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Old steam Weil McLain boiler

ishmael1980 Member Posts: 13
I am getting my house ready to rent my house. There is a 25+ year old steam Weil McLain boiler labeled with a boiler size: AB-466E-HE. It was originally oil fired but converted to natural gas about 8 years ago. It's a single zone one-pipe steam system with a tankless coil to feed an aqua-booster. The boiler seems to be working ok but I don't want the tenant to have to worry about adding water if it gets low (which it sometimes does since the return of the water can be slow). Can I have an automatic water feed installed on this older system? Or, given the age, am I better off replacing the boiler?

Thank you in advance.


    JUGHNE Member Posts: 9,765
    A new boiler will not make the water return quicker. Actually it could compound your problem as it might contain less water in the boiler giving your system less water to work with and the boiler going off on low water and then an auto feeder would add water. Then when the cycle was complete and all water finally returned to boiler you would have too much.

    I would look for the problem of why the condensate is slow to return. If you have under floor wet return pipes or even if they lay on the floor, they could be partially plugged causing slow return. That problem should be addressed before anything, especially if you ever change the boiler. If the returns are dry, that is above the water line, then check the slope of drainage of the pipes. I did one system slope correction and gained almost 1 inch of water in the boiler. So if the piping is slow for any reason then an auto feeder might be overfilling the boiler.

    At best of course (and mandatory) is a low water cut-off control.

    When you lived there did you have to add water very often?
  • ishmael1980
    ishmael1980 Member Posts: 13
    Thanks for the information. There are return pipes on the floor so they may be restricted. I was also told that the two main vents are too small so I'll replace those as well. When I lived there I flushed weekly but every month or so the boiler would shut down for low water. I would bring the water back up to the proper level and the next day the pipes would start banging since the condensate came back and now the water level is too high.

    Would you suggest I replace the wet return pipes on the floor?
  • BobC
    BobC Member Posts: 5,308
    Those pipes probably have to be snaked out and flushed and you might end up having to replace them anyhow. You pays your money and makes your choices.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    Bob Bona_4
    JUGHNE Member Posts: 9,765
    As Bob said you may want to replace the wet returns. They may be original to the system and might have ignored with several boiler replacements. They are always full of water and probably the sludge from the years of accumulation. Depending on how large the radiation and piping is, the condensate will be slow to return anyway.
    If the return issues are resolved then the low water shut down may be avoided. The boiler would have to be blown down maybe every 2 weeks.

    I have had several rentals over the years, being able to stop in and visit the basement for necessary HVAC maintenance is a legitimate reason to be there. The tenants always knew I could call ahead and show up. Gives the landlord an insight to the condition of the whole house.
  • vaporvac
    vaporvac Member Posts: 1,520
    Definitely clean/replace the wet return. I was stunned at the grunge in mine! I was surprised the water ever came back.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • ishmael1980
    ishmael1980 Member Posts: 13
    Great! Thanks for the insight guys. Definitely helps.
  • RobG
    RobG Member Posts: 1,850
    To make replacement easier you can replace the return piping that is below the waterline with copper pipe.
  • Dave0176
    Dave0176 Member Posts: 1,172
    From what I understand that wasnt one of Weil McLain's best boilers, seemed to have been one of the worst to clean. And the single 2" minimum riser and header size all the way up to 740 EDR was just CRAZY. I just replaced a similar one, same issue with cleaning the flues, the boiler just ran high CO numbers because I could not get the thing clean.

    It looks similar to the modern SGO series of boilers.

    Wet returns are somtimes easier to replace then clean and snake, so I'm all for replacing it.
    DL Mechanical LLC Heating, Cooling and Plumbing 732-266-5386
    NJ Master HVACR Lic# 4630
    Specializing in Steam Heating, Serving the residents of New Jersey


    I cannot force people to spend money, I can only suggest how to spend it wisely.......