farmroast Senior Member Joined: 13 Jul 2006 Posts: 1,417 Location: Amherst MA. Expertise: I like coffee
Espresso: Oly:Cremina,Maxi. MCAL... Grinder: Majors, Dienes Vac Pot: Hellem10 Drip: CCD, and more Roaster: 1kg. DreamRoast
Posted Fri Mar 30, 2012, 7:51am Subject: Re: Electrical Engineering Question about Behmor Heaters
onthemoors Said:
Regarding more control being safer, as offered by the resident genius, maybe he can explain how professional roasters with computer controls and other means of control often have bean ignitions.
I had thought most of those were generally exhaust flue related from oils/gases/chaff buildup, and exhaust motor issues? Unless someone just walked away and allowed the roast to go to third crack.
farmroast Senior Member Joined: 13 Jul 2006 Posts: 1,417 Location: Amherst MA. Expertise: I like coffee
Espresso: Oly:Cremina,Maxi. MCAL... Grinder: Majors, Dienes Vac Pot: Hellem10 Drip: CCD, and more Roaster: 1kg. DreamRoast
Posted Fri Mar 30, 2012, 7:53am Subject: Re: Electrical Engineering Question about Behmor Heaters
Any thoughts on why the chaff and escapees are singeing/burning on a Behmor? Is it because of the direct IR heating? Combined with the debris falling too close and in too direct a line with the IR? If the floor was a bit lower and maybe combined with some sort of a low shield to limit direct IR exposure to the debris field, might that help? My roaster expels 99+% of the chaff, the little that may remain doesn't even get that dark in color and never seen any singeing even though the air ET is rather similar. but my heating isn't IR exposure based.
Snaxx Senior Member Joined: 11 Dec 2008 Posts: 115 Location: Northeast Michigan, LP Expertise: I love coffee
Grinder: KitchenAid A9 Drip: Technivorm Moccamaster Roaster: I Roast2
Posted Fri Mar 30, 2012, 8:39pm Subject: Re: Electrical Engineering Question about Behmor Heaters
Any thoughts on why the chaff and escapees are singeing/burning on a Behmor?
My only experience with viewing the complete roast process in a Behmor is from a Youtube video that, I think someone from SM did to demonstrate it. I think your thoughts are within the area of reason as to why there are fire incidents occurring.
Comparing this with a fluid bed roaster such as my I-Roast; air, which is slightly compressed by the radial blade fan assembly, passes over a set of nichrome coil elements into the roast chamber. The airflow pushes the beans up through the center riser tube and then over the edge. This constant bean circulation with pressurized airflow never allows any beans to stall in circulation as long as pressurized air can exit the roast chamber out through the top. If the screens at the top become plugged and restricted from burned off coffee oils, or if the amount of chaff the beans release is excessive and plugs the chaff collector, then there is a potential for overheating the roaster and the beans, leading to a possible fire. There is a sensor which detects if the roaster is overheating, and if that occurs, the fan and the heater elements both shut off. This is really a poor design since the shutoff usually occurred for me, when the beans were just about into 2C. With the fan stopped, the beans are not circulating as they should, and also with the fan stopped, there is no way to cool the beans in the machine. You then need to get the beans out of the roaster and into a cooling basket or colander as soon as possible.
Like with your roaster, the I-roast pushes all the chaff up into the collector at the top, keeping it away from any direct prolonged heat, mostly eliminating any chance of a chaff induced fire.
With the Behmor; as you said, the direct IR quartz heat tubes seem to be one reason why escaping beans and falling chaff ignite during a roast. If they are just sitting there exposed to the direct heat, they're just taking up more and more heat on one side or area of the bean until the roast finishes, while the rest of the beans in the drum are still circulating and exposing 100% of the bean surface to the heat radiated from the IR tubes as the drum turns.
I think it was Germantownrob that recently mentioned the Behmor chaff collector had been redesigned to reduce this possibility of fire from escaping beans and falling chaff, so maybe yours hasn't been upgraded yet.
