datacenter build out and sizing

Europe doesn't use 115V. You will find 230V single phase and

That load would probably not justify a medium voltage feed. At least in the UK, you would probably be looking to use at least

You buy a UPS with the correct output voltage.

This will vary by country, supplier, and tarrif. Larger commercial customers will often have to pay a penalty for low power factor and/or high harmonic current content too (probably not at the power levels you are looking at though).

One other thing -- make sure you engage a local engineer familiar with local supply infrastructure and customs to do the design.

On 26 Feb 2007 10:16:23 -0800 essenz wrote: | I am not an electrician, but I would really like to get a good | understanding of some stuff so I can better estimate the costs | involved in building out a private datacenter. | | Here's what I know... I'll need the utility company to provide 3-phase | high voltage. I'll then need to provide a transformer and everything | else. | | My first question is how to size the transformer. | | My power requirements are pretty basic. 90% of the equipment in the | datacenter is 115V single phase, and occasionally you have a 230V | single phase piece of computer equipment. Some lighting, some office | wall outlets, and the AC units.

Quite a lot of computing equipment is switchable between 115V and 230V and generally does not care about the frequency. Most power suplies will run fine on 100 to 240 volts, 50 or 60 Hz. So saying "90% of the equipment in the datacenter is 115V ..." doesn't really ring true to me. Do you have that much old equipment than only works on a single voltage?

| Everything except for the AC units will be behind a 3-phase UPS. Most | models I price out are 460V 3-phase input.

So you'll have your transformer to convert 460V to utilization voltage following the UPS.

|>From an equipment standpoint, my 115V stuff will probably be 50kVA. | Not sure about AC units, but figure a 10-ton unit, or 2x 5-ton units. | | If the UPS balances my 115V equipment over all three phases, then I | dont need a 50kVA transformer for 50kVA worth of single phase | equipment, right? The transformer is rated in kVA for all three | phases, right? So I could have 70kVA of 115V stuff, and be okay.

Three phase transformer VA ratings give the total for all three phases assuming three phase balanced utilization. A 75kVA transformer will be rated 25kVA on each of the three phases. To select the transformer size you need, figure the worst case out of balance scenario you might ever have and multiply the worst phase by three. Then add a margin for growth (usually recommend doubling, but datacenters might need even more than that). If I had a datacenter starting out with 50kVA of load I'd be looking at 112.5kVA or larger transformer (and UPS).

| My other question is how do you bring down the voltage coming out of | the UPS. The UPS has 460V 3-phase input and output. So you can grab | individual phases on output, but wouldn't they be at 460V? How to do | bring it down to 115V?

That's what the transformer does. You'll need a separate transformer for the non-UPS loads.

| How finally, how does the power company bill usage over 3-phase. Is it | billed per phase, or all three. Say I am charged 7 cents per kW-hr, | and I have a 115V device running at 1000 watts. So on one phase out of | the three is in use. Do I pay 7 cents, or one third of 7 cents?