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Injection pumping?

mattyc Member Posts: 44
I have a customer with an oil fired cast iron boiler with a two zone fin tube baseboard hydronic system running a tankless coil for HW...for a basic system it works fine except the cx is not used to the expansion/contraction noise of the baseboard when the cold pipe heats up and rubs against every joist in the house.(for me it's a normal sound but in this house it is a bit more extreme then usual) opening up walls to relocate pipe and insulate and clamp properly is not an option. I was thinking about maybe using injection pumping with outdoor reset to hopefully keep the pipe running lower temps for most the year and not have extremes temp changes..thinking maybe keep the zone pump to run constant during design temps and the injection and boiler pump to run on call for heat. Curious if this would solve the noise complaint or if anyone had any other suggestions not including opening sheetrock


  • Jamie Hall
    Jamie Hall Member Posts: 23,526
    This almost certainly can be repiped as a primary/secondary system. The secondary would run all the time, with the temperature controlled with a mixing valve or other control, controlled by outdoor reset, and the boiler supplying heat when needed. Lots of ways to do it -- and there is at least one good book on the subject, available from the store on this site.

    A very common and normal arrangement...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 7,385
    A lot of the noise may be from within the BBs if there's no room for lineal expansion. I'd carefully evaluate each one first then look at an injection control like the Tekmar 356.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,588
    Depending on your setup, a mixing valve may be a better option than injection mixing. Injection mixing tends to be a bit of a challenge to get dialed in. If you do injection mixing, tekmar has a good white paper on proper piping. be sure to put a balancing valve on the mixing loop.

    The taco I series valve is a good option for a mixing valve.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 22,330
    it may require some boiler re piping to add an injection mixing system, either primary secondary or a hydraulic separator. It will also require an additional circ pump

    Injection mixing is not as popular as other methods, anymore Various mixing valve options are the more common method
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream