HVAC Tanks

The Wheatley hot water buffer tank (HS) is designed to be used with today's low mass, high efficiency boiler systems. The Wheatley HS series hot water buffer tank affords the needed volume and thermal mass to negate or minimize short cycling during no load or low load conditions. 

Chiller manufactures recommend somewhere between 2-6 gallons per ton for nominal cooling in a typical system. Even higher, 6-10 gallons when temperature accuracy is critical. 

1. Sizing
   • 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
     • SVR = Total chiller tons X manufactured recommended system volume required per ton.  
2. Calculate actual existing volume of piping and equipment Table A, below indicates gallons per linear foot schedule 40 pipe.
   • ASV = Piping volume (PV) + equipment volume (EV) gallons 
3. Calculate actual Buffer Tank size required (CBTR) . Deduct the actual system volume (ASV) from the System Volume Required (SVR) CBTR = SVR -ASV 

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

Wheatley 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.  

Check the vessel for signs of damage during shipping and handling. Report any damage for concerns to the factory. Follow safe handling procedures when transporting the tank. Use lifting lugs whenever possible (see figure). Following locally accepted codes and practices for proper mounting and installation. When installing a pressure relief device, verify that the device is set to operate at or below the MAWP of the vessel.

• IMPORTANT: The ASME Boiler and Pressure Vessel Code Section VIII, Div. 1 does not permit any field modification to the pressure vessel after the ASME inspection process is completed. Welding to pressure retaining parts will void the ASME certification. All steel tanks are designed for a specific design pressure. This design pressure is clearly marked on the nameplate as the MAWP (Maximum Allowable Working Pressure). 
• IMPORTANT: It is the responsibility of the user to ensure that the required overpressure protection device is properly installed prior to initial operation.
• IMPORTANT: This product must be installed by a qualified professional. Failure to properly install and periodically inspection and service the vessel may result in serious or fatal personal inquiry and property damage.
• IMPORTANT: All steel tanks must be installed on level surfaces designed to support the total weight of the vessel filled to capacity. Certain states require a minimum clearance of 18" around the vessel (check local codes and requirements prior to installation).
•  IMPORTANT: Failure to properly align, support, and connect interconnected piping will result in leakage and potentially serious or fatal 
• personal injury and property damage. Examine all connections for proper alignment. After start-up, use a leak detector solution to leak check all connections.
• IMPORTANT: Periodically check the interior and exterior of the tank for signs of leakage or corrosion.
• IMPORTANT: Prior to servicing the vessel, insolate it from the system, verify that the system water is at ambient temperature, and release 
• the system pressure. Inspect all gaskets and gasket surfaces. Replace gaskets that show signs of wear or damage. 

FOR MORE INFORMATION  

SAFETY: American Wheatley HVAC flash tanks are designed for systems that require flashing of high pressure condensate into steam for low pressure heating supply mains and to reduce and cool low pressure steam before it is returned to the boiler, condensate receiver, or discharged into sewer. 

INSTALLATION:

1. 1. Visually inspect the tank for possible damage which may have occurred during shipment. If damaged please contact American Wheatley HVAC, Inc. prior to installation at 866-204-5229. 

2. Install flash tank in piping system using the inlet connection (threaded) as an inlet. The opposite (low) side connection will be the outlet. We recommend the installation of a drain valve at the bottom of the vessel for periodic blow down and clean out. 

3. The condensate is discharged through the bottom of the flash tank. When piping flash steam into a low-pressure steam line and discharging condensate directly to a return line, it is important that the condensate has enough of a pressure differential to overcome any back pressure from the return line. Additionally, the placement of a steam trap after the flash tank would be necessary to prevent blow through of steam. If a steam trap is necessary, an inverted bucket trap is suggested. The trap should be sized with a 3:1 safety factor. If back pressure exceeds tank pressure, the use of a reservoir and pumping trap may be necessary to ensure proper drainage. If the flash tank is held at atmospheric pressure, the use of a steam trap on the discharge line would not be necessary since the flash steam is being vented to the atmosphere. The condensate, in this case, would be drained by gravity to a vented receiver which would be placed below the level of the flash tank. 

FOR MORE INFORMATION