Sudden changes in roast profiles. (Roaster TOO HOT!) Please help
Roasting noob here looking for a little help
I have been roasting on a used diedrich IR-3 that I bought a few months ago. It's an 06' model.
I started roasting with a 60 lb bag of Costa rica Bajo de Canet Tarrazu. I have been using similar profiles that I learned in an apprenticeship on an IR-12.
for the first few batches everything went as planned and we were making some pretty decent tasting coffee
Then after about 12 batches, using the exact same costa rican coffee, the exact same green coffee weight, and the same adjustments involving energy and airflow, I'm getting much higher temps throughout the roast. I'm suddenly jumping an extra 5 to ten degrees every 30 seconds and I'm flying through first crack and hitting second shorlty after (20 to 30 seconds)
I tried to adjust accordingly by using more weight, lowering the temp at drop time, letting airflow through the drum sooner, and turning down the energy a bit more for first crack. It seems that even if i start the roast with the gas a little over half (as opposed to full in my first 12 batches), I'm climbing way too fast. And by the time I turn the energy down at first crack it starts to fizzle out and temp stops climbing
-Is my temp probe or my digital display of temp not functioning properly?
-Do I have an airflow problem?
Any tips on how to troubleshoot this problem would be much appreciated
Why is everything suddenly TOO HOT?
Replies to This Discussion
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Permalink Reply by nick placakis on
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A few questions. What temp. is the environment of the storage of the green coffee? Have the temps. had any extreme changes in the facility? How old is the coffee? Is the temperature of the roasting facility stabalized or is roasting taking place during varying enviromental temps. Ex. is the raosting facility 60 degrees one day then 80 degrees on another day?
Please provide a little more detail on the environment where roasting is taking place to rule out a few possibilities.
Nick
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Permalink Reply by Owen Garcia on
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Thanks nick
Yes the roasting environment did change. This was the first thing I suspected. When I started it was september and pretty warm. We were just roasting outside. I noticed a difference when the the outside temp got cooler in november and december.I ended up moving it into a friends garage. I got a venting system together and it leads out a window with everything fairly closed off. The garage is old and definately drafty. But with the door closed and my new propane heater working the space hits up pretty quickly. I can get it to 65 or 70 degrees and I wait until the metal on the outside of the roaster is warm.
So my roaster is basically being stored in an uncontrolled pretty cold environment (Maine) and I'm trying to heat up the roaster and the surrounding environment with a propane heater.
As far as the beans go I have been storing them in plastic bins in my Apt. where temps stay pretty much the same. Although the air in here gets a little hot. We don't have any control over our heat
Is my roaster spending too much time in the cold?
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Permalink Reply by Keith Eckert on
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Could be many things, but a couple thoughts:
-have you cleaned the impeller fan (as well as your normal thorough clean-out, of course).
-the older beans become, and especially in cold/dry air, they can quickly lose moisture content. Low moisture in general = faster roasting.
Diedrich roasters use a heat exchange system to warm the convection air that travels through the drum. In all the IR-3's I have seen, they only have one temp probe (argh!) which is bean temp. You just have to believe/hope that the air traveling through the drum is in the 400-420 range as designed.
OK, so here is a theory: if you warm a cold diedrich you can potentially over heat the drum before the heat exchange system has reached equilibrium. The single temp probe isn't accurate until it is surrounded by beans, so in your pre-heating routine the under-heated exchange system is pumping cool air into the drum causing you to think the roaster is colder than it actually is. So when you get to temp, you drop you beans at what you think is your drop temp, but the actual drum temp is 50-100 degrees hotter. In a cold winter with dry air (the specific heat of humid air is much higher than dry) and a really cold roaster, the first roast could really be challenging to profile from.
If you do 3-4 roasts to allow the roaster to gain its thermal equilibrium, do you notice the problem persists? From what you said, it seems like you only roast 1 or 2 small batches at the most...so I would suggest allowing more time for the machine to pre-heat before roasting.
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Permalink Reply by Dustin DeMers on
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Maybe a minute by minute play of your typical roast, then your changed roast. Time and temp each minute, letting us know when the drying phase is over, and then when first hits. Also how does the coffee taste on these run away roasts?
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My first inclination is the coffee is losing humidity due to the drastic temp. changes. Remember that especially when the temp. of the storage area gets hotter, the greens will begin losing humidity which is robbing the coffee of potential flavor. This is why when roasters take possession of large quantities of green, they will sample the bean humidity level to ensure it hasn't lost humidity from its storage and transportation prior to reaching its destination.
Based on what you have disclosed so far, my first guess is the loss of humidity is causing the roasts to run quicker and hotter and getting to first crack so quickly. Proper storage is imperative not only gets optimal flavor but also to be able to replicate a profile you have identified as optimal for that coffee. It doesnt mean you can't produce a decent cup, it just means you may not be able to get the best out of that coffee. I will return to this I just have to run quickly due to crying children... sorry. be back later. LOL.
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Thanks guys
Yea I think i'll take it apart tomorrow morning and give it a deeper cleaning. Especially that impeller fan.
Also gunna give it a longer and slower charge before I bring it back down and drop the beans.
Will report back
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Permalink Reply by Brady on
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Hi Owen.
Sounds like a lot of people are also talking about the change in moisture in your greens. Is this something you are tracking? If not, you probably should. I was looking around just now for a piece I saw on this recently but couldn't find it. I think the bottom line involved tracking changes in bean weight density using an accurate scale and a tall graduated cylinder. This approach doesn't give you absolute moisture numbers (which would require a meter), but it will let you see changes so that you can change your approach accordingly. Hope that helps.
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Permalink Reply by Jason Shipley on
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Your changes in profile seem too drastic to be attributed to moisture loss. I think I would look at your gas valves and pressure regulator.
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Permalink Reply by Craig on
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During your cleaning be sure to remove the box that the green bean hopper slips into, which is bolted to the front plate. You may find build up in that area. Also check the air flapper to make sure the flapper is in it's correct position when in through drum, 50/50, and cooling positions.
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