chilled water system pressure

[abo5der]

hi all ,
should the chilled water system (ie,20 floors tower ) be pressurized before running the circulation pumps ?
when the pumps are off ,the static pressure at the pumps suction and discharge is 9.5 bars .

 

[GMcD]

The system pressure should be set up to make sure you are at least 2 bar at the top of the system, or more, depending on your system volume and temperature difference - chilled water will contract as it's cooled down from ambient, and the expansion tank on a chilled water system needs to be pre-pressurized with a certain content of water, so when the system begins to operate and the water volume "shrinks", then that water can make-up for the shrinkage and still keep the top of the piping system above your minimum desired pressure.

 

[Drazen]

in general there is recommendation of 0,3-0,5 bar on system top, which mostly depends on how precisely you can set your pressurization system.

pressurization serves only to prevent underpressure on the top of the system, which would suck the atmosphere air, the lower you set it the better, given that you are certain that underpressure will not occur. for smaller systems it is common practice to design to zero, means equal atmospheric pressure, and during start-up fitter will make just tiny increase in setting.