Supply Air Control Of Liebert DX Systems

[WillShank]

Have you heard about Hewlett-Packard's plan to modify the Liebert DX systems in their data centres so that instead of having the temperature sensor in the return air near the filters, it will be somewhere under the raised floor in the supply air? I have heard that Liebert is totally on board with this.

I work in a data centre that is managed by HP and I find this plan alarming. Maybe I am missing something but I see no benefits, only heartbreak. I see compressors short-cycling themselves to death.

I wish I could understand what is driving this forward and what the drivers expect to gain.

Comments?

[LU91Tech]

Here we go, computer geeks think they know what's best.

[The Doctor]

Cost savings. Expect to see aisle containment, remote sensors, arms waving with regard to the resulting "supply" temps, saber rattling, nuisance service calls, data analysts bellowing about plenum static pressures, networked units, more nuisance service calls...etc.
Then you can make up your own t-shirt

[Tommy knocker]

First I've herd about that. Can't say I agree with the idea. Sounds like someone with a bunch of letters behind their name trying to fix something that ain't broke. For see alot of problems since SA does not give a good measure of space conditions. Hard to control the humidity in the space if your not looking at the humidity in the space.

[chris4]

I have installed and serviced these Lieberts. They are called CRVs. Ive never seen one in a raised floor application. They are smaller and sit in the aisle between they servers. They can work off of supply air, return air or Hot and Cold aisle temps. The idea is to read the cold air blowing acroos the servers and the return is on the hot aisle. The humidity sensor is located in the return still. They can be networked so a group of units work as one. They have digital scroll compressors that load up and down for efficiancy. The comps are not really ever supposed to shut off, just stage down. And yes the I.T guys love to watch them and call for every little thing they dont understand and love to change the programming because they know whats best.

[Tommy knocker]

I have installed and serviced these Lieberts. They are called CRVs. Ive never seen one in a raised floor application. They are smaller and sit in the aisle between they servers. They can work off of supply air, return air or Hot and Cold aisle temps. The idea is to read the cold air blowing acroos the servers and the return is on the hot aisle. The humidity sensor is located in the return still. They can be networked so a group of units work as one. They have digital scroll compressors that load up and down for efficiancy. The comps are not really ever supposed to shut off, just stage down. And yes the I.T guys love to watch them and call for every little thing they dont understand and love to change the programming because they know whats best.

Cool. So the control is controlling off of both SA and RA. Haven't seen them yet so can't speek intelligently on how it works but sounds complex. Just the kind of set up a tech could make a living unf*#^ing after the IT team "fix" it every couple weeks.

[WillShank]

I see now that I should have also said, "modifying existing DX systems for supply air control".

[Eric S]

What I've heard about supply air control is that the unit stages the compressors to maintain a cold under floor temp, keeping a consistent temperature in the contained cold aisle. A VFD controls the fan to maintain the hot aisle temperature, increasing the airflow when the temperature rises.
Seems to me that humidity wouldn't be that big of a problem because the coil temperature would be as low as ever.