I'm a facility manager for a research lab at a major university (in the Northeast) and have an issue will cooling a "server" room. We had a 3 ton fcu installed that, until last winter, was sufficient enough to handle our cooling needs. Central Plant decided that during winter months they would bump up the chilled water temp to ~58F (I think it usually is ~45F). Their argument is that nature will provide supplemental cooling capacity and allow for substantial savings with plant chilled water. Not sure I can argue with that logic, until we have days where mother nature does not provide the needed temp.

Anyway, my question is that I need to determine how much cooling I have at 58F, so I can plan the heat load appropriately or determine how much additional cooling I need to bring into the room. I'm trying to track down the design specs. to see what water temp it called for to provide the 3 tons of cooling. I assume that there is some type of calculation I can do that will provide me with the cooling capacity at various temps (40, 45 and 50F).
I think it's prudent for me to plan for the worse case scenario and expect to have extra cooling when the chilled water temps are lowered for the warmer months.

Any help would be greatly appreciated.