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Brew kettle not coming to a boil!

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  • Brew kettle not coming to a boil!

    Tried to get this new fabricated make shift kettle to boil water and couldn't get past 208 degrees after 4 hours. What is wrong here?

    Couple of things to consider:

    1) Kettle is 5bbl capacity
    2) Direct fire - burner is up to 325k BTU - lots of heat
    3) Kettle is thin single walled.
    4) SS skirt surrounds the bottom
    5) Middle of the kettle is a 5 in burn pipe/exhaust flue with an adjustable damper.
    6) Exhaust fan above pulls steam/vapor out through the roof.

    Any tips/tricks/thoughts are appreciated!

    Sorry, can't get the photo turn right side up!
    Attached Files

  • #2
    A couple of things are probably wrong, not the least of which is your flue coming straight up the center of the kettle. Looking at your damper, id say you are loosing a ton of heat straight up that pipe, a much smaller surface area than the bottom of your kettle. You need to have your skirt come up the sides of your kettle and have the flu gasses flow around the kettle. The side skirt would have the flue gas entrance on one side, the flue exit on the side 180 degrees opposite. This will give you better efficiency in the kettle because it will keep the heat in contact with it longer.

    A second thought, you say that you have a 300,000+ btu burner, I have a 400,000 btu burner that I run at 18% of maximum fire to maintain a boil in my kettle. I would guess that you are not getting the btu you think you're getting. What kind of burner do you have? Forced air or a jet burner, what is your gas pressure at the inlet to the burner? If you can't measure these, have a plumber or a boiler tech come check it. Super important to make sure you're not running really lean or rich.

    As an example of an efficient kettle, ours runs with a 400,000 btu forced air burner, we run at 18% of maximum fire, minimum is 20,000, so our actual rate is 88,400 btu/h. Ive verified this by clocking our gas meter. Our firebox covers the whole bottom, plus about 1/3 of the side of the kettle. Were a 10bbl kettle. Flue gas temperatures leaving the fire box are 300 degrees F, which is really good.

    So where should you go from here, first thing, check your gas pressure and flow rates to the burner to verify that you are getting the heat you need. The next thing would be to dump that center flue, and put it on the side, with some fire box that extends up into the sides of the kettle. Obviously, this is more expensive of a fix than I think you would want to hear, but I think its really important. I think you will scorch your wort like crazy with a stack like that.


    • #3
      Thanks for your reply!

      Without the added vent pipe in the middle of the kettle, we were running way too rich. The bottom of the kettle was a blue blob and not enough oxygen. Now it seems like all the heat is escaping. I closed the damper and still took hours, and not even got to boiling temp.

      We have plenty of gas pressure based on our gas meter.

      Makes sense with what you're saying though.


      • #4
        A good A/F ratio will yield a blue flame. Are you using a jet burner or something? Those are not the best for such large kettles, but they will work if they are sufficiently far away from the bottom so they don't make lots of little hot spots. A lean flame is is usually very small and blue/violet, rich flames are yellow with lots of carbon, good flames are a clear blue, with possibly some red/orange tips.

        How far away from the kettle is the top of the burner? You probably will need at least 12 inches.


        • #5
          Yeah, it's a jet burner (natural gas). It's about six inches from the kettle bottom.
          Attached Files


          • #6
            Another photo of the kettle. Any and all input is appreciated.
            Attached Files


            • #7
              Just looking at that photo, with the burner 6" away, the flames are going straight up the pipe only, nowhere else. Back that burner away from the bottom of the kettle and close that flue damper, you will get more heating of the entire firebox. You're probably loosing 90% of your heat straight up that pipe without even putting much into the water.