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Thread: Brew kettle ventilation question

  1. #1
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    Brew kettle ventilation question

    I am installing a 5 bbl brew kettle and the ventilation guys are suggesting to install a 1500 CFM fan (stainless steel). It has a manual "blastgate" and I can drop it to 600 CFM. I cannot control the motor speed.

    Is this suitable? Or is the fan too strong?

    Any help would be greatly appreciated.

    Charles
    cbierb@total.net

  2. #2
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    I think you will be pulling the kettle off the floor with that fan!

    Seriously--just VENT the kettle to the atmosphere, you don't need a fan for exhausting the kettle unless your vertical run is over ~20 feet.

    You could also condense the vapor stream with a simple water spray condenser. Route your Kettle stack to a drain right by the kettle. Plumb spray nozzles with 1/2 copper pipe into the stack. Use a ball valve to control the spray nozzle's flowrate. You neighbors will complain less about the smell, although there is a drawback of using more water in your brewery.

    B

  3. #3
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    Thanks.... but the exhaust for the kettle is only a couple feet high and goes straight out the side of building. Are you saying to not put a fan at all?

    I gather I would need some sort of fan but I wonder what would be the appropriate CFM. I was told that with 5 bbl kettle there would be about 70 L / hr of water vapour. None of the fan companies I talk to seem to know what strength to install.

    Any other comments or ideas?

    Charles

  4. #4
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    I would try it without a fan first, measure your rate of evaporation with water on;y, should be at least 4-5%.
    Linus Hall
    Yazoo Brewing
    Nashville, TN
    [url]www.yazoobrew.com[/url]

  5. #5
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    I'm inclined to agree with zbrew2k and lhall.

    However, there are some mitigations you can do you prevent problems with your current configuration:

    1.) Maintain an upward slope to the stack. Do not install it horizontally or worse yet, with a negative slope. Hot air rises and an upward slope will get you there. Come out of the steam spud on the top of the kettle with an adjustable elbow and get the best slope to the wall.

    2.) If you can't get a good enough upward slope (10 - 15 degrees is a great start......45 degrees is mucho better), run the stack outside vertically up to above the roof line. Attach a turbin vent "spinner" at the top. McMaster-Carr sells these in stainless for a modest price and they move some air.

    As far as CFM (but you quoted metric), I recently did some calculations for a stack scrubber a while back............At atmospheric pressure, 1 kg of steam will take up 1.67 cubic meter of space.

    1 kg of steam = 1 kg of water (logical)
    1 L of water = 1 kg
    So........70 L / hr boil-off = 70 kg of steam / hr = 116.9 cu meters / hr

    116.9 cu-meters / hr = 4128 cu-ft / hr, or 69 cu-ft / min (cfm)

    Which is a vigorous boil. We generate about that on our 7 bbl direct fire kettle with the 300K BTU warp drive on the bottom. Our boil is volcanic, to say the least.

    I'ld say that if you must, a 60 - 75 cfm duct fan will do it, but make sure the static pressure is LOW.........no more than 8 inches of water column. Yeah, I know, I mxed my units............never could keep my peas outa my potatoes.........
    Keep the static pressure low so as to not damage the kettle during cooling with the doors closed. 8 inches is quite low, and most squirell cage (centrifugal) fans can't pull that high anyway. That comes to less than .5 psi.

    Good luck!

  6. #6
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    Are they maybe talking about the vent for the gas burner? Mine has a fan to feed it, but nothing on the exit.

    Just a thought.
    Scott

  7. #7
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    Quote Originally Posted by Sir Brewsalot
    Are they maybe talking about the vent for the gas burner? Mine has a fan to feed it, but nothing on the exit.

    Just a thought.
    Scott
    When Charles talked about 70 L/hr of water vapor, I assumed it was the steam vent from the kettle itself. You raise a really good point, Scott........

    Which vent are we talking about, Charles? The combustion vent or the steam vent?

  8. #8
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    I was talking about the vapour from the boiling wort in the kettle... I am using a 5 BBL electric kettle.

    Apparently the "blast gate" can reduce the suction to about 200 cfm.
    Any comments?

    Thanks again,
    Charles

  9. #9
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    Quote Originally Posted by cbierb
    I was talking about the vapour from the boiling wort in the kettle... I am using a 5 BBL electric kettle.

    Apparently the "blast gate" can reduce the suction to about 200 cfm.
    Any comments?

    Thanks again,
    Charles

    Did you read my previous post?

  10. #10
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    Yes, I re-read your previous post.

    It seems to you that I'd need about 70cfm according to your calcuations, correct?

    So you feel that this is still too strong?

    Charles

  11. #11
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    Vent to the atmosphere! and be done with it. The laws of nature will take care of the rest. You don't need a fan. Repeat: You don't need a fan.

  12. #12
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    Charles,

    Not seeing your installation, I'm only guessing as to the ability to slope the steam vent out. I'm still in with lhall and zbrew2k. Initially, I don't think you need a vent fan..............providing:

    1.) The horizontal run is VERY short. Otherwise, slope upward.

    2.) You're not trying to pass it through a dryer vent on the side of the building........the vent duct will run up the side of the building.


    The critical operating paramters for a fan is a minimum of 65 cfm and no higher static pressure than 8 inches Water Column (WC) or so..........13 inches absolute max.
    The blast gate you mention will throttle down the cfm of the fan but will not reduce the static pressure. The "some is good, more is better" doesn't really apply here. You're only creating 68 cu-ft of expansion in the kettle in the form of steam. 200 cfm fans won't make it go away faster than a 75 cfm fan.

    If 200 cfm is the smallest you can find, certainly gate it down, as you have chosen, and watch that static pressure rating before you buy. You don't want to pull a big vaccum on the boiling wort (excessive foaming), nor do you want to pull a big vaccum on the empty kettle while it's cooling (deformation/warping possibility).

    And that's my story and I'm stickin' to it.

  13. #13
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    Thanks very much for all your input.

    Charles

  14. #14
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    Anybody else have any ventilation work that needs to be done? Sounds like Charles may have a company that is QUITE EAGER for work - maybe even creating some for themselves where it's not required?

    Doncha just hate that!

    S

  15. #15
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    One more thing is to make sure you can collect any condensation before it runs back into the kettle. You should have a lip and a drain on top of the kettle, or some other way to prevent the condensation, which tastes like super bitter creamed corn, from draining back into the kettle.
    Linus Hall
    Yazoo Brewing
    Nashville, TN
    [url]www.yazoobrew.com[/url]

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