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Split Flue

Dan Foley
Dan Foley Member Posts: 1,260
in Strictly Steam
I looked at this one today. It was a survey and estimate to replace a steam boiler in Silver Spring, MD. This is on a 2-pipe system. The home was built in 1928.

I have never seen a flue pipe split and vent up two separate chimneys. The home inspector red tagged it. Is this a code violation? I could not find anything in IMC or NFGC but maybe I missed it?

Comments

  • Ironman
    Ironman Member Posts: 7,510
    I've never seen anything like that. Maybe someone replaced two boilers with one?
    I don't need to tell you that those two smaller vent pipes do not equal the capacity of the large one on the boiler.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    ZmanDan Foleydelta T
  • JUGHNE
    JUGHNE Member Posts: 11,248
    It must have been easier than chopping into the masonry.
    Looks like a lot of boiler, perhaps replacement will be smaller.

    Is this a 2 pipe counter flow system?
    I have seen one in place but never in any books.
  • Zman
    Zman Member Posts: 7,610
    One thing for sure, you will never get a manufacture to sign off on that for the new boilers....
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Dan FoleyIronman
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,252
    Well, that's a new one!

    I will bet you won't find it in any code book either.

    Things get added to code books when people do stupid things.

    The electrical code never use d to prohibit CB panels mounted in a ceiling. They do know because somebody did it
    Dan Foley
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    I just finished reading the IFGC codebook preparing for master test and I don’t recall seeing anything related to this. I will check again tomorrow.
    Never stop learning.
    Dan Foley
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    That is god d@#m ridiculous. It actually makes me angry.

    There was an error rendering this rich post.

    Dan Foley
  • Fred
    Fred Member Posts: 8,542
    It looks like the gas pipe goes into the middle of the burner as well, with 10 tubes on one side and 8 tubes on the other. I wonder if this is two (modular) boilers with a separate flue for each side?
    Dan Foley
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,207
    edited June 2019
    Bad perhaps, but it looks as though it's been there awhile without any expected flue or boiler deterioration.

    Is there a spill switch on the draft diverter?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • BobC
    BobC Member Posts: 5,495
    The near boiler piping is pretty bad as well, I'd not be surprised to hear they were having problems with fuel consumption and heat distribution.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Dan Foley
    Dan Foley Member Posts: 1,260
    Thank you for the observations and comments. This boiler is 30-35 years old and grossly oversized at 500k input.

    It is 2-pipe but not counterflow. The main vents have been removed and plugged. There are presently no vents on the system.

    If I get this one, I will dig a little deeper for more information and answers.
  • Bob Harper
    Bob Harper Member Posts: 1,083
    edited June 2019
    The vent connectors are SEVERELY undersized for 500 MBH input. This is not addressed in NFPA 211, '54, '31' or IFGC because up to now no one has been this stupid and desperate.
    Reline the biggest flue then work backwards and calculate the maximum input for that liner and that's the maximum size boiler they can install unless they go modcon out the sidewall.
    Mike_SheppardDan Foley
  • Steamhead
    Steamhead Member Posts: 17,312
    How much EDR on this system?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steamhead
    Steamhead Member Posts: 17,312
    Bob Harper said:

    ............unless they go modcon out the sidewall.

    Not on a steam system.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • ScottSecor
    ScottSecor Member Posts: 887
    My guess is neither chimney has the capacity to carry the flue gases (as others stated) by itself. I'm wondering if the house used to have an oil fired boiler that was set up for forced draft, not recommended for a building with a typical thirty foot tall masonry chimney. In some instances we prefer the simplicity of the atmospheric boilers but cannot use them due to chimney constraints (this may be one of them).
  • Bob Harper
    Bob Harper Member Posts: 1,083
    Steamhead said:

    Bob Harper said:

    ............unless they go modcon out the sidewall.

    Not on a steam system.
    Oops! Wasn't paying attention.
    Well, in that case if you REALLY need all that heating horsepower and have two skinny flues, you would be limited to two smaller boilers that would mate with the largest liners that would fit those rough flues.
  • gerry gill
    gerry gill Member Posts: 3,078
    Whats the draft readings? Everyone is quick to jump on it but i want to know first if it drafts? Does it spill any on a smoke test etc.
    gwgillplumbingandheating.com
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Dan Foley
    Dan Foley Member Posts: 1,260
    Gerry,

    No tests were done. This was strictly a visual survey and estimate. It is 30+ years old so it drafts.

    It’s moot point because it will not pass WSSC inspection like this. A liner is required.
  • gerry gill
    gerry gill Member Posts: 3,078
    So whats the plan Dan? two liners, two boilers properly sized Like Bob says?
    gwgillplumbingandheating.com
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Dan Foley
    Dan Foley Member Posts: 1,260
    The plan: have the chimney inspected by a licensed chimney contractor.

    Ideally one boiler and one liner, if the flue chase is big enough. The house does not need a 500k input boiler. I will measure EDR and size accordingly.
  • gerry gill
    gerry gill Member Posts: 3,078
    Are you thinking also about bouncing the EDR number in each room off the heat loss as it exists today?
    gwgillplumbingandheating.com
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

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