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Fan Coil on One Pipe Steam

A second floor condo renovation in a five story building is looking to replace most of the radiators with a fan coil tied into the one pipe steam system. We can't drop a return line through the condo below. I say it's still possible to make it work, though it may be impractical. Has anyone successfully done this, and what's your secret?


  • Ted G
    Ted G Member Posts: 63
    small boilers

    What about putting small boilers in the upper floors for the fan coils?
  • Nelson_6
    Nelson_6 Member Posts: 24
    One Pipe and Fan Coils

    I have never seen that work, Joe, especially when the remainder is served by cast iron radiation. I will tell you why.

    Firstly, the fan coils tend to be low mass copper tube coils with aluminum fins, incompatible with cast iron on the same zone, same as you would not combine fin-tube and cast iron. Uneven heating and all that.

    Secondly, one pipe steam in particular works on cycles. Steam is present, then sometimes it is not. Air, as a heating medium, has almost no mass. The temperature is a volatile variable and will surely run hot then cool then hot again... Not a way to make people happy. The use of control valves is not really practical and so you are at the mercy of the steam running or not. If there are cast iron radiators, chances are, the steam may not be due to coasting between cycles.

    Now, steam fan coils operated as 2-pipe but maintaining a constant supply steam pressure, you have a shot. Steam would always be available on demand.

    Such systems tend toward commercial/institutional work and operate at a higher pressure because steam valves are required. They need some pressure to establish valve authority. Otherwise the fan coils operate at the mercy of the steam's availability.

    I would consider what Ted suggested, using a separate HW boiler and control their destiny.

    My $0.02

This discussion has been closed.