What does it mean when you see one of these warnings?
Thermal runaway
Press ▶ to cool
or
Thermal dip
Press ▶ to cool
This is an indication that the beans are not circulating properly and is known as ‘Bean lock’. Due to lack of circulation hot air has become trapped in the bottom of the roast chamber, causing anomalies at the temperature probe. Roasting cannot proceed in a controlled way, so the roaster has stopped and is waiting for your intervention.
In vary rare cases the hot air trapped in the bottom of the roast chamber has heated some beans to the point where they begin to smoulder. In such a case you will see billows of dense black smoke, or in exceptionally rare cases you will see glowing beans or flames. If this is the case, turn the roaster off at the wall and treat as a chaff fire. This is a very rare situation that most Kaffelogic users will never see.
In the normal case simply press ▶ to start cooling and wait for the cooling cycle to complete. In most cases the beans you were roasting will be ruined because the beans were not roasted evenly and the roast stopped early.
When the beans are cool and the roaster has stopped you need to make adjustments to your roasting practice so that the beans circulate adequately throughout the next roast cycle. This might be a smaller load or a higher fan speed: details are in the Bean lock article.
Is Bean Lock the only cause of these warnings?
No. There are other possible causes.
If an element burns out during a roast you will get a thermal dip warning shortly after the element stops working. Test for this with a subsequent empty roast test: see Roaster not heating. The roaster will show a ‘Heat too slow’ warning during the empty roast test and your element needs to be replaced.
If an element is malfunctioning (faulty thermal link, but element not burnt out) this can cause either thermal dip or thermal runaway warnings. This can be tested with a standard test roast:
recalibrate bean circulation,
use beans of average size and density such as most Colombian varieties,
roast a 120g batch, and
use the default profile (Kaffelogic Classic).
If thermal runaway or thermal dip errors occur during a standard test roast, the element is most likely faulty and needs to be replaced.
If you are in doubt about whether one of these faults might be present, contact customer support for assistance.
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