Data Center Air Quality

[Dymalica]

A lot of concern these days with energy usage in Data Centers. More and more people are looking at rooftop units instead of the CRAC units because of the economizer function. There is also the concern about bringing in outside particles and dirt that can damage the server equipment. What do you guys recommend to bring in the cleanest air yet save energy? I know that we could put in high MERV filters >15 which would help, but a lot of stuff could get through the cracks of the filters. Every couple of years we have forest fires in the area, and I am worried that smoke will infiltrate the server area as it did our office. Is there a air monitoring device for dirt particles in the air? Would would you recommend doing/installing?

 

[zuccus]

You could use water side economizing in your chiller plant. This would eliminate the air filtering issues. Effectively turning off your chiller power consumption. When done right this can be very effective.

Air filtering is a lot tougher than it sounds, and very easy to mess up.

Zuccus

 

[ChasBean1]

The world’s gone to the recirculating computer room air conditioning units in droves because of the tight control, but it’s all mechanical cooling and it can be energy intensive. Try a heat recovery wheel or a typical return air AHU with economizer and good filters.

Where I am, at least 50% of the year the spaces could be cooled without mechanical refrigeration. There are no ventilating requirements so a typical return air unit with economizer could reduce to ~0% outdoor air when max summer cooling is needed.

Stick with the CRACs, by Liebert or other, if you have a free cooling method (keep in mind ‘free’ is a relative term)…

 

[RossABQ]

I just don't understand the paranoia of the IT folks WRT OSA economizers. I was in a meeting where one of them made the statement that if we used OSA econ "there will be dirt a foot deep" on the racks in a year. Across the parking lot from the DC is a semiconductor fab running over a million CFM of MAH's and achieving Class 1 or better. The technology is there, and an couple inches of static pressure is still a lot cheaper than running chillers, or even a "free" cooling wetside economizer.

Best way to save energy? Let the DC be 85 degrees. The servers don't mind a bit. It's just the IT folks don't have the huevos to do it. IBM servers are OK with 95! With those kinds of temperatures, all kinds of free cooling become practical.

 

[mauricestoker]

Sounds like the ASHRAE 2008 recommendation.

Nice thing about using a separate AHU with economizer is the humidity can be more easily controlled than multiple CRAC units. Both air side for the AHU and waterside for the CRAC's can use economizers.

Using hot/cold aisle, with the higher supply temp recommended by ASHRAE (and Ross, as above) will save lots of cash. Putting barriers to direct flow from the CRAC will also save energy and reduce particulate entrainment.

If air quality is a concern, I'd recommend starting with EPA air quality readings.

 

[ChasBean1]

One thing about the dust concern that's a little ironic - a lot of these server rooms might have a dozen or so CRACs serving a common duct or under floor plenum but don't need all to run to meet load. As soon as one is turned off, air backfeeds through it and the dust that's gathered on its filters gets dislodged and goes back into the room. For this kind of installation, each unit really should have some low leakage isolation dampers.

 

[RossABQ]

Very good point, Chas! I've never seen a CRAC with anything like that.