Makeup pump for tower.

[SAN888]

Dear all,

Please help me to understand about the makeup pump design.

Open head of chilled water pump as follows:-

Discharge- 700kpa

Suction -420kpa

Head of pump - 292 kpa

What pressure I can set the makeup pump for cut off.

Whether delta of discharge or suction or suction pressure.

Please help me to solve this .

Regards

Sandy

 

[lukaiENG]

If I understand the question correctly you are asking what pressure you need to set a make-up water pump for maintaining water volume in a chilled water system.

Where in the system does the make-up pump connect? The pump must generate enough pressure to push water into the system at the location of connection - you need to figure out what the pressure is at this location.
If the make-up is connected immediately before the pump, it needs a set point of 420 kPa.
If the make-up is connected immediately after the pump, it needs a set point of 700 kPa.
Any other point will require a set point somewhere in-between.

I've always found it best to provide make-up at the point of system pressure/expansion control (the expansion tank). This is the point where the system pressure is set, therefore it is the one point you "know" precisely. You can get combined expansion tank/pressurization/make-up units which make all this very simple.

Note, one of your readings is wrong*, head of pump = discharge - suction (700-420 = 280)
* unless your suction and discharge points are measured before/after other components (strainers, valves etc)

hope this helps.

 

[lukaiENG]

just noted the subject referred to a tower. is this an open or closed tower?
if open there will be no expansion tank obviously.

all other comments still stand

 

[willard3]

I don't understand the question.