[AFMUG] Small NOC Backup Cooling

[Nate Burke]

I'm looking to add backup cooling to a small computer room, <200sqft.  
Primary cooling is via a RTU (roof top unit), but I can't put that on 
our generator (240v genset vs 480v RTU).  I'm thinking like a 2 or 3 ton 
Split system would be perfect.  Problem is we're in the midwest, and 
outdoor temperatures can drop to 0 or below over the winter.  Looking at 
the split systems, nobody seems to know if they will work for cooling 
with outdoor temperatures that low.  Online searching has yielded 
results for Heat Pump units, where they want to Heat with low 
temperatures.  Has anyone had experience with Split systems cooling with 
low outdoor temperatures?  Are there special compressors built for that 
use?  I have heard about putting a thermostat on the fan line to cut out 
the compressor fan below ambient X temp, or shrouding the compressor to 
keep wind from blowing through it.  But have not been able to confirm 
from any HVAC contractor the validity.

This would only be for backup use, RTU Failure, or power outage. The RTU 
is handling the load normally without an issue.  My Current Backup is 
Movincool units, but I want to reclaim the floor space, and make it more 
permanent.