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steam venting two pipe system

So I came across a job where the two pipe steam system has some rooms that are not heating and others that are over heating. All the cast iron radiators have a valve on the inlet. There are no steam traps. But on all the condensate returns in the basement from the radiators, there are steam vents. Dole #95 should i be looking at these to balance this system.
The H.B. Smith 18 series-5 is over sized for the radiation in this house. I came up with 544.5 sq' needed, and this boiler is rated at 1188 sq' One other issue is a four season room, they installed 15' of cast iron baseboard and installed a steam trap on return side within the baseboard end cap. This baseboard gets no heat at all. Am i looking at a stuck closed steam trap here. Any insight would be appreciated

Bill

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    OK. this puppy really is two pipe -- and it sounds like it -- and there are no steam traps on the outlets to the radiators, it probably is one of a variety of vapour systems. A picture of a radiator outlet arrangement would help identify it.

    First, if it is -- what pressure is it operating at? If it really is vapour, anything over a few ounces (say 6 to 8) per square inch is too much. If it is an orifice controlled system, or has passive devices on the outlets, not only is anything over that too much pressure, it will pass steam into the returns and you will get no heat, or erratic heat. So... step one. Vapourstat, set to cutout at 8 ounces.

    Now. With that terrifically oversized boiler you are going to get considerable short cycling, even just maintaining heat -- never mind recovering from a setback. You are going to have to live with that. Sorry.

    Third, you say "on all the condensate returns...". Are these dry returns? That is, well above the water line? Or are they wet returns? In either case, they have to be vented. However, those vents are not used to balance the system (in fact, if they are on dry returns, they really can't). Balancing the system, if you find it is required after you get the pressure in line, is done with the valves on inlet to the radiators; they need to be set so that each radiator gets hot across at about the same time as any other (except if there is a space which is too hot -- then just turn it down).

    Last. For now anyway. Where does the return from that trapped baseboard go? Into a vented dry return? If so, check it after the pressure is under control -- it may just be getting back presssured from another radiator. But if it does into a wet return, there has to be a vent after the trap but high up, to allow air out.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • radiantking
    radiantking Member Posts: 7
    Great info, I'll check pressure switch, it was set low I just don't remember exactly what pressure it was at. I'll check further on the baseboard heat and steam trap. I have two pics of vents in basement well above the water line.
    Thank you
    Bill
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    The vents are probably too small -- particularly with that boiler -- but the locations are OK.

    You're going to need a vapourstat -- a pressuretrol or anything like that just isn't going to do it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fizz
    Fizz Member Posts: 547
    A possible quick fix to set thermostat at 3cph if you have this setting. It will cycle-off before pressure gets too high and serve as a controlled short cycle affect.
  • Steamhead
    Steamhead Member Posts: 15,752
    What Jamie said. You need more venting.

    Are the vents in the picture all the way out at the end of the system? Do the pipes the vents are on drop down to a common return line near the floor?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • radiantking
    radiantking Member Posts: 7
    Yes at the end of system and the pipes drop down to the common return at floor