High humidity in the Data Center. Any advice?
We are having an issue with humidity levels of 65% in our Data Center. I know we should be below 55% but I was wondering if our level will really hurt the equipment. Do i need to replace my overhead coolers or can I live with this?
Thanks
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ASKED:
November 6, 2008 4:29 PM
UPDATED:
July 12, 2011 1:15 PM
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Answer Wiki:
65% should not be a problem.
The standard computer room humidity is 45 to 85% but the important issue is the rate of change in Temperature.
High Humidity is only a problem when the temperature drops suddenly, if the temp is high with a high humidity and the temp drops rapidly the moisture can drop out causing moisture corrosion on terminals and hardware.
But in my 25+ year experance I have yet to see it occur in a correctly design and operated data centre. I have seen it occur in a server room where the A/C was too large for the load and space and the unit controls were faulty.
The Humidity rating quoted by a supply is the normal operation range to try and stop both moisture drop out with high humidity and static electricity problems with low humidity.
In temperate climates a lot of data centres turn of the humidification and heating to save energy as 99% of the time the extremes of the humidity are not reached.
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In the literature, I generally see recommended relative humidity ranges listed as 40% to 55%, with ranges of 20% to 80% usually considered acceptable.
You should investigate, however, why you are having humidity problems in your data center. Since servers don’t sweat, most data centers have few people working in them, and cooling coils dehumidify, where is the excess moisture coming from? The only two places I can think of are unconditioned outside air, and CRAC (computer room air conditioner) units fighting each other.
The more commmon problem is CRAC units fighting each other: some units are cooling while others are humidifying. Adjusting the controls or replacing the CRACs with a central system would generally solve the problem.
The other possibility I only saw once: a building originally designed as a warehouse was converted to a data center, and the owners tried to save money by keeping some of the original AC equipment. Air handlers dumped filtered but unconditioned air into the space for ventilation. Since this was a costal city many times the air was humid. When the humidity level rose they had to shut off the air handlers until the AC system could get the moisture out of the air. I recommended a variable speed drive on the air handler to slow down the rate of delivery of outside air to something the AC system could handle but still deliver enough cfm for ventilation.
The one recommendation that I have is what ever you do, make the changes in small steps. Change a setpoint by one or two degrees and then let things settle down for a day or two. If you go making too many changes to quickly, you never know what fixed the problem or what made it go the wrong way.
Is there a way to determine when the humidity in my data center is becoming critical? Is there any tell tale signs i will observe?