Earlier this week, the weather forecast was for cooler weather in our area by this time.  We could really use a small Ice Age in our server room right now.  ;-)

What happens when you put 40000 BTU/hr of equipment in a server room with 3 tons of AC cooling capacity?  For those less familiar with server room and HVAC design, 1 ton of cooling capacity can handle 12000 BTU/hr of heat generated by equipment.  So the answer is - we have probably exceeded our cooling capacity.  I say probably since most of the servers aren't drawing the full power possible from their power supplies.  While most large companies with data centers or server rooms probably have sufficent space and capacity for growth, small and medium size companies may perhaps be more limited.  

Several employers ago, in a small office, we used a closet as our server room.  Yes, really, a closet.  Now at the time, we only had 1 server and 1 frame relay router and we did have an air vent in the closet, but we were pretty restricted in terms of future growth due to the lack of ability to handle heat dissipation.  Eventually we did move the equipment to an actual room which had better airflow.

Currently, where I work, we have a server room that we designed more than 4 years ago.  We have a Liebert air handler with a 3-ton condenser outside.  When we started, we had two computer racks, 1 comm rack and we planned extra capacity to be able to add 2 more racks of equipment.   We had sufficient dedicated power circuits, generator capacity and cooling capacity to handle this planned growth.

Four years and now four racks later, with many more smaller computers packed with multiple CPUs and lots of disk drives, plus miscellaneous other equipment, we walk into the server room and notice that it's a little warm at times.  When one or more admins work in the room for 30 minutes or so, we notice it gets much warmer.  The human body is a pretty good furnace.

We are currently researching options to either upgrade our main AC system to have a higher capacity or to add additional small cooling units in the room up on the walls.

This is just a reminder that as IT admins, in addition to protecting our data by making backups, patching systems to remove vulnerabilities and using defenses such as firewalls to reduce the potential unwanted exposure of of our data, we also need to be cognizant of our physical infrastructure and capacity.  

If we don't have enough power, our systems turn off.  Operationally, this is bad but at least the system will most likely boot back up once power is restored.  

If we don't have enough cooling, again our systems may go offline, perhaps in a more permanent manner.  While not as a result of our current AC issue, we have previously seen servers where the CPUs melted down and caused a fire in a server.

Update 1:

We got a post from Alan with some information about how to determine the heat load of your equipment:

	max BTU/hr = 3.412 * (max Watts)
	max Watts = Volts * max amperage

	thus 

	max BTU/hr = 3.412 * Volts * max amperage

He also passed along rack configuration links from Dell and IBM that help you determine the total power and colling requirements for the equipment in it.