All About Chilled Water Buffer Tanks!

     American Wheatley HVAC’s Chilled Water Buffer Tank (CBT) are designed to be used with chillers that do not have significant water volumes of sufficient size in relation to the chiller.

     An insufficiently sized system does not have enough of a buffer capacity for the chilled water causing poor temperature control, erratic system operation, and extensive excessive compressor cycling. 

     With our HVAC Chilled Water Buffer Tank, these problems can easily be avoided.

     Our CBT adds water to the buffer system and reduces the rate of change of the returned water. With a properly sized CBT tank, your system will run smoothly without a hitch.

     We are here to answer all your questions about our Chilled Water Buffer Tank!


What does a Chilled Water Buffer Tank do? 

In short, the Chilled Water Buffer Tank adds the necessary volume to "buffer" a system with low water volume.

A unit's water volume is based upon certain requirements; for example, a typical air conditioning unit requires 3 to 6 gallons per ton of water. A properly sized and installed chiller system will prevent the chiller compressor from short cycling.

Without proper system water volume, the source temperature will be reached quickly and the compressor will shut off. Many chiller compressors can only start 3 times per hour; if the compressor is off when there is a demand for chilled water, the demand cannot be met because the compressor cannot turn back on. You can imagine this would cause very unsatisfied people within the building who cannot have the required cooling!

Buffer-Tanks2-418w Graph

American Wheatley Chilled Water Buffer Tanks are designed for water systems with insufficient water volume capacity, in relation to the chiller capacity. Relatively low water volume systems require additional “buffer” capacity.


  • Constructed in accordance with ASME Section VIII, Division 1, Latest Edition
  • Carbon Steel Construction
  • Maximum Temperature 450°F Intermittent
  • Design Pressure 125PSI
  • Primed Exterior

Optional Features:

  • Manway Handhole
  • Higher pressures
  • Stainless Steel Construction
  • Upper Mounted System Connections
  • External Coatings
  • Insulation / Jacketing*
    *When adding insulation overall tank height and flangeheight (A) will increase based on insulation level, up to 2".

Typical Specifications:

Furnish and install as shown on plans our Chilled Water Buffer Tank as manufactured by American Wheatley HVAC Products. The tank shall incorporate a baffle to promote tank water storage temperature stratifica­tion. The system water connections must be in inches (NPT/flanged/grooved).

Chilled Water Buffer Tank Chart

The tank must be constructed in accordance with the most recent addition of Section VIII of the ASME Boiler and Pressure Vessel Code. Each Chilled Water Buffer Tank shall be American Wheatley Model AWCBT.

How do I size a water buffer tank?

Chilled Water Buffer Tank diagram

Chiller manufacturers recommend that somewhere between two to six gallons per ton for nominal cooling in a typical system. Even higher, six to ten gallons when temperature accuracy is critical.

To calulcate what size Chilled Water Buffer Tank that you need, use the following formula.


For clarification, refer to the instructions below.



Determine the system volume required by the manufacturer. Remember to check with the manufacturer for their recommendations as to how many gallons they suggest per ton.

SVR = System Volume Required = Total chiller tons X manufacturer-recommended system volume required per ton



Calculate the actual existing volume of piping and equipment Table A, below indicate gallons per linear foot of schedule 40 pipe.

ASV = Piping Volume (PV) + equipment volume (EV) gallons



Calculate actual Buffer Tank size required (CBTR)

Deduct the actual system volume (ASV) from the System Volume Required (SVR).



Chilled Water Buffer Tank Sizes

Refer to American Wheatley AWCBT Charts for standard sizes. Larger size are available POA.

How are Chilled Tanks Installed?

American Wheatley Chilled Water Buffer Tanks are typically installed to ensure adequate water volume along with decoupling and mixing action necessary with today's primary-secondary systems.  All steel tanks manufactured by the American Wheatley HVAC Products are constructed in accordance with the best commercial practices. The ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 (an American National Standard published by the American Society of Mechanical Engineers) provides rules for the construction of pressure vessels.

This includes requirements for materials, design, fabrication, examination, inspection, and marking. All steel tanks constructed in accordance with all of the applicable rules of the Code are identified with the official Code Symbol Stamp on the vessel nameplate. All steel tanks that include the Code U stamp will also include a National Board Number and registration with the National Board of Boiler and Pressure Vessel Inspectors.

Of course, these are just a few examples of what we have to offer. We will be more than happy to help problem-solve and find you the correct buffer tank that fits your needs. Don’t hesitate to reach out to us today for more information and other buffer tank varieties!