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Negative Building Pressure Effects on Category IV Boilers?

RyanO Member Posts: 4
There is a particular boiler manufacturer who is claiming that a slight negative building pressurization has led to a cracked on a cracked heat exchanger on a 2 Million BTU, Category IV Condensing Boiler. Anyone have any experience with this? The negative condition exists but the boiler is sealed combustion and has had no flame failures. It seems to me that if the building pressurization was effecting the boiler then there would have been a flame failure.


  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    I would ask for the technical data from the manufacturer which supports such a thing happening. I have over 50 years in the business and have had a lot of strange things happen but this would be a new one for me. I have had many a boiler with negative pressure in the building but can't say I ever had it cause a cracked boiler.

    What is the make and model of the boiler?
  • kcopp
    kcopp Member Posts: 3,819
    Sealed combustion is just that...sealed. Intake air should negate any negative pressure in the building..... isn't that the reason you have sealed combustion????
    I would love to know what Mfg. this is.... I could guess , but I will not.
  • BobC
    BobC Member Posts: 5,228
    All the hot air from the debates causes thermal stress and that will void the warranty.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • njtommy
    njtommy Member Posts: 1,105
    I'm going to guess its an Aerco benchmark 2.0.
    I would doubt that the pressure in the building has anything to do with the boiler have a bad heat exchanger.
  • Gordy
    Gordy Member Posts: 9,514
    How hard have you followed up on this?
  • RyanO
    RyanO Member Posts: 4
    First off... definitely not my boiler. I'm retro commissioning a 10 Million BTUH boiler plant (and the rest of the BAS/HVAC system) with issues and the manufacturer is using the building negative an escape clause for warrantying the HX. kcopp, I totally agree...that's why I came to The Wall. BTW its a Camus.
    There are 3 Condensing (Cat IV) and 2 Non-Condening (Cat I), all 2 MBTHU, same make. They share Combustion Air Ducting with isolation dampers. They are flued separately. This was a public project, so I really think the design engineer needs to step up. Of course everyone is pointing fingers and no one wants be accountable or working towards a solution. Nevertheless, I'm determined to find a solution for them.
  • Steamhead
    Steamhead Member Posts: 14,837
    Check out this thread that references Camus. The last few posts might explain some of what you're experiencing...............
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • RyanO
    RyanO Member Posts: 4
    Thanks, Steamhead! They're DynaFlames also. Maybe its a metallurgic design flaw.
    Tim, I'm at least the third guy on the scene here. No as-builts, no start-up docs. Could the combustion air be too cold? If only one of the 5 boilers is running and the other dampers are shut its almost like the 7 times rule backwards but with suction pressure. But then again I would think the burners would love cold air.
    I told the Town's Engineer that he needs to hold their feet to the fire. They being: the design engineer, boiler installer, and Camus to make this right for them. I recommended the same thing you did. Call Camus and make them explain how the negative building pressure effects sealed combustion...