Chilled water bypass problem

[MACT]

I have a question, does anyone have an opinion as to the best place to locate differential sensors in a chilled water system to control the chiller bypass. The system comprises of 3 off 3,000 kWR chillers and a single 1,00kWR, with the bypass in the chiller plantroom. The chilled water loop is large and during some conditions the system pressure falls and certain areas lack chilled water flow. This is a tricky one as starting multiple chillers to get the correct flow is not the most efficient way. Currently the sensor is in the plantroom about ten metres past the bypass.

[Brian_UK]

Has the system been balanced correctly, or, if it is an older system, does it need rebalancing.

[MACT]

The system is balanced as well as it can be, but considering there is about 2km of pipe, 30 AHU's and 50FCU's I am not about to do a system rebalance. The question really is does anyone have any design experience with sensor location, is it better to have the sensor close to the chillers or better further away. Obviously the static setpoint will change due to friction losses the further down the run you get but that is easy enough to calculate.

[vijay_study]

Hi Mact,

Are you using primary only variable pumping system or primary secondary variable pumping system.

Regards

Vijay Kumar

[Renato RR]

Do you have some drawing of system?

[MACT]

Sorry no drawings renato, the system is primary pumping only with no variable speed, each chilled water pump and chiller comes in based on calculated loads from return chilled water temps. There is no problem with water temps, just flow to the field drops if enough chillers aren't running and a heap of valves are open. What I may do is log the system pressure and various other points to check if there is a lag in the control design, or if the pressure sensor is accurate. I will also be able to find a far better sensing point further down the index run this way. THanks for all your help guys.