Server Racks

[RMERMP]

i found myself calculating for the heat dissipation of server racks. they have 12 server rack with 3000w per racks, that's 36kW total load of racks. how can i size up the air conditioning system of the server room. (the server room has only 12racks the UPS is separated to the adjacent EE room. thanks

 

[lukaiENG]

the short answer is (12) x 3000W = 36,000 W = 36kW ~= 10 tons for the IT load.
You should still account for other loads some of which will be dependent on your cooling system topology. lighting, PDU transformers, fan gain etc.
Based on your question I assume this is slightly outside your normal wheelhouse. You should be careful about clarifying and documenting the stated IT load. is this a design load given by the client? is it the UPS capacity supplied to the room? is this the nameplate of the servers going into the racks? typically servers will not operate anywhere near nameplate so bear this in mind.
You should also talk to your client about levels of redundancy, do they want one cooling unit sized for the capacity? do they want a back-up? do they run them both or operate lead/lag.

 

[ZDR1985]

Every watt of power used by a server is dissipated into the air as heat.

 

[lukaiENG]

Conservation of energy - where else will it go?
sure some will go into changing state of some electrons on the circuit boards and some will be turned into kinetic energy by the server fans, but in a steady state ultimately both of these and every other type of energy consumption in this space will become heat at the same rate that electrical energy is provided

 

[dbill74]

Just like you would any other electronic device in the space, only on steroids; it is 10 tons of sensible load.

Most server rooms I've seen and designed will have their own air conditioning units which are frequently located in the server rooms themselves. Commonly called CRAC (Computer Room Air conditioning) units, they are not designed for lots of ventilation air. Having a dedicated AC for server rooms allows them to be run 24/7 while HVAC for the rest of the building goes between occupied and unoccupied modes constantly resetting temperature set points.

When you do your air distribution layout, put diffusers around the perimeter of the racks or above aisles; locate return air grilles above the racks. This will help to keep the environment in the room more comfortable for the technicians.

Redundancy is highly recommended, how much is a conversation to be had with the client. Typically I've seen 2 units at 2/3 total capacity for the space. More units means smaller units. There is no code or guide that I'm aware of dictating how much AC redundancy to install, it will depend on available space and how valuable the servers are to the client.

 

[getitdone91]

Second or Third what everyone has already commented...
Your server load is all sensible gains. Obtaining accurate information about these servers is critical. Be aware that servers can have redundant power supply units, i.e. two 500 watt power supplies. When obtaining information from the client, I've had instances where they provided the sum of the power supplies (1000 W) as opposed to what is really being utilized (500 W ~ 250W actual). The diversity factor should be adjusted to the server room application.

 

[RossABQ]

The trend with servers is always towards server energy density increasing (per "blade"), I would establish with the client what scalability they want for your system. They aren't going to want to shut down while new ductwork is installed. That's why modular CRAC units are popular.