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Troubleshooting input requested: New boiler replacement, radiator vent spewing water

First time poster, but I did study through the Lost Art of Steam Heating prior to posting, and have tried my best at troubleshooting potential causes. Hoping the experts can provide some input so I can speak with the contractor more intelligently.

2 bedroom single family house, new Peerless EC-03 oil-fired steam boiler replacement due to old leaking boiler. See pictures for before and after. Old system wasn't perfect (clanging, malfunctioning radiator vents), but no water was coming out of vents.

The 29" height marker in the picture feeds the first radiator on the second floor, which is spitting/venting water out of the radiator vent. All remaining radiators are fed through the higher mains, and don't have any water issues.

Suspected root cause
New boiler is taller than previous, and distance from water line to first radiator line has been shortened. As a result, wet steam/water is making its way into the first radiator line. Contractor has suggested re-locating the first radiator line into the higher main line, but they never mentioned the need for this prior to starting the job and giving us the quote.

What has been tried/checked
Pressuretrol: ~0.75 psi + 1 psi differential, OK.
Distance from WL to first "header" (marked in picture): 29", >24", OK.
Distance from WL to lowest horizontal drain line (not marked in picture): ~26", >18", OK.
The near-boiler piping is taking a number of additional turns compared to previous piping, not sure if this can cause issues.
I have not calculated the combined EDR or compared with the boiler rating to check if it was sized correctly.
Contractor downfired the boiler, which appears to have solved the water-spewing issue. But I don't want to run at a sub-optimized power or consume extra fuel unnecessarily.

What do you all see from the pictures and the information I've gathered? What am I missing?


After, with measured dimensions

After, another view


  • Dan_NJ
    Dan_NJ Member Posts: 247
    edited December 2021
    Not a professional here, but the first things that jump out are:

    1. Gatorade colored water in the boiler - there is some additive in there.
    2. Equalizer looks to be 2" - same size as the single riser and the header- and should be 1-1/4" per install guide linked below.

    Does it surge at all when running? Has it been skimmed one or a few times? Has it been run on plain water with no additives and if so how does it perform then?

    The height seems pretty close based on the pictures but it's hard to tell without actual measurements before/after.

  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    Heights are really tight... is there any drip or way to drip that one misbehaving radiator line (frankly, I don't see one -- but thought I'd ask). It would be awfully tight to tie it into the higher steam main line. Not much length in there to play with.

    Let me think.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,061
    edited December 2021
    You could crack or unscrew the first 90, replace it with a tee and have a drip line.
    Union is helpful there. May have to drop the flue piping giving it more slope anyway.

    Note: by the first picture it looks like enough clearance for the tee without moving the flue pipe.
  • delcrossv
    delcrossv Member Posts: 742
    edited December 2021
    Sounds like you're pushing water up into the mains.

    It's not an equalizer size issue. You can make those too small, but there's not a real upper limit.

    This looks like the ideal situation for a drop header. Take the riser almost to the ceiling and drop down to the header (larger than the supply size), then take the two mains off with separate tees.

    If you used the front tap on the boiler you'd miss the flue entirely.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
    EBEBRATT-Ed Member Posts: 15,529
    Even though it was not done with the old boiler you have 2 main supply pipes. They should have been connected to the boiler header separately. Too much velocity is producing wet steam

    If the boiler was never skimmed on start up (it should have been) putting treatment in will not fix a surging issue
  • bairice
    bairice Member Posts: 8
    Thanks everyone - I was thinking about a drop header too, will need to discuss with the contractor and figure out the optimal configuration within the geometric constraints. Maybe there's a way to tie a drip line exiting from the lower main.

    I did note the large equalizer but my understanding is also that it's typically an undersized equalizer that causes issues, not oversized.

    I don't think there was any surging, but I'll also confirm if they skimmed the boiler upon installation and ask them to try that again regardless.
  • neilc
    neilc Member Posts: 2,703
    any idea of the BTU or EDR size of the old boiler ?
    and what of this one ?

    did the installer measure your radiators before choosing this boiler ?

    loose the green water and refill with fresh clear water,
    if this doesn't calm down the spitting,
    then maybe you can down fire the burner,

    post a picture of your main vent
    known to beat dead horses
  • bairice
    bairice Member Posts: 8
    edited December 2021
    I'm going to hold off on draining the treated water -- the contractor said they would come back so I want them to continue their process and figure out the piping.

    Boiler is rated for 90000 net BTU/hr, 375 sq ft EDR. It's currently downfired so probably somewhere lower towards 68000 net BTU/hr. I'm not sure if they did a EDR analysis to size the boiler (will need to check), nor have I tried doing the sizing myself to verify. Not sure what the previous boiler ratings were.

    I tried to trace to a main vent and pretty sure this system doesn't have one. Shown in the picture, the higher horizontal main feeds a number of the radiators, and then loops backwards to the wet drain, no vents to be seen. Obviously there should ideally be a vent, but does this explain the water symptoms I'm having if the other radiators are otherwise venting and heating sufficiently? Probably not optimal, I'm sure.

    This was my vision for a drop header geometry, from a side view, which I believe would be one way to alleviate the issue.

  • neilc
    neilc Member Posts: 2,703
    draw in the 2nd boiler riser,
    and a new equaliser

    you need venting on that main, either out at the end loop,
    or before you drop down the the wet return,

    lose the coolaide
    known to beat dead horses