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you will go with one-pipe monoflo setting or two-pipe reverse return setting?

heatingFunheatingFun Member Posts: 84
Finally I am ready to call in plumbers for their quotes on my gas hot water heating system upgrade. It is a big job with some of new CI baseboards being added and add a new zone for the unfinished basement (framing is in progress).

The attached pdf file is my 3 yrs old Alphine gas boiler's setting. There is a separated boiler circulator. Is this setting a primary/secondary setting (just curious)?

Another attachement is my house floor layout drawing and the existing heating pipe setting.

My house is a ranch house. First floor has a big family room need to be added into the water heating system. A new zone for full basement will also need to be added into the water heating system. The existing main pipe is 1" pipe. All baseboards are and will be CI.

If you were me, you will go with one-pipe monoflo or two-pipe reverse return?


  • EricEric Member Posts: 261
    I think....

    if you plan on using the existing piping, the reverse return will be easier and cost less than adding mono flow tees.
  • icesailoricesailor Member Posts: 7,265

    Where did you get that PDF? Most of us wouldn't mount the expansion tank on the secondary side where you can shut off both secondary side valves and isolate the boiler from the expansion control.

    On the second drawing, it always has part cut off on my computer but it looks like you have (or someone has) drawn it with a two pipe direct return. Direct Returns are considered by most as a bad practice. If your intent is a Two Pipe reverse Return, that isn't one. Parallel Reverse Return = First In, Last back. Direct Return= First in, first back, last in, last back. A properly installed reverse return will almost always have a place where there are three pipes in parallel where a direct return will not.
  • jonny88jonny88 Member Posts: 1,139

    Why out of curiousity are you going with an Alpine
  • heatingFunheatingFun Member Posts: 84

    I have the Alphine gas boiler now.
  • heatingFunheatingFun Member Posts: 84
    edited August 2014
    Icesailer, you are really an expert

    I have two versions of the boiler installation guide. I just uploaded the wrong one. After checked with my installation, this one is the actual boiler side setting I have now.
  • icesailoricesailor Member Posts: 7,265
    Expansion Tanks:

    The Expansion Tank is still on the secondary side where in my opinion, it should be on the primary side.

    Others may not agree but I consider that piping scheme a hybrid P/S piping. There's something about how the primary loop connects and the two secondary loops connect at either end that makes me think that if it didn't work properly, and I was called to look at it as to why, I would blame it on that connection. The idea of primary/secondary is that you have whatever flow through the primary loop and then secondary flows that create their own little bit of happiness inside the primary. That's why the closely spaced tees need to be as close together as you can reasonably get them. Too far away and the flow can collapse. How it is drawn and how it is installed are different. But of it is drawn in a way that bad, it might be a problem. I always have a gut feeling about running things through tees like drawn.

    But again, if you shut off those two isolation valves on the primary side, with the expansion device on the secondary side, you have to expansion protection on the boiler.

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