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Minneapolis Steam Control System

TMH Member Posts: 1
My old house (3700 SF) is heated by a one-pipe steam system powered b y a relatively new Smith GSX residential boiler.
Heating is very uneven. Radiators nearer the boiler heat quickly and satisfy the thermostat while those farther away heat slowly and incompletely. I recently discovered what purports to be a solution to this problem known as the Minneapolis Steam Control System in a paper written by one George Peterson. This scheme involves the installation of a relay in parallel with the thermostat wiring. When the thermostat is satisfied the contacts in the relay close and the boiler continues to fire until shut down when the far radiator vents close and steam pressure reaches the pressurtrol cut-off setting. A description with wiring instructions can be found by googling: "Correcting Uneven Heating in Single Pipe Steam Buildings: the Minneapolis Steam Control System George Peterson Minneapolis Energy Office". Is this a
viable solution to my problem?


  • mattmia2
    mattmia2 Member Posts: 9,747
    edited March 2020
    It would probably be better to make sure your main venting is functional and adequate then put faster vents on the radiators that heat more slowly and slower vents on the radiators that heat more quickly.

    If you just hold the cycle longer you won't solve the balance problem, you will still overheat some rooms while just heating other rooms just enough. It is approximately equivalent to just turning the thermostat up.
  • Fred
    Fred Member Posts: 8,542
    You just need to balance your system. Large capacity vents on each main, after the last radiator run-out, either one or more Gorton #2's or a Barnes and Jones Big Mouth, depending on the length and diameter of each main. Once that is done, adjust the capacity of each radiator to get the steam/heat where you want it. You can install adjustable radiator vents like the Vent-rite #1 or Maid-O-Mist that has multiple orifices. That way you can buy the same vent for all the radiators and make the adjustments as needed without trying to buy different size vents.
  • Steamhead
    Steamhead Member Posts: 16,894
    @TMH , where are you located? Can you post a link to that paper?

    I agree with @Fred and @mattmia2 , you need to upgrade your main vents.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
  • mattmia2
    mattmia2 Member Posts: 9,747
    "In addition, large main line air vents were added which cut the maximum difference in steam arrival time
    in half"
  • emfriction
    emfriction Member Posts: 3
    these guys are correct, sounds like a venting issue. however, does this happen to be an older home? if so you may want to check the one pipe system main that runs out to the further away radiators which are not heating as the main may have lost a hanger and is drooping creating a water trap.
  • BobC
    BobC Member Posts: 5,479
    I agree that the steam mains should be checked to be sure they are pitched correctly and there are no bellies in the pipe that allow standing water - those kill steam.

    Correct venting is also a must. How many steam mains and what is the approximate length and diameter of each main? What vent is on each main?

    What kind of vent is on each radiator? The vents should get larger as the radiator size and length of pipe from the steam main to that radiator increase.

    In most cases the mains sb vented very fast and that radiators slowly. The main vent sb much larger than the sum of all radiator vents on that main.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge