We are looking into cooling a small computer room on the weekend while the building A/C is down. Total load is currently 9000 BTU and will ultimately reach 12000. The room has a supply and return off the main system. The building uses a plenum return.
We are considering two options. The first is a spot cooler with exhaust into the plenum. The second is a 1-ton mini-split.
The spot cooler would cost roughly one-third what the mini-split would; however, our HVAC contractor has raised the issue of potential structural problems to the roof from dumping the heat into the ceiling without the main system running. Our building manager isn't sure it's safe, either.
If we need to install venting, the cost would rapidly approach the mini-split's. We own the building.
Thanks for any comments.