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Replacing an ancient vacuum/vapor/sort of 'Moline' two pipe system

zippy Member Posts: 19
Apologies to those who offered suggestions last year about this time when I wwas starting the redesign of my old 2 pipe vapor/vacuum/sort of 'Moline' design system. The economy put a big dent in last years plans. This year for sure.

When we last left our 'hero', a 1951 McLein Weil 150,000btuh boiler, we discussed the merits of keeping this steam vs changed to hot water, and discussed what everyone thought were the most efficient steam boilers that seemed to be in the 80% range. Previous recommendations included a Burnham V9 and Smith 19A- but that has been over the passt couple of years.

On the boiler side, is there anything new out there for residential steam that may be more efficient?

Since there are lots of new windows and insulation, downsizing is a thought. Thinking about replacing old rads with Cast Iron baseboard Rads (This always seems to draw alot of comments)

Sketch of system attached

Any advice most appreciated.


  • Ideas

    Boiler: Slantfin Intrepid boiler with X4M Modulating Gas power burner by Power Flame.  No need to replace radiation to downsize.  Molines have orificed supply valves that can be rebalanced to reduce radiation and blance the system.  If some of these valves are missing, replacement adjustable orifice valves are available.

    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • zippy
    zippy Member Posts: 19

    sadly no orifices at the rads.

    Bedroom at the top of the first riser on the vacuum side is traditionally a sauna. My wife blames it on the kids moving out as soon as they finished college. Each one slept in that room before they moved out.

    I looked at a retrofit orifice from a engineering/manufacturing firm in New york that was supposed to work miracles for overheating portions of steam systems. Since we didn't use the room recently much, shutting off the rad was the most cost effective approach.
  • zippy
    zippy Member Posts: 19
    attachment didnt work the first time

  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    vacuum system

    if it were mine, i would keep the steam. i would get the pressure down to a few ounces. i would tweak the venting so that the air is no longer squeezed out of one smallish vent.

    i would find the orifice setup most suited to the system--probably metering valves, so the radiators could be regulated for each room. right now the "sauna" gets heat way ahead of other areas, probably from insufficient venting.

    at the risk of causing controversy, i will say that if the general work was done, you may get a few more years out of the old boiler, if finances are tight. whether old or new boiler you will still need the low pressure and the venting, and orifices.--nbc
  • zippy
    zippy Member Posts: 19
    vacuum system


    The payback on a new, say 84.5% boiler (The unit Boilerpro suggested in an earlier post) is really pretty reasonable given the McLean-Weil is at 65% tops. And, this year (in between the last kid leaving college-no tuition this year- my wife retiring - junior high teacher reaching PTSS after almost 30 years of the Darlings) I have an opportunity to invest in the new 'tea kettle' in the basememt. Also, we intend to stay here for a few more years given the state of the home resale economy.

    That being said, your advice on optimizing the performance is exactly what I was looking for. I started reverse engineering the system to see what it was designed to do and what the 'fireman plumbers' took out over the years. The system is 102-3 years old.

    I have started researching retrofit orifices since I noticed that those are missing early on. I am trying to be careful, because I have the oddball situation with the front of the house with one system and the back with another served by one boiler. It has scared off several local guys in my area. I also have several rads with traps, and none on most. I am told that that is the function of the 'big honking pipe'. in the diagram

    When you discuss metering valves I am not sure what you are referring to. Do you have a f'rinstance?

    Thanks for the help
  • zippy
    zippy Member Posts: 19
    one other thing

    On the venting.

    Some have recommended against adding vents on the rads. None have them. SInce I found evidence of a house vent removed, I added a Hoffman 75 the normal 15" from and 10" above the end of the main which made a great improvement in the general performance and dropped the gas cost alot.

    Doubling or tripling up the fitting to speed up the venting is a half hour pipe fix. is that what you are talking about in increasing the venting?
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    Adjustable orifice valves.

    Barnes and Jones makes 1/2" and 3/4" adjustable orifice radiator valves. "A.O." series of valves. Go figure. Access to the adjustment screw is through the valve stem with the handle removed.

    What I've done is to effectively downsize the existing radiation to the newly reduced heat loss of the home. Seek out Boilerpro's excellent article on this subject. You adjust the valves so that you limit the steam such that you only heat, say, 60% of each radiator. Size the boiler not to the EDR that YOU can see, but to what the BOILER will see through the orifice valves. Finish off by fine tuning the orifice valve adjustments so you have even heating without boiler short cycling.

    You will be shocked at how much your fuel consumption will drop. I did this to an orifice vapor system with its original valves intact. Another contractor had downsized a new boiler to save energy, but of course the boiler ran all the time with horribly uneven heating. After installing a vaporstat and setting pressure to 4 oz, All the stops on the radiator valves were reset to achieve the above criteria. The heat is even, the boiler doesn't short cycle, but cycles normally on a call for heat, with pressure cycling only on very long runs, and the fuel consumption is literally half or better of what it once was.


    PS notice that Dan has a new book coming on "greening of steam heat" which I assume is going cover this strategy.
  • zippy
    zippy Member Posts: 19
    valves and greening

    Thanks for the advice. I will check out the valves

    And I already have order the Dan H's "greening" book. His books are life savers with these old systems. Got mine under control and helpd a nunmber of freinds with theirs.
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