Chilled water expansion tank/pressure vessel/accumlator/bladder tank?

[andrew20441]

Hi
just been drafted in to finish a chilled water system that is half way through installation.....loads of issues however one at a time......

The system is on a mixed use building - 170 bed hotel, ballroom, theater, art gallery lalalalala

approximate volume 1000m3 chilled water - with approximate 400 fcu's and 22 AHU's....

The expansion and feed tank, open tank is a floor below the highest point and is currently sized at 2 m3.

The temp range - 5/6 - 14 + Degs C. I would therefore add another 5/10 degs as a diversity factor.

QUESTION:
Can i add a pressure vessel? Can i reduce the overall size of the pressure vessel instead of the 2 m3? Feed for the system can be automatic on a pressure switch?


Any advice???

[Magoo]

Hi Andrew.
1000m3 of chilled water is a lot of water, the specific volume and density change of water will be significant dependent on temperature changes. I have always used 2% of system volume as a header tank size factor. In your case 20,000 litres/ 10 tonnes a lot of weight in one spot, I would be inclined to use multi pressure compensation tanks spread around all the buildings.
Check www. engineeringtoolbox.com A lot of information re- header tank sizing.

[andrew20441]

ok...no problems for that..
The point at which the location should be ? Should it be higher than the flow and return on the closed loop system? (As heating systems the expansion tanks are always higher). The connection from the tank can be connected to the system by the pump on the return...?

[Magoo]

Hi Andrew.
header tank at highest point of complex and connect to lower pressure return water. Add auto air bleeders bottles all around the whole system. Plus after multi flushing of water in system and cleaning strainers, add chemical treatment to chilled water for PH control. Monitor PH regularly.