Re: T1000 = Insanely noisely

ChrisQuayle wrote:

Perhaps Sun only used single speed fans on their older kit. More modern 51-35

kit tends to use variable speed fans that adjust to airflow temperature. However, a lot of server class kit is rated up to 40 C ambient and you need to shift a lot of air at that temp to maintain internal temperatures at safe levels. Lower cost kit may claim that rating, but I doubt if a lot of it been seriously tested in the way that high end vendors do. During design test, a large server will have hundreds of thermocouples throughout the system to make sure there are no hot spots and it will be tested in a wheel in environmental chamber at peak temp for days or even weeks - the airflow throughout the system is adjusted until everything is well within rating at max rated temperature. On a 1 2 3u system, that often means small, noisy, high speed fans...

Chris


Another issue is altitude. If something is rated for use at high altitude, its fans must be oversized when used at lower altitude. The reason is because its the *mass* of air per minute that affects how much heat is removed, not the volume flow rate. So at high altitude, the flow rate has to be higher as the air is thinner.

I have a valve (tube to Americans) for which the data *** gives air flow needed at various temperatures.

http://www.g8wrb.org/data/Eimac/3CPX1500A7.pdf

At sea level, with an air inlet temperature of 50 deg C, for maximum dissipation (1500 W), a flow rate of 35 cubic feet per minute (cfm) is needed.

Increase the altitude to 10,000' and that goes up to 51 cfm, which is a very substantial (46%) increase.

So if you Sun seems overcooled around sea level, you may well find it is not if you move it to somewhere where the altitude is high. I'm pressure sure my Ultra 80 is rated for use at 10,000', although my altitude is about 150'.


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