We have three water cooled air compressor of 450 hp each. As per manufacturer recommendation (Sullair), there is also a need of 21 000 cfm of fresh air ventilation for the heat released by the compressors casing (260 mbh).
We also need to keep the room in positive pressure to avoid exterior dust to come inside so I was thinking to install a make up air of 21 000 cfm with recirculation, power exhaust and drives on the fans. However, I find this system quite big and expensive.
The second option I was thinking is to rather use a 20 tons / 7000 cfm, DX roof top unit which is twice cheaper. I did a quick energy saving calculation and this solution does not cost more to operate than the make up air system since much less air is used. Does this RTU solution make sense for an air compressor room?