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General steam trap question

As the facilities director for a group of museums, I do more HVAC stuff in house every year. I do know, however, when to pick up the phone. Recently we (my retired engineer volunteer and myself) found a steam coil in a new air handler ice cold. To make a long story short, a ca. 1958 F&T trap had a split-in-half float valve and a disintegrated thermostatic valve. (Funny how expensive PM contracts in the past never addressed these.) At any rate, a replacement cover took care of that and the coil is fine. We saw another one near by, ordered another cover and it too needed it. Now, there are maybe 30 or so in-the-wall radiators with vertical thermostatic traps. We took the easiest one to access (large metal cover) and removed the trap. Sure enough, the bellows was full of cracks. We obtained new guts and all is fine. There are maybe 5 more with big metal covers that will be equally easy. But the rest seem un-reachable! There is just a metal grate in the drywall about three feet up for the exiting hot air. And down below in the wooden baseboard is a decorative cut out for the entering air. Down on my belly, I can see the trap but removing it seems impossible. I can assume that they are all ca. 1958 and in the same condition as the one we rebuilt. How am I getting in there with wrenches? Is this a common problem? Do we live with the inefficiency of failed traps (these radiators do get hot) or embark on some drywall/carpentry adventure?


  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    trap removal

    what about using socket wrenches with extension pieces?--NBC
  • Jamie HallJamie Hall Member Posts: 6,693
    First step

    is going to be finding out if the traps have failed.  They can fail in two ways: either stuck open or stuck closed.  If they are stuck closed, it is likely that the coil won't heat, or will heat very poorly (relatively speaking, that is).  If they are stuck open, the problem is that steam can get by them on longer heating runs, and build pressure in the returns -- which will cause other units on those returns to not heat properly.

    If they are stuck closed, the only real recourse is to repair them.  As NBC suggested, is there any hope of reaching them with an extension on a socket wrench?  Bit cumbersome, but might work.

    On the other hand, if they are stuck open, it might be possible to cheat.  Cheating, in this instance, means going back even earlier: if there are inlet valves on those units where they are failed open, and those valves are capable of throttling, and your pressure is low enough (that is important!) you can partially close those valves to simulate having an orifice on the inlet, restricting the steam flow to just that which can be condenses in the unit, leaving none to escape.  Might be worth a try...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Dennis KunkleDennis Kunkle Member Posts: 34
    Can you explain...

    .....what you mean by building pressure. The return lines all go to a condensate tank in the boiler room that is vented. Does that change anything? All of these wall radiators get hot. So we don't have completely blocked traps. I'm assuming that the traps are suspect because they are all ca. 1958 and the one that we checked had a bellows riddled with cracks. I thought that if steam was getting by the trap, it was an efficiency ($) issue.Please correct me at will. As far as the tools for removing the vertical thermostatic traps under the radiators, it takes 2 open end wrenches to loosen the coupling above and the same underneath.And one needs a certain amount of space to position and turn them and it's not there....LOL.
  • JUGHNEJUGHNE Member Posts: 3,247
    edited March 2014

    Your description sounds like a project I had ( still have). When you say vertical traps I assume they resemble the "look" of a wye shaped vertical check valve. Are you able to remove the side cap to gain access to trap element only??  I have a 1955 schoolhouse with Hoffman angle traps that were buried behind bookshelves,  obviously original as I had to cut thru 1955 bookshelves to gain access.  After such APITA all elements were going to get changed.  I did discover that the inlet valves had orifices installed (over-sized or washed out too large) but still new trap elements were installed and smaller orifices put in the valves where possible.  Most change-outs needed a one hand operation of an impact driver. (extensions as needed).  You may not have the liberty to cut things open as this.   

    If you can only access the inlet valves, maybe the theory of Henry Gifford's  "How to make a 2-pipe steam heating system really work" will help.  I used that in addition to new steam traps (elements only).  Also the impact driver/socket gets a back-up wrench on the trap body or lower pipe because SCH.

    BTW the 1955 schoolhouse valves even when shut tight with the smaller orifices installed would still heat (but not overheat too bad) with only 2 Lbs of pressure on the system.
  • Dennis KunkleDennis Kunkle Member Posts: 34
    The type has... inlet and an outlet; nothing on the side. For the one that we did, we used a Barnes & Jones 3146 kit. It must be completely removed so that the original seal on the bottom can be removed. The kit is then inserted and the trap is screwed back together. It's then hand tightened on to both unions. Then 2 wrenches are used to tighten the unions. And, of course, there's minimal amount of space needed to perform this and the fact that this trap is in a tight space behind the baseboard, I'm lost.
  • RobGRobG Member Posts: 1,850

    You should post this question in the "Strictly Steam" section, you will get a lot more help there.


  • Dennis KunkleDennis Kunkle Member Posts: 34
    No moderators, huh?......

    .......well, at this point, I think that I know the answer. If I can't get at them with tools, I either live with highly probably suspect 56 year old traps or cut away some baseboard and patch in carpeting.
  • gennadygennady Member Posts: 680
    bad apple

    The bad trap, failed in open position will turn off nearby traps and cause them to fail. It is like a bad apple.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • ChicagoCooperatorChicagoCooperator Member Posts: 195
    Sounds like Trane Concealed Heaters

    It sounds like you have Trane concealed heaters or similar - do a search on the site for them and there is a rough diagram in one of the Trane brochures about how to remove the convector for servicing (you have to drop it down somehow). There is another company which made similar ones and I think they have instructions too. Their brochure is also on the site.

    Good Luck!
  • JohnNYJohnNY Member Posts: 1,822
    Thermal imaging and trap testing

    We use a thermal imaging camera to test traps. It eliminates a lot of guesswork.

    That's a good thing.
    For private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • Dennis KunkleDennis Kunkle Member Posts: 34
    I watched some Youtube videos about that.......

    .......and the fellow that works for an engineering firm that does some pro-bono stuff for us from time to time says that they use a high end hand held temperature sensing gun. The thing is, these thermostatic radiator traps are 56 years old! I want to rebuild all of them. This 1920s building was a car dealership at that time. In 1958, it was bequeathed to us and had a major renovation. A few radiators, maybe 5, have big metal covers that make servicing them a breeze. The rest are built into the walls with just an opening in the baseboard. If the opening was a little wider, trap removal would still be an on-your-belly struggle with pipes stuck on the wrenches for more leverage, but doable.
  • Mad DogMad Dog Member Posts: 3,180
    Yes.....large sockets, breaker bars and......

    every other specialty wrench you own.  Also, prepare for bleeding knuckles.  NOTHING is impossible.  Good luck.  Mad Dog
    To learn more about this professional, click here to visit their ad in Find A Contractor.
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