We have been tasked with replacing an existing evaporator/condenser combination unit at a local resort & spa. The condenser is on the roof and the evaporator is in the basement. Rather than install a refrigerant monitoring system in the basement to bring the new system up to code, we are proposing installing an air-cooled chiller on the roof. The existing system provides cooling for a number of chilled water coils for comfort cooling in common areas.
I've included single line drawings of the existing system and the proposed new system. I'm looking for some advice to make sure we do not end up with a system that does not work efficiently... or at all.
Some key points we considered when selecting the new system:
-Added a buffer tank to prevent short cycling of the 70-ton Daikin Air-Cooled Chiller. Rough calculations from internet engineering sites lead me to believe we need to add a 300-gallon buffer tank.
-We opted to go with a primary/secondary system to avoid replacing the existing CHW pumps.
-The existing chilled water pumps are sized for the existing loop. The hope is that keeping those pumps on the secondary loop will continue to provide the correct flow & FTH to the secondary loop.
-We sized the primary pump to account for the new chiller design flow and additional FTH to pump the primary CHW to the air-cooled chiller on the roof.
-In theory, the new CHW pump, chiller, and buffer tank will create CHW and the secondary loop will continue to pull from the CHW buffer tank as if it were the original evaporator.
Am I on the right track? Do we need the buffer tank?
Should I keep the primary piping arrangement and replace the existing CHW pumps to accommodate the risers to the roof and ditch the buffer tank?
Any help & advice is greatly appreciated.
I've included single line drawings of the existing system and the proposed new system. I'm looking for some advice to make sure we do not end up with a system that does not work efficiently... or at all.
Some key points we considered when selecting the new system:
-Added a buffer tank to prevent short cycling of the 70-ton Daikin Air-Cooled Chiller. Rough calculations from internet engineering sites lead me to believe we need to add a 300-gallon buffer tank.
-We opted to go with a primary/secondary system to avoid replacing the existing CHW pumps.
-The existing chilled water pumps are sized for the existing loop. The hope is that keeping those pumps on the secondary loop will continue to provide the correct flow & FTH to the secondary loop.
-We sized the primary pump to account for the new chiller design flow and additional FTH to pump the primary CHW to the air-cooled chiller on the roof.
-In theory, the new CHW pump, chiller, and buffer tank will create CHW and the secondary loop will continue to pull from the CHW buffer tank as if it were the original evaporator.
Am I on the right track? Do we need the buffer tank?
Should I keep the primary piping arrangement and replace the existing CHW pumps to accommodate the risers to the roof and ditch the buffer tank?
Any help & advice is greatly appreciated.
