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Hartford loop sizing

The back pressure from the boiler side is obviously the same on both sides; I wonder why the pressure in each main isn't the same. Is it happening early in the cycle, before the vents close, or all of the time, or something else altogether?



  • James Crosby
    James Crosby Member Posts: 3

    Crown JBF-92 9 section boiler, all near boiler piping is to factory spec and rises to a 3" main 80'long on the left and a 2" main 80" long on the right side. Where it goes astray is that the water stack's up on the 2" return side and spits water out the main vents, even though all the near boiler piping has been replaced and the system is well designed and balanced.

    For the life of me I just cant wrap my head around whats going on here, as the water would seek it's own level in the Hartford loop and equalize with no problems, What is it that I am missing?
  • got pictures?

    How are the two returns connected to each other? Do they both drop to the floor before tying together?

  • James Crosby
    James Crosby Member Posts: 3

    Both returns are 2" and drop 6' forming a prefect horse shoe loop connecting in the center with a 2" cross tee, total width is 6' wide, there is a 2' flush valve installed in the middle of the loop and both sides are completely clean.
  • James Crosby
    James Crosby Member Posts: 3

    It happens in the middle of the cycle on cool fall or spring days almost like it's an insulation problem on the 2" side, however the insulation is all brand new stuff and of high quality.

    Do ya know what I'm thinking, is some how in the 2" main there is a return problem with one of the risers dropping in wrong and cooling the steam at that point and causing a back up, is that a plausible theory or am I way off base? cuz it seems the Hartford. loop would equalize any return rate diffrences
  • In my mind's eye

    I see the boiler (and Hartford Loop)pressure being equal to both, so not part of the problem. It lifts both sides equally.

    I see the issue as a difference in pressure between the two returns.

    The short return will be either almost AT boiler pressure (this is a one pipe system, isn't it?), or the main vent is still open.

    The long side is going to pass more air, so it's vent would need to be large enough to handle it without pressurizing that long main. If the long main saw pressure while the short main was still venting, and the pressure were a couple PSI, I could see this happening till both vents were closed. Not too likely, though. The short main should get hot first


  • James Crosby_2
    James Crosby_2 Member Posts: 6
    Bizzare but plausable

    Both mains are 80' each for a total of 160' run around the house. both mains are vented at 65' foot at the last riser, 3" main has 4 maid o mist #1 vents and the 2" main has 3 #1 maid o mist main vents. (Ya I know the vents are shady, but there all new and on all the rads for the moment till money allows the total replacement with the good stuff later this year)

    I think you may be right on with the pressure difference and will adjust venting to allow a more balanced system, Thank you for your thoughts on the subject Noel and have a good day.

  • Al Corelli_2
    Al Corelli_2 Member Posts: 395
    Al Corelli, NY

This discussion has been closed.