Designed to protect non-condensing boilers from flue gas condensation, when installed properly the 280 Series ThermoProtec mixing valve and the 281 Series ThermoBloc mixing valve/pump distribution units will maintain a minimum boiler return temperature to prevent condensation of water vapor in the combustion gases. This condensation will not only damage gas fired boilers but will result in tar deposits and create dangerously flammable situations in wood fired and biomass boilers.
These boiler protection valves come with a preset thermostatic sensor cartridge. Standard models include either a 130°F or 140°F cartridge and Caleffi also offers 115°F and 160°F cartridges, available separately, for special applications. This cartridge controls the minimum return water temperature by mixing the heated supply fluid with the load return. When the boiler return temperature is below the cartridge setpoint, the mixing valve will be in full bypass position (no flow to the load) to bring the boiler return up to temperature as quickly as possible. Once the setpoint is reached, the mixing valve will start to open to the load return. The mixing valve will be in full flow to the load (no bypass) at 18°F above the cartridge setpoint.
We’ve had a few technical calls about changing the cartridge to better suit the application; this quick video featuring Cody Mack will explain how to do just that!