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Dan C.
Dan C. Member Posts: 248
How would I calculate how far I can run and how much radiation I can put on a monoflow branch. It is a second floor bedroom. They are putting back the same radiator that came out plus adding 3' of cast iron baseboard. Now they want to add another radiator on the opposite end of the room. I'm not sure if it will be able to handle it but I don't know gow to figure that out. It is a 1" main with a 1x1/2 monoflow on the return and a 1x1/2 regular tee on the supply.


  • Ironman
    Ironman Member Posts: 6,868
    edited October 2017
    I definitely would NOT attempt to add a second radiator onto the existing mono flow branch.

    If you're unable to run another branch from the main to upstairs, then you could add a circulator to the branch and pipe it primary/secondary. Then you could split the branch upstairs to more rad's.

    Like this:

    The Tees should be within 12"or less of each other and be regular Tees, not Monoflo. Put the circulator on the secondary supply riser. The flow is from left to right in the main in the diagram.

    Here's a good article on Monoflo systems:

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    EBEBRATT-Ed Member Posts: 11,989
    We need to know the heating load on the three pieces of radiation.

    1/2" copper is good for 1.5 gpm or about 15.000 btu/hr. That's best case even with a circulator added as @Ironman mentioned.

    If 1/2" will carry the heat you need install a circ pump and remove the monoflow tee.

    I wouldn't try and pipe this as a monoflow branch ..........probably won't work
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,449
    I have......cough.....cough.... put 30' of 3/4 baseboard on a monoflo 1x1x3/4" with diverter T on return only. Been operational for 20+ years, with less than 5 degree drop across the baseboard run. Original diverter loop has the two T's 6" apart. I did it to see if it would work before I actually piped it correctly. 1" loop has 10 monoflo loops driven by 0010 on the return... I didn't do that part!

    Flame suit ready....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    EBEBRATT-Ed Member Posts: 11,989
    @Solid_Fuel_Man , he only has 1/2" lines. We don't know the load he is putting in and I would rather not guess. Others are free to suggest what they would do.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,449
    I understand, I was just speaking from what I've seen actually work on a monoflo system. Seems they are more robust than some believe. Just not fun to bleed.....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!