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Planning to add 2 radiators to a one pipe system directly above the boiler

Hi pros,

Currently, my one pipe steam boiler is oversized for the radiation in the house.

I'm planning to add 2 more radiators that I got for free to the system to help with this. The total output of the radiators will be about 2,304 + 3,072 BTU or about 22.4 EDR.

These radiators will go into two rooms pretty much directly above the boiler, one on the first floor and one on second floor. Why these rooms have no radiators, I have no idea.

I did read Dan's book and I do see he typically recommends a drip to a wet return for this.
However, the radiators are going to be directly above the boiler in my situation. The riser run-out could technically be the riser as well and run vertically up from the main. Is this allowed or should it be done another way to implement the drip to a wet return?

Thanks in advance


  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    The radiator risers can go directly into the main -- provided that the condensate then has someplace to go other than trying to get back down the main boiler riser or risers. This would be the case if the main were parallel flow, or if the main is counterflow the connections are downstream (from the standpoint of the steam) from the drip from the counterflow main. In any case, the radiator riser must take off downstream (from the steam point of view) from the connection from the header to the main -- never go straight up from the header to a radiator riser and take the main off the leg of a T.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,818
    edited October 2022
    I almost understand what @Jamie Hall said
    I think this is what he is saying.

    Don't let the condensate drip someplace where the water can flash into steam when it hits a steaming pipe. it needs to flow sown the sides of the vertical pipe and then down 45° pipe so it returns to the condensate flow without dripping on something hot enough to make it flash into steam again. Best Practice is to have the Green (A) piping arrangement Stay away from the other two. That may end up with a very noisy result
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • br0ok1ynb0i
    br0ok1ynb0i Member Posts: 2
    Makes sense, thank you both. I also plan to add the slowest vents to both of these radiators to keep venting as slow as possible. And probably will use the next pipe size up for the rad riser to 1 1/4" to prevent any issues with condensation flow.

    I will probably look into doing this in the next summer and hopefully remember to post the results. :smile: