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Closet Boiler Venting Into Alley

I'm looking for some guidance on replacing a Burnham Spacemaster direct vent gas boiler. We have hydronic baseboard heating and the options considered have been in the 90,000 to 100,000 BTU range.

The current boiler is in a very small closet (25 inches deep, 34 inches wide, 106 inches high) in our second floor condo in New England. It vents into an alley that is 55 inches wide with more units (and windows) on the other side and above. The alley has a dead end at the end closet to the vent, which means the current location is near a corner.

Our plumber was preparing to recommend a high-efficiency condensing boiler, but the manufacturer had concerns about wind causing air intake problems since it is located near a corner in an alley. I'm also worried that the visible plume will be visible from any window facing the alley in the winter and could be a nuisance for units above us and across from us. As a result, the manufacturer recommended rerouting the vent through the roof. However, that is not an ideal option since there is another unit above us.

Given those challenges, our plumber is currently looking for a conventional (e.g. non-condensing) direct vent boiler that could vent into the alley at the same location since this type of boiler has been fine venting there in the past. However, from my scan of potential options, it seems that none currently on the market will fit into the closet.

Any thoughts on next steps? Are there conventional direct vent options that would fit that I have not come across? Is there another way to tackle this problem? Or should we just move forward on a high-efficiency condensing boiler and vent through the roof?


    HVACNUT Member Posts: 5,863
    Do you have to go through a co op board to do this work? I'm sure its come up before.
    As you found out, manufacturers have very specific guidelines for venting and combustion air.
    I would check with the board or neighbors.
    What are you using for domestic hot water?
  • CondoChallenges
    CondoChallenges Member Posts: 2
    edited April 2019
    Each unit has a separate hot water heater in the basement for domestic hot water. We live in a very small condo, so there isn’t anything as official as a board. Most of the boilers haven’t been replaced in 15-20 years (and the one that was replaced in the last 10 years was swapped for another direct vent that is no longer in production) so they are all still venting into the alley. Will definitely follow-up with the neighbors, but had hoped to find a way to save them some trouble (and save us the extra cost of going through the roof).
    HVACNUT Member Posts: 5,863
    edited April 2019
    Even if the boiler is in a closet, can the venting run at a pitched horizontal on an interior wall, then terminate to outside to get away from the inside corner of the building?
    Where do the bathroom exhaust, range exhaust, exit?
    If there's a common chase to the roof, maybe... a concentric out the roof.
    But all must meet code and manufacture specs.
  • Jamie Hall
    Jamie Hall Member Posts: 23,436
    Check the maximum duct length distances and elbows -- can you go far enough to get up above the top of the alley running outside?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,620
    I believe Weil McLain CGI would work
  • PRR
    PRR Member Posts: 156
    edited June 2019

    ...New England. ...condensing boiler... air intake problems since it is located near a corner in an alley

    Go up high. My problem is the pipe comes out near the ground and has to get well above the snow. That works out face-high, which would hit me when I mow, so ran it over my head.

    Do read your Manual. But it looks to me like a 110kBTU burner can run 20+' in 2.5' pipe, or 8 stories in 3"pipe, assuming just a few elbows.

    Then something like this:

    You need permission to screw to the upstairs neighbors' outside wall. You need a tall ladder and the bravery to work up high.

  • Intplm.
    Intplm. Member Posts: 2,006
    And some companies make a vent snorkel. Will that help or be able to be applied here?
  • Ironman
    Ironman Member Posts: 7,379
    Take a look at this:

    I seriously doubt that a small condo needs more than 30k btus unless the boiler is heating domestic also (combi). Over-sizing a boiler is NOT a good thing.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    Is this natural gas or LP? Electric (gulp) boiler may be an option with such a tiny load. Or go for the roof! Many mod/cons can go upwards of 80 feet of equivalent vent length.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!