The DU144 straight automatic bypass valve controls the water flow in the heating circuit, to maintain a minimum flow rate while the boiler is fired. The boiler return temperature is raised and this reduces the corrosion caused by flue gas condensation. In addition, when radiator valves are closed it also maintains flow over the temperature sensor on the boiler to ensure proper operation of external temperature compensating controls. On gas fired water heaters it guarantees a minimum flow circulation when thermostats or radiator valves are closed.
 
To install a Honeywell DU144 automatic bypass valve, first install it in the bypass circuit between the boiler's supply and return pipes, ensuring the water flows in the direction of the arrow on the valve body. Next, commission the heating system and determine the pump speed and boiler's minimum flow rate. Finally, use a pump curve and the DU144 setting chart to calculate the correct pressure setting and adjust the valve's handle to match the setting.