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  1. #1

    Question Re: High Delta T Across Coil, CRAC Units, Data Centers

    I would like you to educate me. In a data center environment with CRAC units and hot and cold aisle containment, what does it mean to say that the CRAC units want to see a high delta T across the coil? What is a delta T? What is a high delta T? What type of coil?

  2. #2
    Join Date
    Jan 2010
    Location
    Central Texas
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    159
    Delta T is the temperature differance between the Return Air and Supply Air Temp. Ideally you should expect a 16-20°dT across the coil. The difference in CRAC units is the fact that they run at 600cfm per ton compared to the 400cfm per ton for Comfort Cooling units.

  3. #3
    Join Date
    Apr 2012
    Location
    winnipeg
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    1,330
    how does moving more air give you a higher t.d.
    it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair

  4. #4
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    Apr 2012
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    Paper Street Soap Company
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    It doesn't. Who told you Cracs need a high delta t ? Bogus.

    Hot aisles are the aisle where the hot air from the servers is discharged. Above that aisle if you have a conditioned grid plenum will be your return grills.

    Cold aisle will be where the upflow vented tiles are located at the intake of the servers.

    Also hot and cold aisle is an obsolete setup.

  5. #5
    Join Date
    Jan 2010
    Location
    Central Texas
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    Moving more air per ton means the sizing of the equipment will have to be engineered to handle the increased load of the increased air flow thru the coil and still maintain the 16-20°dT thru the coil.

    If you were to just increase the CFM thru a Comfort Coiling system, the dT would just drop. This is a common problem with Engineers or HVAC Salesman that just think a Comfort Cooling system can be used in a Telecom or IT/Data Center.

    Comfort Cooling equipment is designed to remove Latent Heat (Humidity) and Sensible Heat, where Critical Cooling (CRAC Units) are just going to remove Sensible Heat (The heat that you feel). So if a Comfort Cooling unit unit was installed in a Critical Cooling enviroment it would have to be oversized to handle the actual Sensible Heatload and risks drying out the space to the point that Static Electricity can damage the server equipment.

  6. #6
    Join Date
    Apr 2012
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    Paper Street Soap Company
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    Cracs have humidifiers.

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