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Radiator won't heat - help!

David Moseley
David Moseley Member Posts: 7
Have a hot water system (radiators), converted from 2-pipe steam many years ago. Small 2 story house, about 2400 sq ft, 9 radiators total. Has a Glowcore condensing boiler installed by someone else several years ago when system converted to forced hot water.

There is one radiator upstairs that will not heat. It happens to be the last radiator off the main (if this matters). All other radiators heat fine. The radiator valve is open, the return ell is OK (no restriction/blockage). Water pressure is adequate. Supply risers tie in at bottom of all radiators. Disconnected radiator, can see through from one end to the other of the radiator. Put ball valves on supply and return. Individually open each one and get water. When put all back together, water will not circulate through the radiatior. When bleed radiator, hot water comes up the return, that line gets hot. Supply side is cold. Can not figure this out. Any ideas?  

David Moseley 


  • Big Ed_4
    Big Ed_4 Member Posts: 1,646
    Parellel System

    Last one on the line ? The last supply and the last return ? If so you may need to throttle down the other radiators on that main line .Which kinda sucks getting the right setting.. Pressure drop decreases at each set of radiator risers .. Pressure drop is needed for water flow ...

    A much better set up is reverse return , First radiator on supply would be the last return . This set up will help equalize pressure drops and resistance along the branches of radiators .. Would entail piping a new return from the end of the line ...
    I have enough experience to know , that I dont know it all
  • David Moseley
    David Moseley Member Posts: 7
    Reply to Ed

    In this system, last supply is first return (reverse return). I understand that you need pressure drop for the water to move. The radiator directly below this one heats fine and you can see the supply and return connections to the main are about 12" apart from the ones for the radiator that doesn't heat. I also shut off the valves to all but 4 radiators (because some of the valves will not move;stuck open), and still get no flow through this radiator.
  • JStar
    JStar Member Posts: 2,752

    Can you get pictures of where the radiator piping tees into the supply and return main, and of the radiator?
  • David Moseley
    David Moseley Member Posts: 7

    Yes, I will get pictures and post them (assuming I can figure out how to upload them to the site). It will be in morning before I can do this. Be on the look-out for them; I need to solve this SAP. This house has been sold, and clsoing is next Thursday. A home inspector found this radiator not heating.   
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,166
    may be it would be faster to call a pro in?

    If you check the list there may be someone close to you?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • David Moseley
    David Moseley Member Posts: 7
    radiator won't heat

    I believe we located the problem, through trial and error. Found a second circulator in the crawl space wired in parallel with the main circulator. This circulator was apparently installed to improve circulation through 2 kickspace heaters in the kitchen. These kickspace heaters are fed off the main before the radiator I was having trouble with. Disconnected this circulator and voila! the radiator starts heating. I'm not quite the expert, but apparently this second circulator when operating is creating enough of a pressure change downstream between supply and return that there was insufficient delta P across the radiator for the water to circulate. Ed mentioned this in a previous post. Thanks Ed, your comment got me thinking and to keep looking deeper into the problem. Funny thing is the the 2 kickspace heaters in the kitchen seem to work fine without the need for this second circulator     

    David Moseley
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