# Thread: Cooling / power calculation questions

1. Web Hosting Guru
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## Cooling / power calculation questions

The company I work for is starting to have some cooling issues in our server area. We have basically doubled our server equipment in the room without upgrading the air conditioning unit in the room. Temperatures are getting really high in the room (sometimes reaching 85F which is just WRONG!) and we are trying to get it replaced. Since my boss is the one making decisions I thought I would try to help him out a little bit with some of the information/calculations he needs.

My questions are:
1. When calculating watts for a redundant power supply do you double what the power supply is rated for? So on one Dell PowerEdge 2950 it shows that I have a 750W redundant supply. Would that be 1500 Watts?

2. Do you calculate your cooling needs for max wattage or do you calculate a percentage of what each power supply is rated for?

3. What percentage would you multiply your final total Watts by to accommodate possible future additions? 10%? 25%?

We currently have:
2x PowerEdge 2950 - 750W Redundant
1x PowerEdge 1950 - 670W Redundant
2x PowerVault NX 1950 - 670W Redundant
1x PowerVault MD3000
3x APC Smart UPS 3000
1x APC Smart UPS 1400
2x PowerConnect 6224
2x PowerConnect RPS-600
3x PowerConnect 5324
1x Cisco 2801
1x Cisco 2821
3x Unknown wattage servers redundant power(All the same specs)
1x Unknown wattage server redundant power
1x Unknown wattage single power supply
Then a few other small devices like external modems, KVM and a small-mid sized phone system.

I am not an electrical expert but I am calculating that it is going to be about 10,000 - 12,000 Watts?

2. Web Hosting Guru
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Jun 2004
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I would suggest you contact a HVAC contractor that is experienced in cooling of datacenters. Let them evaluate your needs. The additional capacity can be built in; but remember hopefully, the newer equipment is also getting greener. (More energy efficient, so your near future needs may go down.)

The air conditioning unit is not a standard unit like you would think of like you have at home for instance. The AC compressors will not function when the outside temps get low, so the outside unit has heater coils to make it function in the winter.

And don't forget about that one tech that insists upon having the 1800 watt space heater under their desk to keep their feet warm.

3. Web Hosting Guru
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The air conditioning unit is not a standard unit like you would think of like you have at home for instance.
Correct, we currently have a closed environment system that has the HVAC unit in the ceiling circulating the air only in that room.

I did just after posting this thread find:
Dell Datacenter Capacity Planner, which I am using to calculate some of the numbers.

But using that tool shows that a server with a 750W PSU is only putting out 395.7W of power. So does this mean you do not calculate to the full 750W max?

4. Web Hosting Guru
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Jun 2004
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Hi Daniel,

I was assuming that you had a closed system... my point being that the outside air compressor for a datacenter that potentially needs air cooling capacity in the winter time is not the same type as a summer only ac compressor. The "winter use" ac compressors have heater coils outside on the ac compressor.

Normal AC compressors (outside unit) do not operate when the outside temperature is below 50 degrees.

Not all AC contractors know about winter use ac compressor units.

5. Web Hosting Guru
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Good to know. Thanks for the info.

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