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

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by lmei007, Aug 24, 2014.

  1. lmei007

    lmei007 Member

    Messages:
    167
    Location:
    Maryland
    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?

    Attached Files:

  2. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    If it were me I would rip out all the baseboard and go with wall hung steel radiators. What you have there isn't enough radiation to allow the boiler to properly and efficiently condense. As for piping, monoflow is expensive and so is reverse return with little or no real benefit on a job that size.
    lmei007 likes this.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,686
    Location:
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    Monoflow is perfectly adequate UNLESS you intend to install valves in each room and possibly turn off the radiation in some rooms.
  4. lmei007

    lmei007 Member

    Messages:
    167
    Location:
    Maryland
    No idea about the wall hung steel radiators. The first time heard this. must be expensive. All my CI baseboards are ready to go. That new radiator will be an option for my next new house if any.

    You mean the boiler is too powerful and the number of baseboards isn't big enough for the boiler?

    So the reverse return will still work properly in this job size?
  5. lmei007

    lmei007 Member

    Messages:
    167
    Location:
    Maryland
    Are you saying you will choose reverse return then?
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    I'd just loop the whole thing, in and out.

    Your boiler is designed to operate at maximum efficiency only if it can actually run at temperatures that allow it to condense. For it to condense the delta T, or difference between the output and the return must be such that it is within the operating parameters for your equipment. When there is not enough emitters, or "radiation" the return water temperature comes back too high which keeps the boiler from operating efficiently which is why if you keep your baseboard and want the unit to run at its best performance curve, a straight up loop system is probably your best option but, ideally you should have done a manual J heat loss on the house and matched the boiler and radiation to the BTU/hr heat loss of the envelope.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,686
    Location:
    Cave Creek, Arizona
    A reverser return is NOT affected by the loss of flow when you turn off radiators, but a MonoFlo is severely affected if you do it.
  8. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine

    That depends on where the shut off is installed. If it's installed at the radiator no water flows from the main so you actually pick up some velocity because there is no downstream turbulence as the water flowing through the radiator meets back up with the main.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,686
    Location:
    Cave Creek, Arizona
    The velocity increases, but the volume is reduced because the only flow is what goes through the venturi. With the valve open, the water circulates through the radiator and is returned to the main maintaining full flow.
  10. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    Yes, with the radiator valve closed no water flows through the radiator and flow is only slightly effected.
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