FC temperature much higher after replacing IBTS fan

Roasting on the Bullet R1
1

I use the IBTS to roast. FC has always been just over 400 degrees F. The IBTS fan failed and after replacing it, FC is much higher. Any ideas?

2

If you only changed the fan then this is a little bit strange. You could try to check all alignment again (silicone housing, front plate etc) and carefully clean the sensor lens.

3

If you also cleaned the IBTS glass while you were changing the fan that could account for the difference. I just cleaned mine and the bean probe and FC temps increased by 5-7 degrees Celsius.

4

I did clean the IBTS glass as part of the fan replacement and your observation of an increase of 5-7 C is about what I am seeing. What is the difference between your IBTS temp and your bean probe temp at FC? Thanks

5

Just some random thoughts about the temp differences you’re seeing…

Temp difference between IBTS and the probe at 1Cs is about 30F°/16C° on my R1 Bullet. That varies as a function of sensor calibration and batch size (I use 550 gm batches). Not your issue, but when a sensor is replaced in the field there is (probably) no attendant calibration to standardize the readings… it’s whatever the calibration was for the original sensor. Also that difference varies with batch size: the larger the batch the smaller the difference.

Another variable is air flow past the IBTS. A change in flow rate between your old fan and the replacement will affect the operating temp of the IBTS. So too will room ambient temp though that can vary from significant with no AC to trivial if you roast in a temp controlled environment. The IBTS fan is pulling air from the space in front of the roaster front plate which is a little warmer than room ambient.

You’ll likely see some change in the IBTS vs. probe temp difference as roast history increases over the next few years. That can be attributed to aging of the sensor circuitry. And as you mention, maintenance to remove contaminants on the IBTS lens will make a significant difference in IBTS readings.

Bruce

6

Thanks for your insight. I roast between 500 and 550g/batch and will check the delta between the sensors at FC the next time I roast and report back.

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7

IBTS reads about 16 C higher than bean probe @ FC and stayed the same until end of roast 2:45 later.
I also roast ~ 565g batches.

8

I had the same experience. Thank goodness for the roast analyzer and the bean temperature. I am now charging 15 degrees Celsius higher. It’s not linear, either. On one of my regular beans, where I end the roast at 204 c, I am now ending at 211 c. So I see 15 degrees for the charge and 7 degrees at the end. The new temperature readings are now more consistent with what would be normal for the first crack. but that first roast had me scratching my head with a hearty WTF.