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replace boiler

scooter Member Posts: 1
I am considering replacing my old boiler, and am wondering if I can connect a new high efficiency unit( a triangle tube prestige perhaps) to my old( built in 1900) gravity hot water system.I have the old cast iron radiaters and don't want to give them up. My installer is afraid these new boilers may not work because of the vollume of water in the system.


  • Tim McElwain
    Tim McElwain Member Posts: 4,555
    Do you have

    a circulator on this sytem now? Or is it still a full gravity system?
  • John Ruhnke
    John Ruhnke Member Posts: 882

    Those old gravity fed hot water heating systems are the perfect candidate for a mod/con boiler. Most of the time those radiators are over sized. So you can run very low water temps. This increases the efficiency of the mod/con boiler. If done right it will cut your fuel bills in half!!!!!!!!!!!!!!!!!

    The best thing to do is to replace the radiator valves with thermostatic radiator valves. The flow characteristics will change when adding a pump and you might get uneven heating. Not so with the thermostatic radiator valves. They will balance everything out.
    I am the walking Deadman
    Hydronics Designer
    Hydronics is the most comfortable and energy efficient HVAC system.
  • kcopp
    kcopp Member Posts: 4,091
    if your installer....

    is not comfortable w/ this set up you should keep looking. Mod-cons are a perfect candidate for your set up.... run the syetm off a Grundfos  Alpha type pump and TRV for each radiator... perfect.
  • John326
    John326 Member Posts: 1
    Boiler sizing

    I have an old gas hot water boiler that needs replacing. How do I know the contractors are sizing it correctly. I have all radiators throughout my home. Thanks
  • Tim McElwain
    Tim McElwain Member Posts: 4,555
    Have them do a heat

    loss first, Then determine the feet of radiation you have, the boiler output wants to match to the radiation and heat loss of the house.

    If you are going to use a Mod/Con system they should spec for outdoor reset and determine also if they can run at lower design  outlet temperatures. That way they are using the mass of the radiators to give you proper heat and getting low enough return temperatures for condensing.
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