Constant speed air cooled chiller with VPF Pumping is used for the above case
Jong Fung Swee
Aug 2
My two cents:
First, the FCUs are installed based on peak room requirements, but the chilled water system is designed on diversified actual building demand.
Second, CHW flow is modulated by PICV (Pressure Independent Control Valve) at FCUs. When a zone reaches its setpoint, the valve closes or throttles, reducing flow demand.
Tis is due to at any one time, the actual GPM needed is only for the active zones, not for all 1450 TR FCUs running 100%.
Abdul Rahman
Aug 2
Diversity factor reflects that not all FCUs will run at peak load at the same time. Especially in office buildings:
Some areas may be unoccupied.
Different exposures have staggered loads.
Internal gains vary by floor/time of day.
You install chillers with a total capacity of 1160 TR. This is based on simultaneous peak demand.
FCUs connected may require 1450 TR ร 2.4 GPM/TR = 3480 GPM total (connected). But chiller will supply only 1160 TR ร 2.4 = 2784 GPM.
Use 2-way valves on FCUs (Variable Flow System):
Only FCUs that need cooling will get water.
Flow adjusts dynamically via differential pressure sensor and VFD pumps.
Balancing valves, or PICVs (Pressure Independent Control Valves), help regulate flow.
Use differential pressure controllers to ensure that when many FCUs are partly loaded, the system doesnโt over-pressurize and misbehave.
So balance the system based on connected flow, but pump the system only for the actual load demand.
Yu Chang Zhen
Aug 3
Hi Kiran,
In extent to the above sharing, I would add that all FCUs should be tested to their design flow rate. If all FCUs are ON at the same time, you may not get full flow due to diversity design. Hence, group them as per your design basis for diversity and test them in groups. That way, you ensure all FCUs can meet their designed flow and the chillers can be tested to full load.
Constant speed air cooled chiller with VPF Pumping is used for the above case
My two cents:
First, the FCUs are installed based on peak room requirements, but the chilled water system is designed on diversified actual building demand.
Second, CHW flow is modulated by PICV (Pressure Independent Control Valve) at FCUs. When a zone reaches its setpoint, the valve closes or throttles, reducing flow demand.
Tis is due to at any one time, the actual GPM needed is only for the active zones, not for all 1450 TR FCUs running 100%.
Diversity factor reflects that not all FCUs will run at peak load at the same time.
Especially in office buildings:
Some areas may be unoccupied.
Different exposures have staggered loads.
Internal gains vary by floor/time of day.
You install chillers with a total capacity of 1160 TR. This is based on simultaneous peak demand.
FCUs connected may require 1450 TR ร 2.4 GPM/TR = 3480 GPM total (connected). But chiller will supply only 1160 TR ร 2.4 = 2784 GPM.
Use 2-way valves on FCUs (Variable Flow System):
Only FCUs that need cooling will get water.
Flow adjusts dynamically via differential pressure sensor and VFD pumps.
Balancing valves, or PICVs (Pressure Independent Control Valves), help regulate flow.
Use differential pressure controllers to ensure that when many FCUs are partly loaded, the system doesnโt over-pressurize and misbehave.
So balance the system based on connected flow, but pump the system only for the actual load demand.
Hi Kiran,
In extent to the above sharing, I would add that all FCUs should be tested to their design flow rate. If all FCUs are ON at the same time, you may not get full flow due to diversity design. Hence, group them as per your design basis for diversity and test them in groups. That way, you ensure all FCUs can meet their designed flow and the chillers can be tested to full load.
Thanks.