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Malibu oil fired boiler undersized nozzle?

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DTracy80
DTracy80 Member Posts: 4
in THE MAIN WALL

hi all, I have a Malibu oil fired cast iron boiler rated for 2.5 gallons an hour. 244,300 btu. I just purchased this property and I’m wondering if the nozzle is way undersized. it and it says .85 GPH. Even at a higher pressure, let’s say 150 psi which im not sure of, it still seems way under capacity. There are seven zones connected to this boiler and it’s set at 185 but it seems to run about 20 hours a day. Any advice would be appreciated.

IMG_4366.jpeg IMG_4263.jpeg IMG_4262.jpeg

Comments

  • MaxMercy
    MaxMercy Member Posts: 574
    edited January 27

    If it's 240K BTU, it's way underfired, maybe by half. Other than it being inefficient, I would also be concerned with condensation. I'm sure someone here can give you appropriate nozzle size and pressure. [EDIT] - download the manual for it - https://www.freeboilermanuals.com/assets/pdf/SlantFin/Malibu.pdf

    The manual says 2.5gph 80° solid for that model, presumably at 100lbs, but even at 200lbs, a .85 is only 1.2gph.

    I wonder if it was installed by mistake.

  • HydronicMike
    HydronicMike Member Posts: 300

    There's not enough info. We don't know how the burner is set up, what burner is even on it, what are all the combustion numbers. You don't even know the pump pressure.

    1. Why did you pull the nozzle?
    2. "Seems to run 20 hours a day" isn't really helpful. If it's close to design day, it might be running as expected.
    3. You need a proper oil burner tech to come over there, check everything and address your concerns.
    4. It's possible there's not enough water in the boiler, aquastat settings or wrong, a circulator isn't working or some other problem with your system.

    No one can guestimate your problem over the internet with this very little information.

  • DTracy80
    DTracy80 Member Posts: 4

    the house is maintaining 70°, pressure is at 18 psi. I’m just thinking that the nozzle is undersized for the unit. I pulled it just to check what size it is. Temp goes up to 185 and shuts off until it hits 165. the circulator does work and all radiators are getting hot.


    I put a hour meter on the boiler to see how long it is running per day and I’m guessing it’s about 1 gallon per hour with the current nozzle.

    Everything seems to work fine. My only concern is the nozzle is under sized and the boiler is running way too long or would be much more efficient with a larger nozzle getting up to temperature quicker. No leaks anywhere and pressure is constant at 18 psi hot. No black smoke out the stack or anything like that

  • Steamhead
    Steamhead Member Posts: 18,330

    The boiler might be oversized and that's why it was down-fired. Need to do a heat-loss calculation on the building to verify this.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • DTracy80
    DTracy80 Member Posts: 4
    edited January 27

    the house is 7000sq feet so 250k btu sounds right to me.

    I’m wondering if someone installed the .85 nozzle in an attempt to save on oil?

  • HydronicMike
    HydronicMike Member Posts: 300

    All your doing is guessing. You need to test. If your burner keeps running up to high limit and shutting off, it's still oversized. And again, you don't know the pump pressure or any of your combustion numbers.
    So unless you want to get a competent oil burner tech in there, how is anyone going to help you?
    .85 @ 100 psi =.85=111,887 btu's gross for straight USLD

    .85@ 160 psi=1.08 gph=149,785 btu's gross for straight USLD
    That's quite a difference. Keep goofing around…

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,947

    Could be a 1.85 gph nozzle

  • DTracy80
    DTracy80 Member Posts: 4
    edited January 28
    https://forum.heatinghelp.com/discussion/comment/1884570#Comment_1884570

    all I’m asking is if a .85 nozzle in a 2.5 capacity boiler is acceptable and commonly done.

  • HVACNUT
    HVACNUT Member Posts: 7,326
    https://forum.heatinghelp.com/discussion/comment/1884693#Comment_1884693

    Of course not. But if it were mine, I'd ride it out and plan on replacement with a proper sized boiler. It makes limit on what seems to be a design day, correct? Just do the math now so you know what you need when you decide to upgrade.

    MaxMercy
  • HydronicMike
    HydronicMike Member Posts: 300
    https://forum.heatinghelp.com/discussion/comment/1884693#Comment_1884693

    Without knowing anything else, it's impossible to answer that question. Some boilers can be configured for multiple firing rates and set ups, and again, without knowing the pump pressure you don't know your input.
    It's probably wrong, but you just can't change it without knowing what you are doing and how to properly test combustion.

    MaxMercy
  • MaxMercy
    MaxMercy Member Posts: 574
    https://forum.heatinghelp.com/discussion/comment/1884511#Comment_1884511

    I'm really curious what your stack temperature is with a boiler that big and a nozzle that small,

    HVACNUT
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,947

    It would be very unusual IMHO for a boiler rated to fire 2.5gph/hr to run with a.85 gph nozzle as @HVACNUT mentioned

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