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monoflo or two pipe

able Member Posts: 16
Yes this sounds good to me to control would you run constant circ off outdoor reset with trv's and presure bypass valve or how did you guys control youre systems.Thanks again for the input


  • able
    able Member Posts: 16
    cast iron baseboard

    I recently looked at a job with a old boiler and cast iron baseboard I am going to replace boiler add a indirect I will be using a biassi 3 pass boiler oil my problem is the piping of the system someone decided to repipe system because some rooms were not heating some one ran new piping and made it a split loop system but there are still some old monoflo tees installed .I plan on totaly repiping system but dont know if I should divide system in half and zone them as separate loops or make it a two pipe system or a monoflo system again I would think zoning the bed rooms as one zone and the living room and kitchen and bath as another zone would be the most cost effective but I dont know the pressure drop trough the old baseboard would it work okay as a loop system or should I pipe it differently.thanks for the input
  • Brad White
    Brad White Member Posts: 2,398
    One idea (none of the above)

    If you can salvage the existing branch run-outs (copper or iron pipe, whatever, but terminated where you can get to them), you could run Pex-Al-Pex home-runs back to a manifold or manifolds depending on your logistics.

    The manifolds would be fed by either new or existing piping, but could be short "wholesale" runs to manifolds serving the "retail" side of things.

    This could save significant piping cost and allow you to give individual control to each radiator much as a TRV would. Many manifolds can accept motor actuators (to room thermostats) but even without these, you can balance each room individually.

    Might this work for you?
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    I second Brads...

    idea. That is whay I did at my home w/ panal rads and have done other places. Much simpler and cleaner... home runs are VERY easy to snake around walls...kpc

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  • Brad White
    Brad White Member Posts: 2,398
    Several choices

    but given that you are replacing the boiler anyway (and it is oil-fired with limited turn-down range), this is what I would do:

    1) Set up boiler with it's own loop on outdoor reset. Range from say 180F (whatever your highest need is) down to 130 to 140 F. or whatever low temperature you can tolerate so that you stay above dewpoint on the return water side.

    The domestic indirect will be a direct circulator off of this boiler loop by the way.

    2) Set up a secondary circuit to feed the radiator manifolds. This can be in the form of:

    A. Manifolds with built-in mixing valves and circulators with outdoor reset. Allows each manifold to have a different temperature this way too, if you are using more than one.

    B. Separate single loop to feed manifold(s), either by 4-way mixing valve or injection.

    Either of these last two will allow deep reset, from full boiler temperature down to near room temperature water. Nearly perfect linear control.

    The one you choose will be up to you, to suit your installation conditions, number of manifolds and number of different temperatures actually required.

    From there you can fine tune the rooms with control valve heads -if you really need to.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
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