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Thread: Corretto vent hole size and ensuring bread maker doesn't overheat

  1. #1
    Senior Member ozscott's Avatar
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    Corretto vent hole size and ensuring bread maker doesn't overheat

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    After doing non lidded roasting for some years I decided to go closed again mainly due to ease of roast control but also due to my electronic Bosch heatgun overheating and turning itself down (which isn't fun mid roast).

    I made a lid from 4mm alluminium plate. The hole for the heat gun just allows the heat gun to pass through with a mm or 2 clearance around it. The vent hole is half that size.

    The bread maker overheated and shut down its agitating cycle just after the rolling first with a nice 3 degrees C climb going on. Very disappointing.

    So first up I am going to wrap the pan with my fire blanket (I used to use it but it would are at times when lifting it out so I stopped). I am looking at doubling the vent hole size. I could probably also run a 2 to 3mm plate of alloy down the inside of the breadmaker to shield the electronics where perhaps the overheat sensor is located.

    Any thoughts? How big a vent hole have people found effective at keeping thermal efficiency but allowing enough ventilation to keep the bread maker content?

    Cheers and thanks

  2. #2
    Mal Dimal's Avatar
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    G'day mate...

    Yes the exhaust vent should be roughly half the radius greater in size, than the internal radius of the heatgun nozzle.
    This will ensure much less resistance to the flow of gases.

    Mal.
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  3. #3
    Senior Member ozscott's Avatar
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    Cheers Mal. Knew you would know the answer. I will drill another vent hole the size of the hole for the heat gun, near the first hole. That will give the total.vent size along the lines you are recommending Mal if my maths is right.

    I'm excited about getting the lid right. Small pleasures. I thought about TIG welding up a holder out from the lid for the heatgun but my existing set up (a home brew bottle capper) works fine.

    Cheers
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  4. #4
    Senior Member Yelta's Avatar
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    Morning Ozscott, I did a lot of experimenting with exhaust hole size early on in my roasting days, gradually increased the size until I reached what you see below, approx 1/3rd the area of the top of the bread maker worked very well in my setup, have been using it ever since with excellent results.

    Another point worth noting, We spent Christmas with my son in law, also a Coretto roaster, he told me his Bosch heat gun was causing problems, can not adjust the heat up or down, I watched him do a roast, his gun was covered in smoke residue and the vents were constantly getting clogged with chaff, the main difference in our two setups is I use a pedestal fan directed directly at the roaster during the whole of the roast cycle, it blows smoke and chaff away from the gun, my Bosch is still running without problem after 10 years of roasting, his is failing after about 2 years of intermittent use, its important to keep heat gun vents clear and I suspect smoke/roasting residue has found its way into the heat control rocker switch on his gun and is causing problems.

    I see the fan is an important part of my Coretto, they are cheap, $10 at the likes of K Mart.
    DSC_0276_1000x669.jpg
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  5. #5
    Senior Member ozscott's Avatar
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    Behmor Coffee Roaster
    Thanks Yelta. We have the same gun. I have always run a fan. Blasts the heat gun vents. I stopped using it for a few roasts some time.ago (used the fan elsewhere for a bit) and that was a mistake.

    Cheers



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