Testing New Brewhouse Parameters - Boil Off Rate

Discussion in 'Homebrewing' started by BoardwalkBock, May 7, 2020.

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  1. BoardwalkBock

    BoardwalkBock Pooh-Bah (2,041) Aug 18, 2012 New York
    Pooh-Bah

    Hey all,

    So I’ve recently changed some of my equipment and have been testing parameters before my next batch. Tonight I was testing my boil off rate/hour when I got to thinking - how accurate can this calculation be for stove top brewing? For example, I put 3 gallons of water and starting heating the brew kettle on the stove top. Being that it’s not as intense a heat as using a burner outside, it takes longer to get to a rolling boil. However, parts of the water slowly boil faster than others before it’s a vigorous boil and water is slowly but surely evaporating. In some cases there are bubbles forming and steam leaving the kettle for 10-15 mins before the full boil starts.

    I’ve been measuring boil off rate/hour strictly from the start of a rolling boil as that is how I calculate boil time when doing an actual brew.

    Do you think the evaporation that occurs between the initial bubbles starting and a rolling boil is minimal that it doesn’t entirely matter? I calculated 0.80 G/hour tonight with this new system. I plan on testing again tomorrow as well. Should I possibly put this rate up closer to 1 G/hour?
     
    #1 BoardwalkBock, May 7, 2020
  2. VikeMan

    VikeMan Grand Pooh-Bah (3,067) Jul 12, 2009 Pennsylvania
    Pooh-Bah

    YMMV, but I think it's usually pretty insignificant. If you want to know for sure, test again, but remove from heat (and cover the kettle) as soon as the rolling boil starts. Then let cool and measure.

    How did you calculate it? By bringing it to a boil and then letting it boil for some amount of time? Then cooling, measuring, and subtracting from your starting volume? If so, then any pre-boil steam was already accounted for in your calculated boil off result. Given that I don't know why you would consider increasing your rate.
     
    #2 VikeMan, May 7, 2020
  3. billandsuz

    billandsuz Pooh-Bah (2,097) Sep 1, 2004 New York
    Pooh-Bah

    You might consider starting your measurements at 211 F. There is zero boil off at 211. At 212 let the boil off begin. This way you can calculate the actual vapor loss from an equal basis.

    Cheers
     
    #3 billandsuz, May 7, 2020
  4. SFACRKnight

    SFACRKnight Grand Pooh-Bah (3,348) Jan 20, 2012 Colorado
    Pooh-Bah Trader

    My wort boils at 196 and I am here to tell you I lose 1.5gallons an hour. I start to lose water around room temperature simple via evaporation. Bring humidity, outside temperature and barometric pressure into the mix and I can see as much as a .25 gallon change. Give me an air tight lid and a vacuum gun and I can make your wort boil off at room temps.
     
    #4 SFACRKnight, May 7, 2020
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  5. billandsuz

    billandsuz Pooh-Bah (2,097) Sep 1, 2004 New York
    Pooh-Bah

    Assuming your wort boils below 212 because of altitude the point is that it is still going to boil at a fixed number.
    I assumed that most of us could figure out that at any temperature less than boiling no boiling occurs, boiling being the way liquid turns to vapor and all that. I assumed too much apparently.:confused:

    So on your planet you lose a quarter gallon an hour due to humidity, altitude and the weather alone.
    Interesting. Your boil off calculations must be much more complex than using a watch and a thermometer.

    Cheers
     
    #5 billandsuz, May 7, 2020
  6. SFACRKnight

    SFACRKnight Grand Pooh-Bah (3,348) Jan 20, 2012 Colorado
    Pooh-Bah Trader

    My boil off rate can change up to .25gal depending on those factors is what I was getting at. Bring boil kettle geometry into it and it changes as well. My point is that your very specific measurements work for you but not everyone else.
     
    #6 SFACRKnight, May 7, 2020
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