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Hot Returns = Bad Traps?

DNW Member Posts: 20
I think I know what's going on, but I'm looking for confirmation:  2-pipe Trane Vapor System, with in-wall convectors.  Most of the condensate return lines remain ~ 75°F when the system is operating, but a few get up to 190 - 200.  I assume this means the traps feeding those hot lines are failed open?




  • nz
    nz Member Posts: 125


    That has been my experience. Either the trap is clogged with crud, or the thermostatic disc has failed. If you don't have a trap disc handy, I would suggest cleaning it first - or at least opening it up with the system off to see if it is clogged. Ultimately it should be replaced.

    See pic below of one of my traps, it was servicing an in-wall convector too. I cleaned the trap body, and put a new cap & disc on, and now it works well - return line directly below the radiator is now around 150-160 degrees F, which is about right.

  • Rod
    Rod Posts: 2,067
    Finding Bad Traps

    Hi Darrel -  I've been using an IR thermometer to check trap operation. I have a Ryobi 4 volt Tek 4 Model # RP4030. You can get them at Home Depot.  On a working trap you will see a 15- 20 degree difference between the inlet side and the outlet side of the trap. If there is steam present and the temperature differential is close, the trap isn't working and steam is passing right through it.  Take the readings up close as the farther you are away from the pipe, the wide the sampling area.

    - Rod
  • gerry gill
    gerry gill Member Posts: 3,078

    that would imply steam is getting past those traps..it will only get worse.. rebuild those traps soon..you should always be able to keep your hand on the return pipes at a resonable distance (few feet) from the trap..
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • DNW
    DNW Member Posts: 20
    IR Thermometer

    Rod - I bought the same one at HD.  It's been really useful in seeing when my two loops get hot when they return to the boiler, and it looks like it'll help find the leaky traps.  My convectors have the decoratve covers, and I hope I'll be able to "shoot" through the openings and read the pipe temp just below the trap.  Now that I've ID'd a couple that I know are bad by finding their return pipes in the basement, I should be able to figure out what normal and bad readings should be at the trap itself. 
  • DNW
    DNW Member Posts: 20
    Rebuild the traps

    I may wait 'til after the season to try to rebuild the bad traps.  I plan to try to ID all the bad ones this winter.  Because the traps are behind the decorative convector covers, it's pretty involved to open them up (I haven't actually tried yet). 

    One "problem" I'm having this winter is that it's been so warm, I may only get a couple of firing cycles per day to check things out!  Most of the convector return lines are in the crawlspace from H3LL, so it's impossible to get under there and actually feel the returns while the boiler's firing. I've got to find a reliable method to do it from upstairs.

    I've got a section of main with some rusted-out spots that a plumber put "repair" clamps on a couple of years ago to tackle, too.  I haven't found a plumber yet who wants to get his hands dirty, so I may take this on myself, too! 

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