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Balancing 2 pipe system

SeanBeans Member Posts: 518
Forgive me.. I have a problem that I need some help with.

the company I work for replaced a steam boiler. The old boiler was a gigantic ARCO original to the 1920's house. The whole basement is finished and the end of mains are hidden somewhere in the ceiling/walls. It's a 2 pipe trane vapor system

We replaced almost every radiator shut off valve in the system. A lot of them were the original trane valves and were stuck open.

since the install, the customers master bedroom has been much colder than the rest of the house. It seems to be the furthest from the boiler. I'm not really sure what to do. I don't work with 2 pipe systems often. I guess one far-out option would be to move the thermostat to that room but then perhaps the rest of the house would overheat. Perhaps we could do that and throttle down the rest of the radiators.

I need more opinions if anyone could help. 

More info:

when the installation was complete and we went to fill the boiler, there was an under ground wet return leak that wouldn't allow the boiler to stay filled. Another crew came behind me and jack hammered about 40' of wet return up and it was completely rotted thru the whole length. It's hard to say if they changed any steam vents at the end of the main, I'd have to dig in and find out who was there and what they did. 


  • bburd
    bburd Member Posts: 893
    edited January 2023
    The problem is most likely related to shorter heating cycle time from a new thermostat, and/or insuffiicient main venting.

    if you installed a digital thermostat, make sure it's set for steam/hot water in the installer menu, typically one cycle per hour. Also check to see if the thermostat is compatible with steam heat, some are not.

    You may have to open ceilings or walls near the ends of the mains to find the vents.

    Steam pipes are meant to be insulated. This can contribute to the problem as well. 1 inch thick fiberglass is best practice, and it's not generally available at big box stores.

  • Jamie Hall
    Jamie Hall Member Posts: 22,972
    OK. Two possible problems.

    First, Trane -- and other -- vapour systems have main vents in one place and one place only: at the boiler, where the dry returns connect together before they drop down to the boiler. So don't expect to find main vents anywhere else.

    What they do have is crossover traps at the ends of the steam mains, connecting to the matching dry returns. I do hope that first, those are still there and that they are functional, and second that some idiot didn't bury them in a wall. If they have, you are going to have to find them and check them. There will also be corresponding drips to the wet returns at those locations.

    Second,, the Trane valves were calibrated for the radiators they served. It's highly unlikely that the new valves are, or are even close. Replacing them, rather than repairing them, was a mistake, but that's over and done with. (They were stuck open, by the way, because once they were adjusted at system startup, they never need to be touched again.)

    Your first project in balancing the system is going to be to control the maximum pressure. You will need a vapourstat, and you will need to set it to cutout at no more than 8 ounces, repeat OUNCES, per square inch.

    The second project is going to be to control the steam flow to the radiators. It is possible that you may be able to use the new valves to throttle the flow adequately. On the smaller radiators, they may have to be almost closed, but it's worth a try. This is a cut and try procedure. Your goal will be to have the radiator heat up, but only to the last section The other possibility is to obtain and install orifices, sized to the radiator, in the unions between the new valves and the radiators. They will substitute for the adjustable orifices which were built into the Trane valves. This is also a cut and try procedure; there are guidelines for orifice size, but they are just guidelines.

    That master bedroom problem may be a little more pesky. If the steam main serving it has a crossover trap which is stuck closed, which is unlikely but possible, it will indeed be very slow to heat. This could also happen if the associated dry return has no drip, or worse if the drip from the steam main and the dry return join above the water line -- as might have happened if the wet return were replaced to high, or the boiler water line set too low.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • clammy
    clammy Member Posts: 3,095
    Are these wall convectors or radiators ,are they equipment w traps or water seals . Usually the main vents are at the end of the steam mains and or the dry returns before they drop into a wet return . Some trane systems I ve run into did not have cross over traps but did have Hoffmann 76 vacuume vents on both the dry return and steam mains . I would say your best bet is to pick up a few access doors and a borescope ,cut your self a few holes and take a peek .aside from possibly lack of vents or just ancient vents that have served there time , just a few other things I de chk ,is the boiler equipped w a cycle guard if so get rid of it , I ve found that on some system that a cycle guard does not permit the system to completely heat up before it cycles on the thermostat and if fact radiator at the end of the mains never fully heat ,has any one sat and observed the boiler operate and determined that it is in fact running flat out no cycling on pressure or low water if all that checks out fine if not figure out why and correct it , I de disconnect the return line from the issue rads and ensure that there’s not clog ,clogged return mean little to no heat blow it out w a air compressor . A few other things to consider ,there location in relationship to the boiler and the steam main that serves it . Are the steam main in condition space and are they insulated ,steam gets lazy and w out insulation its even lazier and forget about end of the line radiators . Last 2 pipe trouble shooting tip make sure steam is not by passing into your dry returns either from a bad crossover trap or radiator trap , high system pressure and water seal type trap and especially w convectors w no traps at all but w orifices . If steam is pressurizing the return there will be zero steam distribution it will stop dead in its tracks . Just rambling but also when disconnecting radiators to check the dry returns see it the pipes lift excessively due to settling it happens usually it will form a water leg and stop the radiator from venting correctly if heating at all . Don’t discount the water volume of the old compared to the new and also the difference in water levels ,if all the end of the mains and returns are hidden ,I would also look at if you lost a water seal out some where in the system w the new water line
    Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • mattmia2
    mattmia2 Member Posts: 9,475
    SeanBeans said:

    We replaced almost every radiator shut off valve in the system. A lot of them were the original trane valves

  • mattmia2
    mattmia2 Member Posts: 9,475
    edited January 2023
    Also, that arco had a very high water line (probably a 40's replacement, not the original form the 20's, but still an old style boiler that was more forgiving of a lot of things).

    The probability that a drip that was below the water line is now above it is great.
  • JSoler
    JSoler Member Posts: 2
    edited January 2023
    How many valves are in the system. If not too many, I'd locate overheated areas and throttle valves down significantly and see how your end of line line radiatos are affected. Document adjustments and results. This may be a simple flow problem. Do shut off valves have internal limits or balancing adjustments like those used on Dunham Bush Vari-Vac Systems? I'm a Steam Operator, Troubleshooter, for over 30 years. Hope I could be of help, Jim...
  • Steamhead
    Steamhead Member Posts: 16,736
    There were several variations of Trane Vapor. Some used crossover or F&T traps at the ends of the steam mains and a single vent near the boiler as @Jamie Hall said, others did use main vents. You'll have to open the walls at the ends of the steam mains to see what's there.

    Post some pics when you do, and we'll take it from there.

    Also, where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service