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Lochivar - need help

way. Make sure the ground wire connected to the burner manifold is tight & in good condition.


  • dmy hvac
    dmy hvac Member Posts: 33
    flame failure

    i working on a lochinvar boiler model#cbn2065 that heats the commisary at fort drum ny via air handlers and baseboard.there is 2 boilers one lead and lag they were both not working i took both boilers apart and cleaned them boiler #1 was going off on low air found where pressure switch tube connected to burner was plugged cleaned it out now runs fine.boiler #2 going off on flame failure every couple days or so.now wont stay lit. i checked amp draw on ignitor old one was only drawing 3.1 amps and sometimes would not draw that much so i replaced it boiler doing same thing.does trial for ignition boiler fires for a sec sometimes then out all the book says is flame is detected by ignition module does anyone know where flame sensor is?i havent looked hard for it yet but i did not see one when i cleaned both boilers does anyone know how flame is detected?or suggestions?ill be going back tomorow would like to have both working cause could possibly be winter till july!dont think its a draft or air or gas pressure problem since its been running for years allthough if flame sensor is not problem ill be checking those things next. thanks for any help!
  • Rob L_4
    Rob L_4 Member Posts: 5
    Lochinvar-need help

    I have worked on some Lochinvars over the years. The hot surface ignitor is also the flame sensor on those boilers. You can also check the ohm's on a cool ignitor, it should be about 40-80 ohms room temperature. You should check the flow switch, sometimes they toggle back and forth and dont keep the boiler on. If that air switch tube was plugged, I bet the burners and heat exchanger is also caked up with the same stuff. You should pull that whole bottom door off(leave the burners on)so you can inspect the burners and heat exchanger. If they are caked up after two years you will get low air signals. Also check the draft. Even though it has been running for a few years, it could still be way off. After you have it all cleaned up, then you will need to set the fans and check all the gas valves for correct manifold pressure.
    Good luck, let us know what you find when you open those boilers.
  • dmy hvac
    dmy hvac Member Posts: 33

    thanks. have already completely cleaned that boiler was pretty much spotless usually gets cleaned every fall except for this year.that kinda screws up my theory with the flame sensor cause i just replaced ignitor.each pressure switch has a light that goes on if switch is not making and they all seem fine.are you sure all lochinvar units use hot surface ignitor i remember i have worked on other unit in past that did but that was a while back thanks again for any advice!
  • hvacfreak
    hvacfreak Member Posts: 439
    burner tubes

    The one thing that I KNOW about these is that the burner tubes must be clean. Any burner tubes that show distortion or warping need to be replaced , period.

    Correct gas pressure and clean burner tubes seem to be all Lochinvar boilers need to work well. A water hose with good pressure works well on cleaning the burner tubes. - M

    EDIT : And any I've seen used hsi.
  • John_86
    John_86 Member Posts: 7

    I was scanning the Wall and noticed your posting and the information the other Techs was providing. It is all correct. The boilers do need to be cleaned regularly, the HSI is the flame sensor, and usually one of those two causes flame failure. However there are other things you may check:

    Flame Failure can usually be narrowed down to a few common things:

    The boiler has a good flame but the ignition module can not see it. This can be checked by testing the flame rectification (micro amp) signal at the ignition module. It should be around 4 or 5 and it may bounce slowly about a .5 micro amp.
    HSI does not detect flame. Bad HSI or Ground.
    Ignition module receives a signal from the HSI but does not recognize it. Bad ignition module.
    Another not as likely issue is, air blowing around the HSI causing the flame to lift off the surface of the HSI. Check around the mounting surface of the HSI and front cover ensuring the surfaces meet.
    Plain bad combustion. Again checking flame rectification it may be erratic, or never gets above .5 – 2 micro amps.
    Dirty Burners.
    Dirty Heat Exchanger
    Incoming gas pressure
    Manifold gas pressure
    Combustion chamber pressure.
    Burner pressure.

    Air and gas settings and draft are very important as the gas valves operate like a regulator. The valve wants to maintain 3.4 – 3.8 inwc manifold pressure, it does not sense where it comes from. So if air pressure is high the valve will limit the incoming gas. If the air pressure is low it will allow more gas through, again it wants to maintain a constant manifold pressure. If your draft is erratic it will affect air pressure, which affects gas pressure, which affects the flame rectification signal, which may cause the boiler to trip.

    Connect a draft gage to the stack, a monometer to test incoming gas, connect a manometer to the manifold gas pressure tapping, and finally a test meter to the ignition module to check flame rectification. Start the unit typically you will find the answer fairly quickly or at least narrow it down to an electrical issue.

    I hope this helps. It sounds like a lot to check but it is fairly straight forward. If you run into any trouble please feel free to call Lochinvar Tech Service at 1-800-722- 2101.

  • tim smith
    tim smith Member Posts: 2,752
    Lochinvar boiler info

    Make sure when you clean the burners that you remove them and wash them out, flush with water. This is a tube in tube design burner and gets dust and particulate inside between the tubes and distorts flame. Also make sure heat exchanger is fully cleaned and not just surface brushed. Sounds like you already got the igniter info. Ground important as stated above. Good luck, Tim
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