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Hot pipes cold rad

SweatyInToronto Member Posts: 75
edited September 2022 in THE MAIN WALL
Have a cast iron floor rad fed by a half inch pipe from ceiling with the return going to the ceiling also. Both pipes are exposed, and are hot but both cool down from 105 to around 85 just 3 to 4 feet above the rad. There is no union or junction visible at that point.

The radiator bleeds water only forcefully but the water temp is tepid! 

The return water to the ceiling starts cold but gets hot further up! 

So the water coming down the pipe is hot. It's cooling down quickly just before the rad. There is water bleeding but it's cold. Make any sense?  Bizarro to me!

No way to remove rad without draining it 300+ gal system or perhaps freezing pipes ... neither attractive options. No shutoffs at all or drain. 

Your thoughts are welcomed greatly!


  • Jamie Hall
    Jamie Hall Member Posts: 23,554
    What type of system is this? It can't be series connected, but is it a monoflow? Or separate supply and return lines up above?

    Has it been this way for some time? Or is this something new -- and if something new, have any changes been made recently?

    You're clearly not getting circulation, but the question of course is why -- and without knowing the system type, it's just guessing.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 9,843
    Is there a valve on the radiator? Is it open?
  • SweatyInToronto
    SweatyInToronto Member Posts: 75
    Thanks for your feedback guys.

    Regarding system it's a 21 unit building, 4 floors built in the 1950s. Don't know beyond that how it's piped, but agree it's not in series.

    There is no shutoff valve on this rad. 

    What's weird is that it seems there is flow, but the water is cold. It bleeds full force which means flow right?   I bled off about half a gal. Should i do more? Water must be coming from somewhere.

    I just don't understand how it can cool off in the pipe over a few feet before it hits the rad.  

    It seems like a good low point for sludge to accumulate, but the loss of heat is perplexing to me. 

  • mattmia2
    mattmia2 Member Posts: 9,843
    Water flowing out the bleeder when you open it does not meant that water is flowing through the radiator, the pressure in the system is simply pushing the water at higher pressure in the system to outside of the radiator which is at a lower pressure. The pipes are heating near the main or mains through convection, water it rising and falling as it changes temperature and heating that section of pipe near the main as well as conduction of heat through the pipe from the main itself. The system should be pushing water through the radiator and it is not. We need to know more about the system to know why. How do you know that there isn't a zone valve at the main?

    You would need to see if you can see where those pipes tie in to the main or mains for us to help you more. My first guess is it is a monoflow system and there isn't enough flow in the main to induce flow in the radiator but that is just a guess, we need more information about what type of system it is.