closed loop chilled water system high pressure

[AstroHouse]

I have a new system that seems to be suffering the problem of the chillers not being able to maintain the setpoint:

equipment:
3 turbocor chillers rated 550Kw each each with a fixed primary pump set at 19 l/s
3 secondary pumps with VSD however using two N+1 controlled by static pressure sensor
my chiller plant is on the ground floor and my secondary pumps are on the first floor, the secondary system supplies water at 18 deg to a 400kw plate heat exchanger and the distributes to several CRAC units.
the design load is 750 Kw and we are running at 300kw.
The design consultants are insisting that we run the system at 5,2 bar system pressure (I cannot understand this) this means that I end up with my secondary pumps running at 93%. and the return flow 54 l/s shooting past the chillers around the balance loop and mixing with the chilled water giving me an elevated temperature.
I have successful proved that I can run the system at 2.5 bar (I would have gone lower but my alarms would not allow it. I have stated that I do not require 5.2 bar as I have a closed loop system and all I am worried about is flow. could someone please take me out of my anguish state.
Sorry the chillers cannot handle the setpoint and a second chiller has to come on to get down to set point, yes you are correct the cycle keeps repeating.

 

[ChasBean1]

AstroHouse, similar to my misunderstanding of why my fellow Americans perceive and vote the way they do, I'm outsmarted by your post as well. Can you clarify the question and maybe provide a diagram?

 

[AstroHouse]

basically I have a closed loop chilled water system set up as a fixed primary-variable secondary, controlled via static pressure switch.
my highest point is 25ft above ground level. my understanding of hydraulics is that if I have a closed system then all I require to do is overcome the friction created by the pipework and fittings and therefore should be running my pumps at minimal speed with a low pressure of approx. 2 bar.
My designers are stating that when they carried out full load tests @ 700kw they required 5.2 bar of pressure to maintain the load, I am running 300Kw of load and they still want me to run at 5.2 bar pressure, please can someone clarify. I could send you a drawing if you were to give an email address

many thanks

 

[RossABQ]

What pressure is the make-up water regulator set at? It sounds like you are setting system pressures with the pumps, not the make-up regulator?

 

[AstroHouse]

RossABQ thank you, I have checked and the pressurisation unit is set to 3 bar, however this does not solve the problem of why the pressure should be set so high. my chiller's are on the ground floor the primary pump takes it up to the first floor where the secondary pumps are located (20ft max) and my discharge header (I have 3 secondary pumps) is 5ft above this. all exchangers ect are below this level on the ground floor. If you go by the rule of thumb 1psi = 2.03ft then my pressure should be around 1 bar or am I missing a trick

many thanks for your response