Nathan, You are correct that elevating the recirc temperature to 140F is used to manage Legionella bacteria. It is a process called Thermal Disinfection. Thermal Disinfection requires safety devices at each fixture and a way to manage and confirm the process. Your normal recirc temperature will be whatever the tank is set for or the temperature of the master mixing valve minus system heat loss. It needs to be maintained at a safe temperature to prevent scalding. You can elevate the hot water and recirc temperature if you have point of use mixing valves at each fixture to protect the end user.
Nathan, You are correct that elevating the recirc temperature to 140F is used to manage Legionella bacteria. It is a process called Thermal Disinfection. Thermal Disinfection requires safety devices at each fixture and a way to manage and confirm the process. Your normal recirc temperature will be whatever the tank is set for or the temperature of the master mixing valve minus system heat loss. It needs to be maintained at a safe temperature to prevent scalding. You can elevate the hot water and recirc temperature if you have point of use mixing valves at each fixture to protect the end user.