Thanks for sharing this. We are surprised to hear of a chaff fire in a Kaffelogic, and we do not expect the build up of discolouration to cause this. We would appreciate if you would give us a little more details, particularly the variety of beans, profile, and roast level. Did the fire start in the chamber, or in the chaff collector? And how much chaff was there in the collector at the time? We really would like to understand this better so we can improve the instructions in the manual.
Regards
Chris
There was only 1-2 cm of visible chaff in the collector (which is where the fire began) as was only on the 3rd roast after emptying. The beans were not affected, besides not completing the roast cycle so were thrown out.
This is basically how its been running for 3 years, so the scenario hasn't changed. In fact, I've actually roasted before with only 1-2 cm of gap in the chaff collector before (the lower chaff getting very dark, but not glowing).
On a side note, we did hit 40°+ on the Monday, so not sure if that affected anything... The Nano didn't feel any hotter than normal.
Thanks for the extra details. Would you say the chaff began to burn due to glowing chaff falling into the chaff collector, or due to chaff sitting in the chaff collector gradually heating up to the point it began to glow?
I would say the latter (sitting in collector against the oily mesh/metal tube). I think I've only ever seen lightly roasted chaff fall in, it just gets darker in the collector from the heat of the metal tube.
After our initial set of PledgeMe funded roasters we switched to a black anodised aluminium chimney. We have not had any reports of this type of incident with them. Although the black inside of these chimneys will absorb heat better than the shiny aluminium ones, the black exterior will also radiate heat better. The result will be overall cooler.
With a shiny aluminium tube, once the inside is blackened it will absorb heat well, but so long as the outside remains shiny it will not radiate it so well. The result may be higher surface temperature, potentially making it prone to this problem.
I think that would also have been combined with the very hot ambient air conditions on the day you had the issue. I would say keep a closer eye on things if temperatures exceed 35 deg C.
As you say, keeping the chimney clean is easy and desirable. Also this is a good reminder that the Kaffelogic Nano 7 should not be left completely unattended when roasting, so that there is someone in the vicinity to notice if an event like this takes place.
FWIW, my roaster is almost new (purchased mid-December 2020) and I had a chaff fire a week or so ago. The bean (Rwanda Nyungwe) is a chaff monster, however I was a little surprised by the fire (100g dose, perfectly empty chaff collector before the roast, 1500-2000 REST 3.4 profile). I just switched the roaster off, removed the chaff collector to a safe place and dumped the beans. I'm actually drinking them at the moment (a bit under done but perfectly ok). No harm done, but definitely worth staying near the roaster throughout the process.
Thanks for your report. It's not something we have picked up in testing, so good to have these reports coming in. We are quite concerned and surprised to hear of chaff fires. We are working on a redesign of the chaff collector which will isolate the chaff from the chimney and the intention is that it will eliminate this potential for fire.
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