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Properly size F&T trap and return line.

I have looked through the "lost art of steam heating" book and have figured out exactly what I have to do. I'm having trouble sizing the return and F&T trap. We have 8 radiators draining into one return. Would 3/4" F&T work ? If so would I also use 3/4" pipe ? What about venting ? It seems to me I couldn't have too much venting but I could have not enough. Should I just get the largest vent they carry ? Maybe leave tee's with plugs in case I need more ? Thoughts on installing a dirt pocket in the wet return ?

Comments

  • Chapstick
    Chapstick Member Posts: 64
    I'm sorry, this is a two pipe system with traps.
  • JStar
    JStar Member Posts: 2,752
    What's the original problem?
  • Chapstick
    Chapstick Member Posts: 64
    Radiators not getting hot, short cycling, and outrageous heating bills. All of the radiator steam traps and valves were shot. Those have been replaced already. Return piping was retro fitted with no vent or F&T traps at some point. Return into loop is wrong and near boiler piping is wrong. I have a threader coming that's good up to 4" and it's 275 a day. I'd prefer not to have trial and error. I have the manual from Weil Mclain so I'm good with near boiler piping. I understand the principles of the return piping but I'm not sure of the sizing. 3/4" F&T trap is $180 so I'd like to not buy the wrong one. Thanks for replying.
  • Chapstick
    Chapstick Member Posts: 64
    Bump.
  • JStar
    JStar Member Posts: 2,752
    The return doesn't need a trap, but does need vents. Do you have any pictures of the piping?
  • Chapstick
    Chapstick Member Posts: 64
    I finally got home and checked everything out yesterday. I repiped the boiler exactly to manufacturer specs and it looks great. As far as the return piping, I patiently flagged every pipe with tape. Blue on the steam mains and green on the returns. With that I drew up a diagram of what I had.

    Steam leaves boiler, goes to two mains heading in opposite directions. Return main starts on furthest radiator and comes back, splits into two, one leg picks up one half the house, and the other picks up the other half. At that point I have the ends of the steam mains sitting 8" apart from the ends of the return mains. They are both running parallel and pitched in the same direction. At the very end of the runs, they tied the steam and return mains together with some kind of steam valve right before they dropped down a foot, and then piped together again, and finally dropped into a wet return. The steam was going right up the returns like a continuation of the steam mains.

    So what we have now, is those original steam valves were removed, and the mains have been unconnected from each other. Where they were connected with the original valves I now have Gordon valves in both the steam and return mains for venting and the mains dive down into a wet return which should prevent the steam from getting into the returns now. Last night approaching the finish line we realized the guy at the supply house messed up and gave us two wrong fittings. Being as it was 2am we couldn't get the right fittings so I haven't gotten the chance to test this sucker but I am confident that it will work. I may drop the wet return a foot because it's only an inch and a half below the boiler water line. IMO, a little too close.

    You guys are the best. I had no idea how any of this stuff worked only a couple weeks ago and after some reading and conversing I have a pretty good understanding now. Cheers.