A buffer tank is an additional reservoir that increases the total volume of water in chilled water circuits, thus preventing short circuits in the chiller or heat pump and dampening variations in flow and temperature. In circuits separated by a heat exchanger, it provides hydraulic regulation of the system, smoothing out flow and temperature variations on either side of the exchanger, which improves efficiency, extends the service life of compressors and pumps, and results in more stable indoor conditions.

It is widely used in cooling systems operating with fan coil units, air handling units (AHUs), and industrial cooling circuits in homes, hotels, shopping centers, offices, and industrial facilities. It solves common problems such as frequent starts at low load, supply air temperature spikes during sudden increases in consumption, reduced temperature difference (ΔT), and erroneous sensor readings. In solar and heat pump solutions, it also improves system efficiency by temporarily balancing production on the source side and consumption on the demand side.

While baffle-free tanks are sufficient for simple hydraulic balancing and volumetric expansion, baffle-equipped tanks direct the flow within the tank, thus reducing mixing. This maintains stratification between the feed and return, improving temperature stability. Baffle-equipped tanks are preferred for projects with significant field flow fluctuations, frequent and abrupt emptying, or where precise feed temperature control is required. In standard applications where space and cost are more critical factors, baffle-free tanks offer an economical and efficient solution.

Cooling circuits typically use carbon steel casings and are equipped with internal linings or a suitable water treatment system to protect them against corrosion. In systems using glycol, the chemical compatibility of the lining and seals must be verified. Closed-cell, vapor-difference-resistant insulation and a continuous vapor barrier are essential to prevent condensation on surfaces below the dew point; otherwise, heat loss and corrosion of external surfaces will increase. The operating pressure, connection diameters, and flange locations must be selected according to project standards, and additional fittings for drainage, safety, air venting, and detection nozzles should be provided as required.

The reservoir is typically positioned on the chiller return line to maintain a stable temperature at the evaporator inlet. While the supply line is sometimes preferred, the goal is to ensure accurate and continuous sensor readings, as well as stable pump circuit operation. An automatic air vent valve at the top, a drain valve at the bottom for complete drainage, suitable mounting brackets, and vibration dampers should be installed. Temperature sensors should be positioned at heights that accurately represent stratification. Circuit filters and a periodic inspection plan should be implemented to prevent sediment and sludge buildup. The integrity of the insulation and vapor barrier should be checked periodically.