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Mod Con appropriate replacement for single pipe steam?

DRod_3 Member Posts: 10
My Weil McLain boiler is about 30 years old, but still working well.  I'm guessing about 80% energy efficient.  Probably a bit oversized as on chlly days (not cold), second floor radiators barely get warm before system shuts down on temp, at thermostat (on main floor).  All rooms heat great on cold days (when system actually builds some pressure and cycles on vaprorstat/pressure).  . 

Anyway, should I consider, if and when I replace my boiler, a modulating condensing unit, or is that not a good application for single pipe steam?   


  • gerry gill
    gerry gill Member Posts: 3,078
    no its not.

    A mod con is a water boiler....not to mention a maintenance headache ;0
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • replacement choices

    as gerry has said, a mod-con boiler is for hot water only, so your best bet will be a new steam boiler, which has been sized to the number of radiators and their capacity [edr]. your present boiler may or may not be over-sized, but all radiators should get steam at the same time.

    now let's guess why your system does not warm properly on the second floor.

    this could be lack of main [not radiator] venting, or a wrongly set up, or located thermostat.

    post some pictures of your main vents, and tell us what thermostat you have.--nbc
  • DRod_3
    DRod_3 Member Posts: 10
    More info on my system

    I've got two mains/returns, with three Gorton #1's on one, and two Gorton #1's and one Hoffman on the other/second main return.  One main serves the front of my house (first and second floors), while the other main serves the back of my house (again, first and second floors). 

    The mains heat at the same time, The vaporstat is set at lowest settings and for the most part shows no pressure building (I have my gauge in ounces) except for very cold days when it will cycle on pressure. 

    My main floor has six radiators, ranging greatly in size.  One had been replaced and is a cast iron base board (in the kitchen).  The vast majority of the radiator "space" is on the main level.  Upstairs, I have 4 radiators, one in each bedroom and one in the up bathroom. 

    In general, everything works well, except on milder days when the heat kicks on and heats the main level slightly--to temperature on thermostat setting, with no real heat getting to the second floor.  Once it gets colder, everything heats very well. 

    I was a strong reader of Heatinghelp.com a few years ago and upgraded my system with your help. Back then was when I added the multiple main vents, Adjusted my thermostat setting so it wouldn't cycle as frequently as it had been.  Made sure my Vaporstat settings were lowest possible (can't adjust any lower).  And, I replaced all my radiator vents with updates per the guidelines---mostly Gortons. 

    I have to admit, following the recommendations of sizing the radiator vents to the radiator size sounded like a good idea, and that's what I initially tried.  But it really caused issues for my second floor radiators---they were very slow in heating, so I put faster venting Gortons on the upstairs radiators.  This improved performance dramatically, but still not great in mild weather.  Also, I made sure all radiators were pitched correctly. 

    I've thought, as is suggested above, that my thermostat is not in the ideal location----it's in the main floor dining room, which tends to be warm.  It would be better if it were in an upstairs bedroom or hallway, I think.  That being said, it still doesn't answer why my upstairs radiators are slower in getting steam during mild weather. 

    I'll post some pictures soon.

  • Jamie Hall
    Jamie Hall Member Posts: 22,937
    Seems to me

    that you've done about what can be done -- mild weather is the most difficult situation to get a steam system to work evenly in, as any little variations in timing in getting steam to the radiators is just going to be magnified by the short "on" time of the boiler.  I rather doubt that there really is a difference in how long it takes steam to get to the various radiators in cold vs. mild weather -- it's just that you notice it in mild weather.  Other than slowing the ground floor radiator venting even more, I honestly doubt that there's all that much more that can be done -- and even that may not be a good option.

    Sorry to sound unhelpful...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • DRod_3
    DRod_3 Member Posts: 10
    Thank you and one more question...

    Thanks, Jamie.  I thought it may have been optimized with what I'd already done.  The only thing that still comes to mind is if one of the runs had dropped a bit---not sure how that would have happened, or considering how well all rads heat in very cold weather it may likely not have happened.  What I thought I might try is elevating one of the upstairs radiators a bit, the one farthest out/away from the boiler.  I'd still keep the pitch, just elevate the whole unit a bit by putting something under each leg.  If its run had dropped a bit, might that help fix it?  Just a last ditch thought. 
  • David Nadle
    David Nadle Member Posts: 624
    One more thing to try

    You might try faster vents + TRVs on upstairs radiators. The faster vent will bring more heat upstairs in milder weather, and the TRV will prevent overheating on cold days.
  • DRod_3
    DRod_3 Member Posts: 10
    Thanks for the suggestion, that may be worth trying.

    I could do that to one or two of the four upstairs rads to see what kind of difference it makes.  Then, if successful, I'd do to the remaining.  Any reccommendations on the brand of TRV's?  I've never used or installed them, but know a little bit about them. 
  • David Nadle
    David Nadle Member Posts: 624
    Danfoss RA2000

    If the air vent on your radiator is not covered or obstructed I would go with the basic Danfoss RA2000, the one-pipe adapter, and a straight Gorton C or D vent. If your existing vent is very slow you might only need to go a little faster, like a Gorton #6.

    If you have wood radiator covers you can get the remote dial/sensor combo and mount it on the outside of the cover through a 3/4" hole. If you have curtains, etc, the remote sensor model is best but hiding the capillary tube can be a challenge.  

    I love the idea of doing the radiators one at a time because you never know what's going to happen and if you change too many things at once it's hard to troubleshoot.
  • crash2009
    crash2009 Member Posts: 1,484
    During the swing season

     those days where the boiler stays off for long periods of time.  I have a similar situation to yours.  The boiler only comes on for a short time, and this is not enough for the farthest rads.  I have been using the anticipator setting on the thermostat, to force the boiler to run longer and more frequently.  Also I adjust a window close to the thermostat.  As winter progresses, the crack in the open window gets smaller, and the anticipator gets farther away from 1.2 (1.2 is zero anticipation)

    I doubt that what I do is energy smart, but it makes things more comfortable without doing and undoing a bunch of changes to the existing venting. 
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