Bean with agressive chaff killing my IR? (BT over IR to stop overheating)?

Hi everyone.

I have this Colombia big bean naturaly processed. when I roast it I can see very big chaff pealing off (like really big pieces, never saw that big). the chaff is so much in volume and size after say 3 roasts my IR sensor goes completelly off and goes way down under BT during roasts. (i checked whether my IBTS fan works ok and it does) By now i know that means the IR lens is dirty. So I take off the faceplate and clean the IR lens (really dirty) and for a few roasts it is ok but soon it is back off.

All the coffee (also other beans) that I roasted when the IR is off tastes very bad, very roasty.

What happens is I cant get end temperature low enough (i see the IR is off so I go by BT. first crack happens around 190°C BT so I assume the BT reads ok but even with short development time like 1minute for filter roast, i cannot get lower end temp than around 205°C). I guess that is because as the IR lense is dirty, the bullet is preheating. I have not yet succeeded to get a decent roast out of this colombia.

I will stop roasting this Colombia bean so as to confirm my theory that this bean with its extraordinary chaff messes with the IR lense.

My questions:

  1. Is it really so that when the IR lense is dirty, you are unable to roast due to overheating?

2 if so, would the solution be to switch to classic BT as a main probe so as to get around the overheating issue and so be able to roast this particular bean?

I will try to find out myself but would love to hear from you any input that could help me.

thanks a lot

EDIT: Ok I have checked the IR lens after 1 roasting session (consisting of 4 x 800g and three small sample batches, all other beans than that killer columbia) and it is dirty. (it was perfectly cleaned before this one session) and this is what it looks like:

you can see the lens is dirty, probably not too much, but this is only after one short roasting session. So when the manual says you probably never have to even clean it, if you dont roast too dark (I dont), I guess this is pretty dirty considering?

Can there be something wrong?

Thanks a lot

That does seem unusual— never happened to me.
When I clean the lens, it always looks the same before and after. Yours is obviously dirty, I’ve not seen that before.

I would consider that very unusual. I’ve never seen the IR sensor with chaff across the lens. It just ought not be there. I can think of 2 possibilities-

  • something is blocking the free flow of air from the air inlet in the base of the control panel housing (the slots kinda point toward the bean chute)

  • there is air moving around the roaster that is fast enough to catch the chaff dribbling from the base of the door and blow that chaff up toward the air inlets. The IR fan is moving at something close to 16,000 rpm so it will make dust of the chaff when it hits the blades.

If you’re getting enough contamination on the IR lens to reverse the position of B-Temp & IBTS, this also means the drum is preheating substantially hotter than you think it is.


Your IBTS fan is not mounted the wrong way is it? Does your IR ambient every get too high?
You could try FW 606 which should prevent contamination during preheating.

Hi all and thanks for the replies.

my IBTS is not wrongly mounted, I have taken off the CP and checked (aillio support suggested that).

the IR ambient was 49,5 when I checked the info panel during a roast and took a screenshot. I dont know what it is or whether it is high, anyway, I am using C degrees

Could you please explain what is FW 606? Some kind of cleaning solution?

there is no blockage of the air inlet towards IBTS and also there is no fast air movement around the bullet. Although I roast on a balcony, this balcony is completely enclosed

I know I was roasting for a quiete a few roast sessions with a very dirty chaff filter (I know that is a bad mistake, but when I read the manual saying probably it wont need cleaning if not roasting dark and much, which I dont, I automatically disregarded the need of checking it.) But now the filter and the impelled are perfectly clean for a long time back, so I dont understand this. Maybe I have permanently damaged the IBTS somehow?

Appreciate any thoughts on my issue, thank you all very much

If your chaff filter is very dirty there will be almost no airflow, and some of the air will go back across the IBTS and enter the control board. This will eventually damage both IBTS, LED board and Control board, so please make sure to clean this often.
I would try again with a very clean filter. Also make sure the whole IBTS is seated in the silicone holder, and that there is no gaps.

Jacob, I understand that and my recent roasts are with completely cleaned filter and everything and the problem is still present. And thats what I did with the IBTS when took of the CP, made sure there was no gap around the holder. So maybe I did some damage to the IBTS or CB? Or that would present itself with an error code?

Thanks a lot

There are no errors unless something overheats or stops spinning.
Don’t know what else it could be.
Next time you clean the IBTS please take some photos from inside the bullet, showing the IBTS and seal.
I looked at your logs, everything seems OK.
How do you vent it?

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I roast on a balcony that is 7metres x 1meter big. It is completely closed, except for i open a window on one end and I roast at the other end. So i use no ducts or extra ventilation.