Help Please: Diedrich IR5 2016 - ET verses BT

[Law104]

Good Day
I am roasting on a Diedrich IR5 2016 model, using propane gas.

I am trying to not let my ET fall below the BT post FC.
Note;
1) At charge my ET is always lower than my BT. (not sure if this indicates a probe issue)
2) I only use 50% fan at approx 140 C. According to Scott Rao my fan sucks way to much air through the trier, when using the lighter test.
3) About 1min after FC my ET and BT cross over. I.E my ET is now lower than the BT.
4) Generally my ROR's are declining without noticeable "flicks or crashes"
5) My TP's seem a bit low 75 C.

My question is how could I avoid my ET dropping below my BT, without adding pressure after FC.

Please request any information that you think necessary to help.

Thank you..................

 

[Musicphan]

Do you know anyone else with this model of roaster? I find it a bit unusual that pre-charge your BT temp is higher than your ET. Where are the thermocouple located? Regarding fan - you only have the fan on at 140? Do you make other adjustments - it appears you have other changes. I assume you are dropping this close to the start of 2nd crack - right? TP means nothing... don't worry about that value.

 

[Law104]

Do you know anyone else with this model of roaster? I find it a bit unusual that pre-charge your BT temp is higher than your ET. Where are the thermocouple located? Regarding fan - you only have the fan on at 140? Do you make other adjustments - it appears you have other changes. I assume you are dropping this close to the start of 2nd crack - right? TP means nothing... don't worry about that value.

Musicphan thank you,
With regards to the thermocouples;
The ET thermocouple is located at the drum exhaust elbow at the back of the roaster. The BT couple is located on the front face of the machine below the trier.
In ran the machine cold without any beans, and both the BT and ET read exactly the same temp. I then tested both the couplers in ice water and both read 1.5 C. My conclusion is that there is no problem there.
I don't know of anyone with a roaster (IR5) nearby, in fact I don't know anyone with the same roaster. I have been roasting for 3 years, chucked allot of beans and from time to time had reasonable (taste) success. I am always looking for a better result. I have largely been self taught. I have been consulting with Scott Rao. This has been a bit disappointing, only because each bean, roaster, climate etc etc is so different.
I have been roasting with many adjustments mainly on the pressure side. For the first 2 years I have had mostly underdevelopment issues, partly because I have been to focused on a smoothly declining ROR.
With regards the fan, I have three setting 0%(through the cooling bin), 50% and 100%(through the roasting drum). With no fan, I test with a lighter flame at the trier, and there is a very noticeable pull on the flame. At 50% the draw almost pulls the flame out and 100% you can't keep the flame burning.
I read that the ET should ALWAYS be higher than the BT. Is this correct ? (It seems to make sense). I study my profiles (Artisan) and to get the ET to possibly remain higher (especially after FC), I think one option may be to leave the fan off during the entire roast. But this may have consequences.
If you have some time, I would greatly appreciate feedback. If it is any easier or more convenient that I call let me know.

 

[sae]

Is this your first batch of the day? Can you run us through the roast as far as how you pre-heat the drum, what gas and air flow adjustments you are making and when?

 

[NorthSouth]

Just because your reported numbers agree from both thermocouples at low temperatures doesn't necessarily mean they are good.
If you can, test them with boiling water.

 

[Law104]

View attachment Rwanda Roast Profile.pdf

Is this your first batch of the day? Can you run us through the roast as far as how you pre-heat the drum, what gas and air flow adjustments you are making and when?

Sae Hi,
Following are basic / average settings which I have been using. Each roast (origin does vary from this). Note the attached roast (the Colombia on the start of this thread) is something new I tried. See attached roast profile for the roast stats below. Rwanda AVIV washed 4000g green bean mass.

Preheat;
Switch on 5Mbar until I reach 15 C above charge temp (average 235 C).
Let the machine idle at 235 C at 3Mbar for 20min.
Let temp drop to 5 C above charge temp for 5 minutes switching gas on and off (max pressure 23Mbar).
Let temp drop to 20C below charge temp, then switch on max pressure 23Mbar. 10C before charge I load the hopper and at charge temp I drop the beans into the roaster.

