IBTS... To clean or not to clean? That is the question

For Bullets with the new IBTS, is there an official recommendation as to cleaning the inside face (IBTS) of the Bullet. The IBTS is said to be self cleaning. On older machines, there is a recommendation to clean the inside every 10kg roasts. I assume that since the IBTS is self cleaning that the every 10kg cleaning recommendation no longer applies.

Is there an official recommendation. It is not clear to me in the updated manual 2.8 .

My new IBTS is still receiving coffee oil build-up and I need to clean it every 25 lbs (10-11 kg). I’m curious to see if anyone else’s new IBTS is seeing coffee oil build up?

If you see that your FC temperatures are suddenly different then you should inspect the sensor and clean it with a cotton bud and a drop of alcohol. We are investigating why some IBTSs still have a little residue on them. One of the theories is that dust while filling the hopper travels down the side and is being sucked into the micro fan and then onto the sensor.


I also struggle with my IBTS. For the first 100kg it worked fine, but since 2 months or so I need to clean it at least every 10kg since IBTS temp drop by about 2°C.
Any help would be well appreciated.

I’ve seen the same thing. My current favorite suspicion is that we may be seeing some aging in the IR sensor as well as some accumulation of roasting ‘stuff’. ‘Stuff’ means I have never seen anything on the cotton swab after cleaning, yet cleaning makes a difference in IR levels during the roast. ‘Aging’ means that no amount of cleaning has restored the original values I saw before I realized there was a need for cleaning.

Recently I noticed that batch size changes the difference between BT & IBTS levels: a larger batch brings IBTS closer to BT values, especially at the end of the roast. Unfortunately I can’t tell if IBTS is lower or if BT is higher. This isn’t a change in IBTS behavior- it’s just that I always roast 550 gm batches till the day I tried one 800 gm batch and one 1 kg batch. The difference between IBTS vs BT was noticeably smaller. And again, there’s no clear way to tell if one or both of the sensors is different.



It makes sense that BT is higher for larger batch sizes, where the thermocouple is more fully immersed in the bean mass. I’ve been concerned about the other end of this issue: is BT temperature unreliably low for small batch sizes like 325g?

I wonder about that as well. I started using the Bullet with 300 gm loads but finally thought “why am I doing a small batch like this? limited loads was a HotTop thing”. I can’t answer your question but as I think back I seem to recall having trouble correlating 300 gm vs. 550 gm roast profiles. I’ll see what a little digging turns up but I didn’t keep very good notes 2 years ago.


I roasted about 18 batches, including seasoning. Then I had to remove the motor to fasten the tiny wheel back onto the motor drive shaft (both of the tiny recessed screws were completely loose). While I was at it I looked at the IBTS and it looked like it had a really bad cataract, it was milky white. Kind of explains why I’ve been finishing FC quite a few degrees earlier than I expected. Also the roasts have been going pretty quick probably because I’ve been driving the temp higher than I thought I was. Guess I’ll be pulling off the front panel regularly from now on.

Try this…

Pay attention to the difference between IBTS and BT at about IBTS 320 deg F. With my 550 gm batch size, when I see that difference reduce to less that 40 F deg (a difference of say about 37 F deg) I know it’s near time to clean the front panel & IBTS. For smaller batch sizes the difference will be larger and conversely for larger batches the difference will be smaller (making it a little harder to judge). I have found that difference to be consistent from roast-to-roast and a reliable indicator for sensor maintenance.

If you’re seeing whitish deposits on the lens of the ir sensor it may suggest you’re getting smoke near the base of the pedestal for the Control Panel… that base has openings that are the air inlet for the ir sensor cooling fan. You might want to pay attention to where smoke is drifting as you finish the roast e.g. when dropping the beans. There’s often smoke above the cooling tray right after the drop that can be picked up by the ir sensor cooling fan thru the inlets at the base. If you see that happening, a strategically placed fan may help steer it away. I’ve not seen smoke in that area during a roast… just when I start cooling.

I’ve cleaned the sensor many times and have never seen anything on the cotton swab. But the temp difference will be restored as IBTS data shifts. If you don’t see a shift in temp difference (in my case from T-difference =37 to T-difference greater than 40), then it may require more passes with the alcohol-wetted swab.


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