Hi I'm just a layman and a newbie at HVAC. I am looking for second or third opinions on the advice that we're getting from a local HVAC engineer.
We have a computer room that needs more cooling capacity. Currently there are 2 cooling units, about 5 tons each. This has been adequate, until one of them fails. Also we are adding a lot of computer and network equipment and expect to add a lot more. We expect to need 25 -
30 tons at the end of 5 years from now.The computer room has a raised floor with only cabling underneath and no room for anything else. There is a drop ceiling, which contains the supply and return ducts. The air cooling is done in a room in the floor above. Apparently there is no more room above the drop ceiling for more ducting. The approach we've been using so far is the cold aisle/hot aisle method, where you dump cold air in the aisle between two rows of computer racks, suck the cold air through the computer equipment and dump the warm air in the aisles behind the racks, where the return ducting sucks up the warm air. Seems to work fine.
We've hired a local HVAC consulting engineer but I'm not sure he's had much computer room experience. We don't want to put additional cooling units inside the computer room itself. His advice was to add a mechanical room to our building right next to the computer room (ground level), put the cooling units in the mechanical room, and punch holes through the computer room's outside concrete wall for the ducting. There would be 2 Lieberts of 25 tons each. The supply ducting would be two semi-circular rings that run just under the drop ceiling and right against the walls. There would be no return ducting, just two big return vents built right into the outside wall back to the cooling units.
So it looks to me like he's just going to let the new cooling units cool the room air as a whole, instead of dumping the cold air in the cold aisles. He seems to know what he's doing but I don't know if this approach is OK. I guess he's depending on the air to just mix around but is that good enough? I know he's really overloaded with work so I'm just a little nervous that he may not be putting enough thought into this, but I don't know enough to question his approach.
Any thoughts or advice?
Thanks. Armin