Fewer Circulators with 3-way diverter valve

optimist55116

I am adding an indirect water heater to my hydronic heating system and updating the design a little. In the process, I am trying to reduce the number of circulators.  In the typical drawings of a system with a non-condensing boiler, a buffer tank, and an indirect, each has its own circulator pump.  Couldn't  I eliminate two of these pumps with a 3-way mixing/diverter valve (motorized).  Assume that the indirect gets the full attention of the boiler when calling. The following is a sketch of what I am thinking (with many non-relevant components not drawn here):



    

hot_rod

Sure

As long as has adequate Cv for the load. What size boiler?

optimist55116

Thanks and ...

Cv is around 20 and boiler takes in 130K (so about 100K) out.  I

hot_rod

The few I have done

We're 80K boilers. I put the zone valve on the return piping. Cooler temperature and less delta P. I used a common paddle style, spring return ZV with a 7.5 Cv 1" size