Boiler protection mixing valve

mike chacon

I have a cast iron boiler adding a caleffi 280 mixing valve for boiler protection. I will move my pump to return side, pumping into boiler with mixing valve on inlet side of pump. Can I also add my expansion tank on inlet side of pump, between inlet side of pump and after mixing valve. Trying to avoid adding another pump in a primary/ secondary situation.

Gordan

Why?

Why move the circulator? It should be fine where it is. It will not make a whit of difference to the mixing valve, and it's better for air eliminator to be between the boiler supply and the circulator inlet.

SWEI

boiler circ location

Caleffi does show them piped this way on all their drawings, and the 281 also has its pump in the same location.  I'm wondering if they have a reason for this?  HR?

Gordan

I could see for the 281

That's packaged so tightly that the turbulent post-circ flow might adversely impact the mixing valve's function.

mike chacon

Boiler protection

Is it possible to use caleffi 280 mixing valve without piping it into a primary/secondary strategy. I'm trying to avoid second pump.

SWEI

one pump

will work (mostly) if your distribution system is designed for the temp the boiler runs at. 



Much better to run separate boiler and distribution circs with a properly sized buffer tank, and a motorized mixing valve and outdoor reset control.

mike chacon

Boiler protection

My only concern is keeping 140 degree water going back to boiler. I have a cast iron boiler and heavy cast iron radiators in a one temperature system. Looking at caleffi diagram for the 280 mixing valve is confusing. It has you pumping into expansion tank.