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Heating Element Failure -- help?
CharcoalRoaster
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Posted on 12/08/2020 8:34 AM
A lot of bad luck in the garage this weekend -- Glass RC fell to the floor and broke and I am out of coffee! (thought I'd spring for a 12oz bag to get me through the week and repairs = $26! this coffee better be GOLD). Anyway, grabbed some spare parts and rigged up my new build to hopefully just get a roast or two in before totally finishing it up and connecting it to Artisan and TC4. Here's what I ran into... thumbdown

Bigger blower for this new build runs at probably 15-20% with the 500g test load before it blows the beans out of the RC -- no biggie and good news honestly as I'm hoping to be able to get to 1-2kg loads when all is said and done.

Hooked up the heater and everything was going swimmingly until heat cut out and I had to pull things apart to figure out what was going on. Discovered my element somehow shorted out or something but I repaired it and reinstalled for another test run. Within 45-90 seconds I noticed temp dropping not rising again. Looked down and one of the connectors had come loose off the element terminal. I cut power, re-connected and switched element back on. Still nothing. Pulled everything apart again and the element (brand new btw) was completely oxidized and had another break in the coil.

I can either deduce this is from...

(1) Airflow being too low - due to running the vac blower at 15%ish
(2) Bad connection with that one terminal connector caused it to overheat and oxidize to the point of failure

Any help would be appreciated!
CharcoalRoaster attached the following image:
element_4.jpg
 
renatoa
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Posted on 12/08/2020 10:13 AM
A fan forced to run so low is no good... sensitive to load changes like pressure due to chaff clogging... => a lot of speed variations, thus unstable air temperature.

Back to pan roasting then... BBQ grill
Edited by renatoa on 12/08/2020 10:27 AM
 
allenb
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Posted on 12/10/2020 11:35 AM
Shoot us some photos of the point of failure
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
CharcoalRoaster
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Posted on 12/10/2020 2:54 PM

Quote

allenb wrote:

Shoot us some photos of the point of failure


Point of failure was along the middle of the coil nowhere near the terminal connectors. The first failure looked almost like an accidental contact point that shorted out and melted the coil in that point of contact. The second failure was in a completely different spot on the coil.
 
allenb
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Posted on 12/10/2020 4:49 PM
I've seen some elements that tended to move about if a particular area had less than minimum needed air passing by it and it would expand enough to cause the area to bow out and touch to ground or touch another coil. Maybe this is happening!
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
CharcoalRoaster
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Posted on 12/10/2020 6:40 PM

Quote

allenb wrote:

I've seen some elements that tended to move about if a particular area had less than minimum needed air passing by it and it would expand enough to cause the area to bow out and touch to ground or touch another coil. Maybe this is happening!


Interesting! I would have thought too much airflow would potentially move the coils but not distortion due to lack of airflow. Thanks Allen -- I received a new coil today I'm gonna fit up this weekend woohoo
 
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