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Homeroasters - Home Roasting Coffee Community » ALL ABOUT ROASTERS » Fresh Roast 8 and NEW SR 500

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SR 500 temp drop
kwrcst	#1 Posted on 01/30/2019 11:09 PM
1/4 Pounder Posts: 75 Joined: November 26, 2018	So I have a thermocouple installed on my sr500. It reaches just below the metal ring on the cup. What I?ve consistantly seen happen is I get to first crack, around 415-420 and when they light off and start popping, my temp drops 10-20 degrees. I thought maybe it was something about that temp and it was cycling and that?s why but tonight I hit FC around 405 and I dropped to about 390. My problem with this is my FC stalls out at that temp drop. Once I get back to it, the rest start going again. I?m sure this effecting my overall flavor profile because I can?t roll through it. Like it?s baking some and not the others Anyone else seeing this happen? Could FC really cause a temp change in the chamber by that much? I know it?s not exact bean temp but I?m in the mass pretty good so I?d imagine it?s as accurate as I?mgojng to get.


renatoa	#2 Posted on 01/31/2019 1:58 AM
Administrator Posts: 2424 Joined: September 30, 2016	Crack is due to the humidity inside bean reaching the vaporization temperature and causing a small fracture with violent ejection of steam. Because steam is "only" 100 C, indeed it could be the reason of drop in such small roast chamber volume. It is less noticeable when happens in a 3-6 litres roast chambers, for pound-kg roasters.


kwrcst	#3 Posted on 01/31/2019 5:27 PM
1/4 Pounder Posts: 75 Joined: November 26, 2018	At least I?m not going crazy. I guess I need to roll into FC on high with the fan lower than 1/2 Thanks for the reassurance


8675309	#4 Posted on 01/31/2019 8:36 PM
1/4 Pounder Posts: 91 Joined: August 02, 2018	Nothing worse than a stall.. took me many a bean to get my SR500 to produce a consistent good drink. You may find this helpful... https://forum.homeroasters.org/forum/viewthread.php?thread_id=5773&pid=67693#post_67693 It's bad luck to be superstitious


renatoa	#5 Posted on 02/01/2019 1:52 AM
Administrator Posts: 2424 Joined: September 30, 2016	Imo, flicks and crashes are the fears of this hobby that was been invented by someone to provide usual suspects for not so good roasts. For hot air based roasters, the key is to pump as possible constant and slow raising heat into beans for the whole process. The inertia being the smallest of all roast methods, the worst treatment to beans is to erratically change power levels across the profile, the power change of heater will be immediately sensed by beans. That's why using a PID control profile following, especially when PID not tuned, is the least recommended method of power control. Could be acceptable if coefficient values are chosen to ensure a big dampening of the output fluctuations. Much better is to use several fixed power levels, manually changed based on experience. I had stunning roasts with only three power changes across the whole "profile", and no airflow change. (not fluid bed machine) Again, take all the above as just my opinion... other machines behaviour could vary. As Jim Schulman wrote " ...the heat inputs required moment by moment to achieve this ET curve is based on the roaster's thermal characteristics, and is different for every roaster design" Edited by renatoa on 02/01/2019 6:15 AM


kwrcst	#6 Posted on 02/01/2019 8:05 AM
1/4 Pounder Posts: 75 Joined: November 26, 2018	well said thank you

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