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Single zone steam: uneven heating in a 4 floor house

My in laws live in a 4 floor brownstone that has a strange issue. It has radiator heating driven by a steam boiler.

Here’s the problem: the thermostat controlling the radiator for the entire house is on the 3rd floor, so I understand it’s a single zone system.

If I set the 3rd floor radiator to 70:
- The 4th floor will get to 80 (I then have to turn on the AC in winter, which seems like a horrid waste)
- The 3rd floor will get to 70
- The 2nd floor will get to 65

If I set the 3rd floor radiator to 75:
- The 4th floor will get to 85-90 (AC goes on)
- The 3rd floor will get to 75 (AC goes on)
- The 2nd floor will get to 70

Has anyone seen a phenomenon like this? Any idea of how to handle it?


  • KC_Jones
    KC_Jones Member Posts: 5,738
    I’m assuming this is a single pipe steam system.

    You have a classic venting/balance issue.  The fix starts in the basement.  First need to know what they have for main venting, if none then it needs to be added.  If it is there need to know how long and what pipe size the mains are to determine it it’s enough.

    After that need to look at the vents on the radiators.  They should be set up (to start) with slower vents on the lower floors and faster vents on the upper, but also factoring in radiator size, more venting on bigger radiators, less on smaller.  The final piece is then the temperature desired.  If rooms are getting too hot you slow those radiators down, if too cool you might speed those up.  For all this remember, small changes can make big differences so be patient and allow each change to got for a day or two before making the next change.

    It would also be good to post pictures of the boiler piping just to make sure it is correct and they can realistically expect to get proper performance from the system.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • bburd
    bburd Member Posts: 918
    It’s unusual for the top floor to be so hot unless insulation was added after the house was built. In that case, you may need a smaller radiator, or to slow the venting way down, or even to install a thermostatically controlled vent valve on that radiator.

    As noted above, this is a question of balancing which should be doable.