# How to determine Server Room size and power requirements

Dear Community.
I am responsible for allocating size for our company's server room. We are soon to be purchasing some servers. My questions are,

-How do I choose an appropriate size for my server room given the number or footprint of my servers? (Does this answer cater for growth?)

-How do I calculate my electrical power requirements for my servers to that I can allow an electrician to do proper electrical wiring?(Does this answer cater for growth as well?)

Many thanks!
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Commented:
The manufacturer of your servers will publish the power requirements for each server whcih you will need to multiply by the number of servers.  It is better to err on the side of caution with this and work off the maximum power requirements for the server during startup and on full load.

For power, you will need to factor in other equipment as well (swiches, firewalls, routers, storage, monitors etc).  The power requirements of all of these items will be available from the manufacturer.

Add the figures together, and that will be your maximum.  Then add 50% for growth.

You will also need to allow for cooling of all of the hardware and the information is also available frmo the manufacturers and again, add 50% for growth.

With regards to room size, allow plenty of space for air to flow around the servers and space for you to move round.  If you have one standard sized rack, then a room size of 3m x 3m would be the minimum I would consider and I would only consider something that small if nothing else was available.
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ExpertCommented:
Regarding the power, APC has a nice calculator: http://www.apc.com/tools/ups_selector/index.cfm

Will give you an estimate of your power requirements.
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Commented:
For the electrician, you need to round up:

UPS1:
servers, monitor(s), external drives, etc = 810W
need growth? = 1500VA UPS
for the electrician = 120VAC/20A circuit with NEMA 5-20 receptacle

UPS2:
server, monitor(s), external drives, switches, etc = 1500W
need growth? = 3000VA UPS
for the electrician = 240VAC/20A circuit with NEMA L6-20 receptacle

The electrical requirements should be specific to the equipment boilerplate rating, not just "give me a total of __ amps" or guessing by the average amperage draw at any one time.

Your circuits need to be de-rated (to 80%) to accomodate a full-time load.  So, plugging a 1500VA piece of equipment (regardless of the live load _now_):  1500VA / 120V = 12.5A / 0.80 = 15.625A circuit rating.  You can't use a 15A circuit...you must go up to 20A.
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PresidentCommented:
You are going about this the wrong way.  First, have the electrician you will use get an ammeter and measure what you are using now.  If you are not on 220 VAC, then this is the time to go to that as well, as I expect your UPS can take a 220 load.  This is more efficient.

Your UPS's probably have a SNMP board you can add that will report peak and average requirements as well.

So I would really just defer all of this to an electrician who is experienced in data centers.  You simply can not risk screwing this up, and electricians know about power sequencing and startup loads, and current requirements for AC and everything else.  If you do this yourself with some online tool, or reading specs, then risk is too high of missing something, or being way off.

An electrician also has to allow for a certain fudge factor to meet code anyway, so this whole effort on your part is going to get redone by the electrician no matter what.
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Commented:
>so this whole effort on your part is going to get redone by the electrician no matter what.

Excellent point, dlethe.  Electrical plans have to go through a qualified engineer, permit office, and inspector.  None of those will accept your notes or estimations as final data.
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PresidentCommented:
Right, the power requirement is what it is, and that is not going to change unless you were previously using 120VAC.  Whether it is 10KVA or 100KVA, your hands are tied, except when it comes to the thermostat.
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