adjust accordingly. However, the number of watts required to operate the device remains static. Using Ohms Law, in a very simplistic form, watts = voltage x amperes, devices running at 200 watts would require 1.8 amps at 110V, while that same piece of equipment would only use 0.96 amps on 208V power. A 20A circuit loaded to the derated maximum, 16A, would allow for 8-9 devices operating at 110V, but a similar 20A circuit operating at 208V would accommodate 16-17 of the same devices. This effectively doubles the potential equipment density.
In a raised floor environment, this will allow you to operate with fewer power whips under the floor. Fewer whips translate to fewer circuits to manage, and reduced clutter below the floor, which improves airflow. This improved airflow lowers the cost of cooling the environment and lengthens the life your servers and air cooling equipment. Considering each watt of power used to operate your equipment requires nearly a watt of cooling energy, the improvement is significant.
Operating at 208V also improves the efficiency of the power supplies themselves. 110V AC power consists of a single live line and a neutral line with the voltage oscillating in wave form. In contrast, 208V power is created by two live lines. (see below) The two phases of 208V are offset 120o, so that they are never at 0 volts at the same time. This allows the power supply to operate more efficiently, and can create a power savings of 4-6%.
High voltage 208V power may not always be an option in the environment you work in. And retrofitting your entire center would be expensive. However, the additional rack density, improved cooling and airflow, and 4-6% power savings should make 208V an option worthy of consideration where available. As always, check your equipment to ensure correct operating specs and check with your electrician and/or facilities manager for code requirements.
