Help Please: Temperature probe readings seems wrong

[Ruup]

Good day to the all the members.

I have a query regarding the temperature readings of my 5KG Has Garanti roaster.

I know there are plenty of variables within the coffee roasting process, however I am reaching first crack at 155 degree C on my roaster. Can this be correct? It seems like it is more common to reach first crack closer to 190 degree C and upwards.


The thermo probe seems like it has been factory fitted and is fitted to the right of the sight glass.



Could this be a faulty thermo probe?


The guy I bought it from also reached first crack at that temp however if first crack is reached at 155 degree Celcius, does that mean the reading is off and the actual temp is higher towards the 190 degree C mark? In other words, theoretically, can a bean only achieve first crack towards the 185/190 degree mark or is it possible to reach first crack at 155 because that seems very low.


Your advise and suggestions will be gladly appreciated.


Looking forward to hear from you.

 

[Musicphan]

Something is off if your hitting FC at 155C... usually, it's more like 195-200C. A couple of things to check - first I would do is check within your monitoring software that you have the thermocouple Type select correctly. It almost sounds like your thermcouple Type is selected incorrectly. Does your temperature read 'normal' close to room temp when the roaster is cold, then become more 'inacccurate' the higher the temp? (usually a sign). The second thing is placement - is the prob actually in the right location to hit the bean mass? Is it deep enough into your roaster to hit the bean mass? (you may have to feel inside the roaster when cold.. sometimes impossible).

 

[Ruup]

Thanks for the reply guys.

When switching the machine on, the room temp reading inside the cold drum seems correct at around 17.5 degree in my workshop.

The machine is not connected to roasting software at the moment, that is the reading I get on the roaster itself. I can feel the probe inside the drum and it sits fine.

What I find interesting is that in these videos on youtube, they are using the same roaster and it looks like they are also getting the same temp readings on their Has Garanti.

Tried to add the links but can't yet as I am new on the forum:

First clip - they charge at around 140 degree celsius
Second clip - here they drop what seems like close to 150 degree celsius which is even lower

I am trying to find out if the reading is off and if the actual correct temp is higher? In other words, theoretically, can a bean only achieve first crack towards the 185/190 degree mark or is it possible to reach first crack at 155 because that is what is happening with my roaster and with the one in the video.

Any thoughts? I have also contacted the guys who made the video to hear what they are saying.

 

[Musicphan]

I looked at the model online just to get an idea of the roaster (they are somewhat unheard of in the US)... it looks like the thermocouple is positioned correctly. And I assume your green charge weight is close to 3K or greater - sometimes running small loads the bean mass won't be high enough in the roaster to get accurate readings.

I would look within your manual or see if there is any setting for Thermocouple Type configuration.... when I first received my US Roaster Corp roaster I had them mistyped and I would get 'normal' readings at ambient/close to ambient temp.. but as it rose in temp it became greater and greater off from what it should have been.

Your drop temp will impact your 'speed' of roast - 140-150 seems low.. I'm generally closer to 200. And regards to FC... in my experience green cracks around similar temp's... almost every bean I roast hits FC around 195. I do have a super fresh Guat which is probably hits FC at 185c but that's rare.

 

[Musicphan]

This may help as a visual comparison of roast / degree..

 

[Ruup]

Thanks for your feedback Musicphan.

Will try to get my hands on a manual.

If I look at the visual comparison, what is showed in the picture at 201 degrees is what my beans look like when my thermo reading is at 160 degrees. However I also get consistent FC at 155.

 

[Ruup]

Here is the links to the video on youtube where they roast on the same roaster and the temp readings look similar to mine.

https://www.youtube.com/watch?v=RrQCAoW810s&t=4s in this video it looks like they are charging at around 140
https://www.youtube.com/watch?v=pkUxysSVuao here it looks like they drop close to 150

 

[Musicphan]

I'm perplexed... especially seeing the video, you can hear audible snaps so you know its at FC (or close).

 

[NorthSouth]

I don't believe the temperature readings you are seeing are correct, based upon your description.
I also disbelieve the temp readings on the second video (and therefore probably the first too).
So why are the videos somewhat matching your experience?
Perhaps some type of manufacturing error?

1. As Musicphan said, see if the roaster has some configuration for thermocouple type.
If the roaster's setting for thermocouple type doesn't match the actual type of the thermocouple, that would certainly cause incorrect temp readings.

2. Talk to Has Garanti support. Maybe they have a known problem.
Because the second video indicates a similar issue, perhaps there was a bad batch of thermocouples or incorrect type of thermocouples delivered to the manufacturer.

3. Thermocouples aren't the world's most reliable items.
It's possible that you have a faulty thermocouple.
Thermocouples aren't too expensive.
I would consider buying and installing (easier said than done) replacement thermocouple.

4. Provided the temp readouts are consistent, even if they are consistently wrong, you can continue to roast.
Your eyes, ears and nose will tell you when the beans are done.
You can learn what are "normal" numbers for this roaster.
Just bear in mind that it would be very misleading to assume these numbers would be of value when another roaster is in use.
Personally, I would hate to live with such a large discrepancy with reality.
While every roaster has slightly different temperature readings, they are normally within a reasonable margin of error.

 

[Ruup]

Thanks for taking the time to give your feedback and suggestions.

I agree that the temp readings I get is incorrect. It seems like to temp readings are off by anything between 50 and 60 degrees.

I will get in touch with Has Garanti support and will revert back here if I receive any info from them.

At least the readings are consistent, but yes would like to roast seeing correct readings.

 

[Musicphan]

4. Provided the temp readouts are consistent, even if they are consistently wrong, you can continue to roast.
Your eyes, ears and nose will tell you when the beans are done.
You can learn what are "normal" numbers for this roaster.
Just bear in mind that it would be very misleading to assume these numbers would be of value when another roaster is in use.
Personally, I would hate to live with such a large discrepancy with reality.
While every roaster has slightly different temperature readings, they are normally within a reasonable margin of error.

One note regarding this.. if you are using software such as Artisian to monitor your roasts - you can use an offset to 'correct' the temp reading. For example, my thermocouple location in my sample roaster is in a poor position resulting in an 'off' temperature. I adjusted the settings to bump up the temp in Artisian so at least between my to roasters I have somewhat relative milestones. It obviously doesn't fix the problem but can help.