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Advice would be appreciated

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Maknouf
Maknouf Member Posts: 5
in Radiant Heating

Hi, I was wondering if you guys had any answers or advice to this issue I have. The whole home heats, boiler works fine, pump works fine, system had adequate pressure. Besides this third floor baseboard radiator that is. This radiator does not get hot unless you bleed tons of water (not just air) out of it. The picture with the large cast iron radiator is on the second floor directly below the non-working baseboard. When you feel the pipes rising, the supply is hot and then just becomes ice cold. No movement of water whatsoever. I tried to throttle the ball valve on the third floor to create some type of a pressure difference and force the water to move, but idk. I also added an automatic bleed, but I doubt that will fix the issue. And no, I did not braze those ports; that was a plumber that came prior to me. Also, these two elbows that rise are the peak of this system and directly loop with each other and nothing else about six feet to the right.

IMG_0019.jpeg IMG_0017.jpeg IMG_0015.jpeg

Comments

  • hot_rod
    hot_rod Member Posts: 26,607

    Is there an additional set of tees feeding another radiator behind this?

    Screenshot 2025-12-14 at 9.13.25 AM.png

    You would need to choke down the flow to those radiators also.

    The fintube loop has more flow resistance.

    What is the pressure at the boiler? The boiler is 3 levels or more below the fin tube?

    The fin tube and cast radiators are not a good blend, they heat at much different rates and will never balance properly on one zone.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    MaknoufIntplm.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,605

    As @hot_rod mentioned looks like two tees going through the wall to another rad.

    Balancing may or may not fix this issue.

    The sure fix is to get the baseboard on its own zone or repiping it to be a series loop with the baseboard first on the loop and or replace the baseboard with CI rad.

    Water is taking the path of least resistance and it doesn't want to go to the third floor.

  • Jamie Hall
    Jamie Hall Member Posts: 26,844

    You will need to reduce the flow to any radiators on a lower floor that are on this same loop. Water is lazy, and all that pipe and the fin tube… it's going to go somewhere else unless you force it to go through the fin tube.

    Keep the valves on the fin tube wide open!

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Maknoufbjohnhy
  • Maknouf
    Maknouf Member Posts: 5
    https://forum.heatinghelp.com/discussion/comment/1877243#Comment_1877243

    @hot_rod no the tees are plugged off. Its just that one radiator you see. The boiler pressure is at 15 psi. Id prefer not to raise it but if need be its fine. I just changed the expansion tank and put a much larger one. The boiler is in the basement. Then there is a first second and the copper loop is on the third. So you suggest to throttle the downstairs radiator instead and leave the top floor wide open?

  • Maknouf
    Maknouf Member Posts: 5

    @EBEBRATT-Ed thank you for the response. It is only feeding that radiator on the second floor. Do you mind elaborating on how a repipe on the top floor would go? Instead of replacing it with a radiator. Id truly appreciate your input.

  • Maknouf
    Maknouf Member Posts: 5

    Thank you @Jamie Hall

  • Steamhead
    Steamhead Member Posts: 18,209

    That fin-tube may have just enough internal resistance in it to keep the water from circulating through it when there is an easier path elsewhere. And has anyone looked to see if someone reduced the pipe size where it comes up through the floor and connects to the fin-tube?

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Maknouf
    Maknouf Member Posts: 5

    @Steamhead it maintains the size going up. Upstairs are two elbows by 3/4. Im thinking of taking everyone’s advice and throttling the second floor radiator instead the hopes that it flows upstairs.

  • mattmia2
    mattmia2 Member Posts: 15,634

    does water come out of that schrader that someone used instead of a bleeder?

    a repipe would mean you'd have to get the pipes from the baseboard at least to the mains in the basement if not all the way back to the boiler. even if you do that because the fin tube has so little mass compare to the cast iron it won't heat evenly with the rest of the house. i doubt that it is a big enough load to put on its own zone without running in to short cycling issues. A cast iron radiator is really the right answer.

    15 psig is a liitle marginal for a 3rd floor, it is possible the pressure drops and sucks air in that auto vent when the circulator is running.

    it is also possible that the loop with the baseboard is the most resistance in the system and it is more than the circulator can provide.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,605

    You should put a Pressure gauge on the bleeder on the top floor and check the pressure. You can also calculate the pressure, but a gauge is better. You need 4-5 PSI at the top with the pump off. Thats the first thing to try.

    If those two pipes show up in the basement and they only feed that one radiator and the Finn tube you could stick a circulator on it in the basement. Wire in a thermostat and a relay and a balancing valve on the second floor rad.

    Maknouf

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