This was originally posted on APC forums on 9/21/2012
I've read the documentation and tried multiple Group configurations. I can get RACS group configuration to cool my server room appropriately, but NOT with automatic fan control. The worry is that if our main building AC goes out, having it set on medium-low speed by manual control will not let it output enough to keep things reasonably cool.
In our raised-floor server room I have two ACSC100s with ducting configured like this: WALL - RACK - ACSC100 - RACK - ACSC100 - EMPTY area. The hot side has a door covering from the floor to the top of the rack, where we can move it to walk behind the racks. It's not sealed, but it certainly restricts airflow. We just set that up today when our maintenance guy came by - at his suggestion. He said the cool supply air was just going around the outside and into the return thus bad temperature readings on the return side, and a bit of inefficient cooling. We already have block-out spacers in the empty spots in the racks.
Like I said, it works great with the server room door shut - but in a perfect world it would have the fans on medium-low to handle our load, then in case of a major issue they could go to full speed without manual intervention.
Right now I'm running it full blast, more than necessary, and loud as can be just to be on the safe side. I have the fans on automatic mode, in RACS configuration, but the Setpoint for Supply Air is 64F and can't be modified in the web interface. It seems that is the reason it keeps running at full speed, but I'm not 100% sure.
My tests on Spot cooling also run fans at max. Testing In-Row cooling lets my actual servers get very hot, but Supply and Return values are normal.
Cool set: 73F
Supply set: 67F (except RACS seems to force it to 64F)
Deadband Set: 2F
Let me know thoughts, optimal configurations for my setup and any ideas. If there are any questions please ask, I'm very interested to solve this once and for all.