Posted Sat Mar 31, 2012, 10:35am Subject: Re: Electrical Engineering Question about Behmor Heaters
onthemoors Said:
Fires are a direct result of people either leaving the roaster unattended or not paying attention. This occurs in all equipment and a Behmore is no exception. If one were to ask all those who've had fires, if they were honest, they'd admit they were at fault except in cases of the laws of physics being defied.
Regarding more control being safer, as offered by the resident genius, maybe he can explain how professional roasters with computer controls and other means of control often have bean ignitions.
Occam's razor, simplest answer is the correct one, people are the cause. If people are provided twenty buttons, ten dials or just one such as cool they are still the final control.
Not a chance, man. Every one of my roasts is documented and observed. I have NEVER left a roast unattended. Not once. That's how I know exactly where and when and why any sparkups or small fires have happened.
The laws of physics are exactly at work here - roasting coffee takes temperatures into the combustion zone of light cellulose materials (like chaff). Since I can now keep the temperature from running away with an underload, I don't have to sit and watch a batch force its way through 1C and charge onto 450 deg before I want it to.
Apparently, you've already concluded that professional roasters with computer controls and other means of control have had bean ignitions because
onthemoors Said:
Fires are a direct result of people either leaving the roaster unattended or not paying attention. This occurs in all equipment and a Behmore is no exception. If one were to ask all those who've had fires, if they were honest, they'd admit they were at fault except in cases of the laws of physics being defied....
If one takes the time to read what I'm asking for, I'm actually asking for less buttons. P2, P3, P4 and P5 can all be created with a simple cutout switch.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Sat Mar 31, 2012, 11:27am Subject: Re: Electrical Engineering Question about Behmor Heaters
farmroast Said:
Any thoughts on why the chaff and escapees are singeing/burning on a Behmor? Is it because of the direct IR heating? Combined with the debris falling too close and in too direct a line with the IR? If the floor was a bit lower and maybe combined with some sort of a low shield to limit direct IR exposure to the debris field, might that help? My roaster expels 99+% of the chaff, the little that may remain doesn't even get that dark in color and never seen any singeing even though the air ET is rather similar. but my heating isn't IR exposure based.
The singeing escapees makes sense - they have one side exposed to the elements so that side gets twice the heating.
The only time I've had chaff by itself ignite was when the cool cycle stirred up excessive chaff that came into contact with the element.
In the cases where I've had bean singeing/smoking/burning, that's exactly the issue. I had a batch of Ethiopia Sidamo with about 7 escapees and three partial esacapees. The partials stuck in the drum mesh before they made it out but just when the beans were beginning to expand. 3 of the escapees fell out and rolled in front of the forward vane of the chaff tray, right under the element and direct LOS of the lower element.
The partials in the drum were charred on the tips but underroasted on the part inside the drum. I tried to salvage that batch by getting the tray out.
"hi chaff" and "low chaff" aren't exactly predictable. I've had DP beans with remarkably low chaff, and I've had wet-process beans with incredible amounts of chaff. It isn't region specific - the only way to know how much chaff a bean will produce is to try and roast them. YMMV, maybe there are some home roasters that have a chaff indicator.
Because my BMHG is forced air, the chaff is expelled out the chimney. I have taken batches well toward vienna with little more than smoke and visible oil on the bean surface (BT about 475 deg F), with no fire.
Don't get me wrong, I love the Behmor (now Romheb), and it was my intro to home roasting.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
rarebear Senior Member Joined: 13 Dec 2009 Posts: 212 Location: Rex. Georgia USA Expertise: I love coffee
Espresso: Fiorenzata Bricoletta Grinder: Mazzer Mini Vac Pot: Yama 8C Roaster: Hot Top B2
Posted Sun Apr 1, 2012, 9:27pm Subject: Re: Electrical Engineering Question about Behmor Heaters
farmroast Said:
I had thought most of those were generally exhaust flue related from oils/gases/chaff buildup, and exhaust motor issues? Unless someone just walked away and allowed the roast to go to third crack.
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