This piping would allow one variable speed controller to protect either boiler. The control targets the tank temperature ay say 180 °F . If the sensor on the return pipe see 140 °F or lower it slows the injection pump. I've used this exact injection mixing on large multi boiler radiant systems with multiple cast iron boilers.
The hydro separator assures the boiler get adequate flow regardless of the injection flow. The boilers could have different sized pumps, if needed, as only one or the other would fire, not both at once.
Some of the tekmar controllers could run this arrangement and even fire the oil boiler, as backup if the temperature drops to a set point.
The loads would take off additional taps on the tank.
In this drawing the oil boiler feeds the tank, a 3 way zone valve could be used so the oil only heats the load directly. Some buffer is nice, however if you have multiple loads, it keeps the oil or other boiler from short cycling.
Thanks to Siggy for the design idea.
hr
The hydro separator assures the boiler get adequate flow regardless of the injection flow. The boilers could have different sized pumps, if needed, as only one or the other would fire, not both at once.
Some of the tekmar controllers could run this arrangement and even fire the oil boiler, as backup if the temperature drops to a set point.
The loads would take off additional taps on the tank.
In this drawing the oil boiler feeds the tank, a 3 way zone valve could be used so the oil only heats the load directly. Some buffer is nice, however if you have multiple loads, it keeps the oil or other boiler from short cycling.
Thanks to Siggy for the design idea.
hr
![[Hearth.com] another boiler piping concept](/talk/data/attachments/22/22636-37434dd3a9399b41ba961fe72706a3d8.jpg?hash=6FGy_PWzd0)
