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Boiler Piping questions

I have been looking at Installation piping for my Dunkirk PSB-7D. I have a one story home two pipe gravity vapor system. I am going to try to have a plumber use both supply tappings to get drier steam and a proper header etc. I have a couple questions with my boiler piping.

1. I have one steam main that travels about 35' down the center to the front of the house then has a T that creates two loops for each side of the house. The "Steam Main T" photo shows this as best as I can draw it. This is also why I have two steam main returns as seen in the "Main Returns" photo. Is this wrong? I am not sure if there should be two lines that run the length of the home to create both loops. This would have been the original way it was piped as there is no evidence of a second main being piped through basement walls.

2. If I utilize the second Boiler tapping I would need to extend the header enough to keep a 15" minimum from the second boiler tapping and the steam main on my header. Would i be able to re route the equalizer so it can connect to the hartford loop that is in place? Didn't know if this needed to be a straight drop from the reducing ELL to the Hartford Loop.

3. Since there are no main vents on this system do I understand it correctly that I would need a main vent on each of the steam main returns (15 inch minimum from the drop to the wet return) as well as the condensate return that is connected together with a T before it drops to the wet return? Would I get by with a single main vent on the condensate side right above the T or would I need two main vents 15 inches from where they connect to drop to the wet return.

4. Why would I have that 15 gallon tank connected from the water feeder to the boiler?

Thanks again for all the help. This website has given me a lot more knowledge on how to revive this steam system.




  • Here is the correct picture

    for the Main T Drawing
  • VA_Bear
    VA_Bear Member Posts: 50
    A thought...

    #4 first - Do you know anything about the previous boiler in this building? Is the tank piped into the wet return for the boiler? I'm wondering if the previous boiler was a high volume design and was replaced with a boiler which doesn't hold anywhere near as much water. if that was the case and the boiler ran low on water until the condensate started coming back and the tank allows an extra water to keep the water line from shutting off the boiler at the low water cutoff.

    1-3 - Are you having a problem with the system which prompted your look into the configuration or is this learning expedition?
  • old boiler

    I am not sure on the old boiler. We purchased the home 8 years after the original boiler was removed. I may be able to find the installer and he may have that information on file or may just remember.

    We stopped using the steam heat after we had heating bills of over $700 (2500 sq/ft home) the first winter we moved in. We had also upgraded the central air (one story home with the central air running in the attic) the first summer we were in the home and decided to get a heat pump with some electric emergency heat. Even though we haven't used the steam in a few years it still works and I recently had it on when our heat pump broke down and it was great heat (for the rooms where it worked). So I have been reading to try to understand how I can make steam more affordable and even. Through reading a lot of the books on this website, I have found that there were a number of things wrong. First I was running at the highest pressure the pressuretrol would allow on a vapor system. I also didn't have any main vents, in fact the only two vents were one pipe radiator vents that were added to the two pipe radiators. There was also zero insulation on the pipes. Just yesterday, after I posted on this wall about my KELMAC traps, I opened them up and have found out that all my traps are empty of any thermostatic elements. So I believe my system just threw steam where the two radiator vents would allow the air to make room for steam. I forgot to mention that even with high heating bills, many of our rooms were cold making the move to the heat pump easy at the time.

    So, long story short, my main piping may work just fine with a vaporstat set to the correct pressure, a few main vents on the ends of the steam and condensate lines, insulation, and getting my traps fixed while getting rid of the couple radiator vents. This may be the first steps to getting the system balanced and working well but I haven't seen any diagrams that showed how my steam main branches out to two loops and thought this may be an issue that may cause problems that traps, insulation, etc. cannot fix.


  • VA_Bear
    VA_Bear Member Posts: 50

    your boiler room was toasty warm with that uninsulated tank! I highly suggest you get a copy of The Lost Art of Steam Heat and read, read, read. I would start with an insulation inspection of the piping system. With the utility bills you mention, it sounds like the insulation is gone from the piping and you have a giant radiator under the house and, yes you will use that much energy to keep the pipes hot (I have measured 30 to 80% loss in un- and under-insulated lines.
  • Jamie Hall
    Jamie Hall Member Posts: 21,546
    That branching

    to two loops really shouldn't cause a problem; it's common enough that mains go somewhere and then branch.

    Nor should the main returns -- although it is a little odd.  On the other hand, it makes it simple to add the main vents, they can go right there at the boiler, which is ideal.

    As to that tank... it might be there to compensate for slow returns.  It might also be... who knows?!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jason_13
    Jason_13 Member Posts: 304

    The one quick thing I see wrong with your proposed drawing is that your one Tee for system riser will be between two boiler risers. You never want a system riser between your boiler risers all your system riser should be after the boiler risers. Of course the second is no pipe insulation.