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Radiator stone cold

  1. Oct 24, 2016 #1
    Turned the boiler for the first time this fall and an upstairs bathroom rad is stone cold. All other rads heat up. I fiddled with the valve, which is new, with no luck. What is strange is that even the pipe from the floor leading to the valve is cold. This is a water system. It must cycle. How can that part be cold? All rads were bled in spring. What are some simple things I can check or do before I call the pros?
     
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  3. Oct 24, 2016 #2

    phinds

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    The last time I had the same problem with the last radiator in the line, the problem was not with the steam valve but with the air vent at the other end. It was clogged and since it wasn't letting any air through, the steam wasn't even coming up into the pipe at that radiator.

    Try removing the air vent and seeing what happens (put a pan under it in case).

    Radiators, as I assume you know, are not a closed loop, they are just pipes with steam running up and the condensed water running back down the same pipe, not "circulating" as we normally think of that term.
     
  4. Oct 24, 2016 #3
    I'm pretty sure my setup is a closed water system, not steam.
     
  5. Oct 24, 2016 #4

    phinds

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    Oh, sorry. I was assuming steam. I don't even associate "radiators" with water, but I guess that's just my ignorance.

    In that case I don't see how it is possible. Are you SURE it's just water and a closed loop? Your problem sounds exactly like what I experienced with my steam radiator system.
     
  6. Oct 24, 2016 #5
    yeah definitely water, I had a valve leak over the summer.
     
  7. Oct 24, 2016 #6

    JBA

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    Is the new valve a thermostatic one that controls the radiator/room temperature? If so, if that valve is not opening then it is like your kitchen faucet, no flow, or circulation in your case, means no hot water even in the inlet pipe coming up from the floor.
     
  8. Oct 25, 2016 #7

    Tom.G

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    Valve re-assembled incorrectly or, if it is more than just a simple valve, installed backwards?
    (edit) Take it off and check that you can either see thru it or blow air thru it.
     
  9. Oct 25, 2016 #8

    DrClaude

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    Have you purged all your radiators? Have you checked that the water pressure in the system is correct?
     
  10. Oct 25, 2016 #9

    sophiecentaur

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    Try bleeding radiator first.
    Does the pump run normally? Pumps are quiet so you may need to put your ear close.
    Old radiators can clog up at the bottom with iron oxides.
    PS I never heard of steam heating in domestic systems. Unless the whole system is at 100+C the water would condense. Also 100C is a huge accident risk in the home.
     
  11. Oct 25, 2016 #10

    sophiecentaur

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    Supply pipe will be cold because there's never any hot water through it. Kirchhoff 1 rules.
     
  12. Oct 25, 2016 #11
    basic open close valve

    This past spring the system was drained and rads bled.

    So this is a pump or boiler issue?
     
  13. Oct 25, 2016 #12
    If the other radiators get hot, then it would seem that this radiator is in parallel (using electrical circuit terms), or somehow by-passed. So if the valve is truly open, I'd want to check the pipes leading to and from the cold radiator. Is there another valve there, is there a clog in that part of the loop?

    Was the system tested after the valve was replaced? Maybe another valve was shut off to facilitate the repair, and was forgotten about?

    I'm assuming the pump is OK if you are getting good circulation to the other radiators, but I suppose those might be able to get hot from convection? Maybe, but unlikely?
     
  14. Oct 25, 2016 #13

    phinds

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    Huh? I'm in central NY and pretty much every house here older than a few decades is heated by steam. My understanding is that that is common across the Northeast.

    EDIT: I might need to make that several decades, not just a few.
     
  15. Oct 25, 2016 #14

    sophiecentaur

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    Well well. You live and learn. It obviously (I now appreciate) has advantages in big instalations (High power transfer) but the hazard of hot pipes and the problem of two states in one circuit would imply that specialists would be needed to design and instal systems. Not common in single dwellings, apparently.
     
  16. Oct 25, 2016 #15

    sophiecentaur

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    Is that rad the highest in the system? You may have lost water down to that level. Header tank could be empty or pressure vessel low. Minor leaks don't always show as dribbles can evaporate with heat.
    Remote fault finding is difficult, even for PF.
     
  17. Oct 25, 2016 #16
    2bd floor but no higher than the others nearby. Boiler apparently has an auto fill feature.
     
  18. Oct 25, 2016 #17

    sophiecentaur

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    Go for easiest first. Bleed rad then take next step. Is the boiler only for your home?
     
  19. Oct 25, 2016 #18

    phinds

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    No, I am TALKING about single dwellings. Steam heat was very widespread in new houses for many decades in the Northeast and hundreds of thousands (probably more) of these older houses are still around.

    The hot pipes are trivially easy to insulate and the radiators have covers to prevent kids touching them but you are right about it being an issue that there is both steam and water in the same pipes. This is the cause of the notoriously obnoxious "banging" that you can get in steam systems. It happens in live steam systems because the condensed water rolling back down hits live steam going up and this causes the water to suddenly become steam again and thus there is a rapid expansion in the gas volume and this causes banging in the pipes.
     
  20. Oct 25, 2016 #19
    Maybe the water is preferentially going through the radiators which are working because that path offers much less resistance to the flow.
    You could try closing valves on the working rads and see if that results in the hot water now going through the one which wasn't working,
    (As that is now the only path available).
    If you get some success with that, then you can try setting those valves to some intermediate setting.
     
  21. Oct 25, 2016 #20

    russ_watters

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    Can you post a picture of it?

    Even if you bled it in the spring, it is still a good possibility that it is airbound now (edit: especially if you had a leak).
     
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