Chilled Water Buffer Tanks?
Chilled Water Buffer Tanks?
(OP)
General question regarding buffer tanks for chilled water systems.
I have a primary-secondary system with two 70 ton air-cooled screw chillers. My total system volume is approximately 950 gals. The system is mainly serving fan coils units with 2-way modulating valves. Do I need a buffer tank?
Cemline recommends a minimum sys volume of 3-6 gallons/ton. I have 6.7 gallons per ton, so I think I'm okay. However, another engineer in our office said that I should only consider the volume in the primary loop, not the total system volume? Is this correct?
Also, since a screw chiller can modulate continously throughout its operating range, does this lessen the need for a buffer tank.
Any thoughts?
Thanks in advance.
I have a primary-secondary system with two 70 ton air-cooled screw chillers. My total system volume is approximately 950 gals. The system is mainly serving fan coils units with 2-way modulating valves. Do I need a buffer tank?
Cemline recommends a minimum sys volume of 3-6 gallons/ton. I have 6.7 gallons per ton, so I think I'm okay. However, another engineer in our office said that I should only consider the volume in the primary loop, not the total system volume? Is this correct?
Also, since a screw chiller can modulate continously throughout its operating range, does this lessen the need for a buffer tank.
Any thoughts?
Thanks in advance.





RE: Chilled Water Buffer Tanks?
Soooo, you can either increase your primary chw header size (to a point), add a buffer tank as you say, or solve the problem with the controls - ensure that your controls start the screw chillers on low load and/or start the secondary circulation before starting the chillers.
RE: Chilled Water Buffer Tanks?
---KenRad
RE: Chilled Water Buffer Tanks?
The chillers will not be operating unless the secondary pumps are on, so the "system" volume should be the entire secondary system as well as the primary.
Thanks for your help.