Floor heat pump deadhead

[rickdavis]

I’m finally getting around to hooking up my owb to my 3 zones of floor heat in my house and garage. I’ll have a mixing valve installed before the circulator pumps to lower the temp to 120 and one further up line to keep the return water above 140 deg. My question is will the 140 deg mixing valve let enough water go back to the boiler if my floor heat is not calling for any water flow or is my supply pump going to deadhead?

 

[E Yoder]

I think you'll need to sketch a diagram of your piping layout and where the mixing valves and pumps are located for me to give an accurate answer.