This question was originally posted on DCIM Support by pcompany on 2016-10-27
Nowadays, I operate a Date Center with HACS containment, and DX CRACs with 19°C supply air setpoint and I want to set supply air setpoint to 21°C , my configuration is on fan speed preference medium (AT 11,1°C), but the threshold on the Netbotz 550 are on 34°C on the return air to CRACs DX, and the alarm goes up early. Please can you help me to known what are the maximum temp. recomended on hot aisle to set my new thresholds, if possible for rack server and rack network.
This comment was originally posted on DCIM Support by Ditte Drewer Mathiasen on 2016-10-31
Hi pcompany, thanks for posting. Lets see who can be of assistance here. @community any ideas? Kind regards Ditte
This comment was originally posted on DCIM Support by Stine Hansen on 2017-01-03
Hi pcompany, sorry to have left you hanging. Have you found an answer to your question?
This answer was originally posted on DCIM Support by Balaraman Jagadeesan on 2017-02-14
I would suggest you to set the threshold on the Racks Inlet temperature since your DX CRAC unit control is on the Fan Speed Preference to maintain the supply air temperature to the racks.
I also suggest to you to consult your cooling team who planned the HACS solution also for the threshold range which needs to be set in order for you to get an alert on the cooling unit operations status. Since the operation of the cooling units depend upon the control selection. Maintaining the Inlet Rack Temperature of the racks is utmost priority, I would also suggest you to set the threshold as per your data center requirement if you have the Netbotz temperature sensors at the racks inlets. As per ASHRAE TC 9.9 regulations-2008 version, it states to maintain the rack inlet temperature between 18 degree Celsius to 27 degree Celsius for Class 1 and Class 2.
From APC APPLICATION NOTE #146, it states that InRow® cooling products have multiple modes of operation for system control. When placed in a hot aisle containment system, the InRow® cooling unit must be set to RACS / HACS to ensure that the system is operating properly. In addition, the HACS mode has two set points that must be configured. These set points are “supply air temperature” and “fan speed preference.” In this mode, the cooling set point will have no effect on the operation of the unit. This is because the cooling set point looks at a remote temperature probe in an open-row configuration in order to maintain the inlet temperature to the adjacent racks. In a HACS configuration, the temperature of the supply air (discharge from the unit) will be the same as the inlet to the IT equipment because it will not have a chance to mix with the surrounding environment. In addition, the InRow® cooling unit must respond much quicker in HACS mode to ensure that spikes in rack exhaust temperature that occur over a time scale of a few seconds are properly neutralized.
I hope this helps. I am not an expert, but would like to share my opinion. I also let other community experts to share their views.
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