Typical roast
.................Mbar. Time..ET......BT......dET dBT.........Dru Ex.T Ex.Inlet Temp
CHARGE #1 P22 00:00 201.1 212.6 20.5 20.5 -1.0 201.1 37.8...289.5
.............#2 P20 04:58 191.0 149.8 6.7 13.7 -1.0 191.0 37.5....358.3
.............#3 P18 05:31 196.5 159.5 6.7 13.6 -1.0 196.5 37.5....359.9
.............#4 P14 05:51 199.5 165.2 7.6 21.2 -1.0 199.5 37.8....359.7
50% fan #5 F50.05:58 200.8 167.0 13.4 13.4 -1.0 200.8 37.8 359.2 (50% fan left on for the remainder of the roast)
.............#6 P11.06:28 202.8 175.2 6.3 13.2 -1.0 202.8 39.7....338.7
.............#7 P8..06:50 203.8 180.8 0.2 14.0 -1.0 203.8 41.2......329.4
FC START...........08:15 207.1 198.3 0.7 7.6 -1.0 207.1 45.1.......309.9
10%DTR #9 P5..09:23 210.3 208.8 -1.5 5.2 -1.0 210.3 46.8......305.2
12%DTR#10 P3..09:36 210.8 210.0 0.0 6.9 -1.0 210.8 47.0.......302.2 (cannot go lower than 3Mbar)
17%DTR#11 P1..10:05 210.3 212.8 -0.2 6.7 -1.0 210.3 47.5......292.8 (pilot flame)
DROP 33% DTR...12:13 200.4 221.6 -6.7 0.2 -1.0 200.4 47.8......220.1

Thank you.................View attachment Rwanda Roast Profile.pdf

 

[Law104]

Just because your reported numbers agree from both thermocouples at low temperatures doesn't necessarily mean they are good.
If you can, test them with boiling water.

Hi,
I took it for granted, I will do so and let you know..
Thank you........

 

[Law104]

NorthSouth,
I checked the thermocouples perfect at water boiling temp, levelled out at 99.6 C..
Thanks for post......

 

[Musicphan]

I think what your experiencing is the fact your air is cooling off starting at first crack (which is related to you dropping energy). Where your thermocouple is located it doesn't completely surprise me. Most secondary ET thermocouples seem to be reading within the drum - for example, mine is located 10" above the BT. I have never heard of a golden rule that ET shouldn't drop below BT, really - if you're happy with the coffee I wouldn't worry about it. I only pay attention to ET to simply know where my coffee is going... I don't really care what the value is.

 

[peterjschmidt]

Based on your lighter flame 'test', I'm curious about how your roaster controls airflow - where the air is being drawn from. Is there a damper that is out of adjustment? I'd have to check my Ambex next time I roast, but it seems odd that you'd have the much draw into the trier when the airflow is supposed to be 100% drum.

 

[Law104]

Based on your lighter flame 'test', I'm curious about how your roaster controls airflow - where the air is being drawn from. Is there a damper that is out of adjustment? I'd have to check my Ambex next time I roast, but it seems odd that you'd have the much draw into the trier when the airflow is supposed to be 100% drum.

Included is a diagram and note of the airflow.

 

[sae]

I see that you never raise your air flow above 50%. Do you get rid of all your chaff even with 50% fan speed. I've had roasts where the ET is lower than the BT but as long as BT is still rising then I don't worry about it too much, especially in your case where the ET is measured after the air has gone through the bean mass.

 

[Law104]

I see that you never raise your air flow above 50%. Do you get rid of all your chaff even with 50% fan speed. I've had roasts where the ET is lower than the BT but as long as BT is still rising then I don't worry about it too much, especially in your case where the ET is measured after the air has gone through the bean mass.

Thanks..........
I seldom use more than 50% fan, I think all my chaff is removed. How can I tell?. I am going to do a few test roasts with 50% and 100% fan while watching my ROR.
Regards.........

 

[sae]

Any updates?

 

[Law104]

Any updates?

I have done a few more roasts with fan at 100%, at 185C until drop and some with 100% fan just after FC for a period of 30 seconds. I cannot see anything obviously different apart from a sharper drop in bean temp towards the end of the roast. I cannot see any difference with regards to chaff. I don't see any chaff at 50% or 100% fan. Is there a way of telling if all the chaff has been removed?
Thank you