I'm looking for advice on which electrical service I should have run to a rack that I have in a data center.
The price is the same for either a 30 AMP 220V circuit or a 60 AMP 120V curcuit.
I realize that these two curcuits are delivering effectivly the same amount of usable power, however I'm curious if one is better than the other. I remember reading somewhere that 220V is more effecient than 120V. If this is true then I'm wondering if that would result in my ability to run more devices off of the 220V power vs. the 120V.
Thanks for any help!
EDIT – This will be running in the US. All servers and Cisco gear that we are running can support either 120V or up to 240V. They are auto switching power supplies. Therefore locking power cables will not be an issue and standard plugs into the servers will be used. This will also be redundent circuits so I will be balancing each one to around 40% load so that in the event one circuit goes down then the other can carry the full load at or around 80%.
Best Answer
You are getting the same amount of 'power' either way (120V x 60A = 240V x 30A), so from an electrical "power" standpoint it is a wash--either one will support the same amount of equipment in the rack...
You should do some research to be certain, but most modern computer equipment is equiped with switching power supplies that accommodate a wide range of voltages (manufacurers don't need to stock a separate power supply for each country; instead, they simply ship the appropriate power cord for the destination country). Given that, your equipment most likely will not care whether they have a 120V or 208V or 240V input--so long as you have the appropriate power cord to connect the system to the power distribution module.
My understanding from engineers at colocation facilities I've worked with is that most switching power supplies are a bit more efficient with a high voltage input (e.g. they produce less heat, which is wasted energy) which can save a bit on both power air conditioning load. The wire gague required to carry the same power at 240V is smaller and more flexible than the heavier wire required at 120V, which may be a convenience when routing cables within the rack.
I would confirm that all of your equipment is capable of accepting high-voltage power; if so, obtain the appropriate power distribution module and cordage to connect your equipment to the 240V 30A circuit.
Remember, too, that a 30A circuit should not be loaded up with 30A of equipment--you need to leave some "head room" to ensure that the circuit is not overloaded (I believe the rule is to stay below 80% of the maximum rated capacity (e.g. maximum 16A continuous load on a 20A circuit; no more than 24A continuous load on a 30A circuit).