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Should condensate lines be cool/warm on 2-pipe systems?

rhodebump Member Posts: 152

We have 2-pipe radiators. Each 2-pipe radiator has a steam trap in the tail where it has a line for condensate. I have noticed that the steel pipe condensate lines are extremely hot, like hot with steam. Is this normal?

From my understanding, steam traps should keep the steam in the rads, so the condensate line should stay cool (at least not as hot as the pipes carrying the steam).

Another possibility is that there are failed open traps in the system and it's filling up with steam so every condensate line is super-hot steam. Is this possible?

Thanks for the help.



  • ScottSecor
    ScottSecor Member Posts: 863
    It is often difficult to determine if the steam traps have failed or not. Ideally the condensate lines below the traps would be about 150 degrees or less. In the real world I've seen condensate lines showing 210 on my infrared thermometer.

    Your premise is correct though, in almost every steam system the condensate pipes are cooler that the steam supply pipes under normal conditions.
  • Jamie Hall
    Jamie Hall Member Posts: 23,428
    It's almost impossible to tell without using a good IR thermometer. The condensate will, after all, be very nearly as hot as the steam! However, in principle the pipe a few inches below the trap should be at least 5 to 10 degrees cooler than the steam inlet pipe. One does need to be careful with IR thermometers, though, and make sure that the paint or other finish you are shooting is the same in both locations, as that can make a big error.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,075
    Enough steam in the return can close good traps and those rads may not heat very well. The rad with the bad trap may heat the hottest.
    A simple FLIR gun would let you see things much better.
    $350-400 will get you one.

    Or if you have the time and patience, you could shut the inlet valves completely off one at at time. The rad with the valve off and cool on both ends may be the bad trap. If one trap is causing all the piping to be super hot and it has no steam going thru it then the pipes may cool down somewhat. This may work if you have only 1 bad trap, several bad traps would have you chasing around a lot.