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Moline System

Any thoughts on an old Moline system that was bastardized.  The ejector is gone.   The rads still have the hand and return valves from Moline.  I have 4  air vents in the basement.  Will this system ever run like it did in the old days?


  • Boiler wrestler
    Boiler wrestler Member Posts: 43

    They made a great system, and I have straightened out a some bad ones. Vapour is a beautiful thing. Please post photos of the remaining near boiler piping. I've only seen one remaining ejector in a house that's for sale, but the wife won't move just so I can have a Moline system.
  • Dave in QCA
    Dave in QCA Member Posts: 1,785
    A Moline will run great, if....

    If all the inlet and outlet valves are in place on the radiators, the system should run fine. Even if the ejector, condenser, and vacuum vent check are no longer there, it will till work pretty well.

    The important thing is that every radiator must have the original valves or if they have been replaced, you have to put in a plate orifice in the new valve. Any mixture of rads into the system that are set up with a conventional inlet valve and outlet trap will reek havoc with the system. Likewise, changing out a Moline inlet valve with a regular valve that is NOT orificed with also prevent the system from operating well. The primary orifice is the slotted cage in the inlet valve. The outlet valve also has a minor yet important orifice effect.

    The return lines must be vented. Since there is a chance of steam getting into the return line and/or water backing up if the pressure gets to high, a main type trap with both temperature and float is in order, i.e., Gorton 2 or Hoffman 75. You may need more than one vent depending on the size of the system. Generally the mains in a Moline system did not have main vents, but adding them might make the system operate even more balanced than without, which is still very good.

    Important to have the control pressure set with a vapor stat at 6 oz. When changing out a boiler, use 10-15% for piping loss but do NOT figure a pickup factor.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
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