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Making the best with less than perfect

PaulVW Member Posts: 2
We will be replacing a boiler with 2 high efficiency boilers because of how the mechanical room is piped, we can't change the 9 zone pumps to pump away from the expansion tank. The pumps will be on the return to a 3" hydrolic separator. Normally I connect the expansion tank on or near the hydro-separator. I'm wondering if in this case it would be preferable to install it on the boiler side of the hydro-separator? All the pumps are fairly low head and the zone pipes are good sized so I don't anticipate any problems with cavitation or air removal as the existing system worked reasonably well for many years. Would like some ideas to make the best of a less than perfect situation.


  • Steve Minnich
    Steve Minnich Member Posts: 2,696
    I agree with Paul. The near boiler piping is every bit as important, if not more, as the boiler itself.
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
  • SWEI
    SWEI Member Posts: 7,356
    Starting with the near-kilowatt load of all those circulators...
  • hot_rod
    hot_rod Member Posts: 15,378
    edited July 2016
    What about changing the pumps to zone valves and then use an ECM system circ?

    It is not recommended pumping into the return on a sep or primary secondary piping.

    With multiple boilers and large piping, if the system requires a base mounted expansion tank, of example, you can connect the tank like this.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    SWEIPaul S_3