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Boiler Bypass and Layout

ShadowdocShadowdoc Member Posts: 20
edited October 2016 in Plumbing
Attached is my heating system layout. Boiler is a Teledyne JVT100NDI (133,000).
Confused about the piping and bypass setup. Bypass pipe is much shorter than in diagram with no valve to regulate (see pic)

3 Circulating pumps (CP).

I think CP3 has to do with the bypass to maintain return temp, but when CP3 runs, it seems to draw heat through the entire system, even when a floor has no call for heat.

2 story older home. About 1800 sq ft split evenly between 2 stories. Mostly PEX piped. There about 200 linear feet of PEX running along the unheated basement ceiling for supply and return. I foam sleeve insulated it all.

I was told I just cut out CP3 and the bypass and straight pipe the return. Boiler manual indicates a need for the bypass to maintain return temp.

Is this setup correct as it is? Thanks in advance.


  • ShadowdocShadowdoc Member Posts: 20
  • ShadowdocShadowdoc Member Posts: 20
    There are no flow control valves, which surprised me when I bought the house. I thought that may have been the reason there was flow through a zone even if there was no call for heat when CP3 ran.

    I'll install the 2 Flow control valves and remove CP3 and the bypass.

    That's essentially what I have at my other house but I wasn't sure.

    Thanks so much for the input. Really appreciate it! Stay warm.

  • gennadygennady Member Posts: 802
    You cannot remove c3 pump, c3 pump assures proper flow through heat exchanger. Whole setup is primitive primary/secondary arrangement.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • ShadowdocShadowdoc Member Posts: 20
    And the bypass? Seems like most of the heat is just being recirculated at the boiler and less is being sent through the system.

    Is there a better setup to have more heat in the system?

    Would installing control valves help?
  • ZmanZman Member Posts: 6,037
    Your boiler is a copper fin. For that reason you need to maintain constant flow. That is why the boiler circ and bypass is installed.

    Unfortunately the installer did not understand primary/secondary piping and your boiler circ is ghosting water though both zones. I don't think a flow check will solve your problem.

    The right way to fix this is to repipe the whole thing correctly. Putting a zone valve on each zone would be the simplest fix.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rodhot_rod Member Posts: 13,893
    Those copper boilers like to have a dedicated circulator, as Gennady mentioned. Primary secondary or a buffer is the best way to pipe them.

    If you zone pump them, be sure the pump(s) supplies adequate flow, the bypass helps assure that.

    It seems grossly oversized which will lead to short cycling.

    Do a heat load calc and measure how many feet of fin tube connected.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ShadowdocShadowdoc Member Posts: 20
    Thanks for everyone's help. The tech that came to start up the system wanted to remove the CP3 and bypass. I read through the Boiler manual and figured it wasn't the right thing to do.

    I plan on running it as is for now and see how the winter goes.

    I'll try to find and more informed tech if I feel the heat is not adequate.

    I can do all the work (install), just not sure of the schematics and placement of everything.

    Thanks again for the dialogue

  • ShadowdocShadowdoc Member Posts: 20
    Bought the house this way.
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