There is a thread that talks about preheat and there are a lot of roasters on this forum that delay charging the Bullet by 10 to 15 minutes after getting the prompt to add beans for the first roast of the day.
Anyone know if there is a scientific reason for this? It would seem that once the drum is at a consistent temp, you should be good to go. Are there other components that require the additional time of activity, or time in proximity to the increased temp drum?
I believe that this is all about thermal mass and how much heat is building up and being stored in the Bullet. And this is not isolated to the Bullet. At around 4 minutes and 43 seconds Thompson and Dave are talking about Drum roassters in general not holding enough heat before the first roast. Dave talks about the finish temp for the current roast is higher than the Pre Heat for the recipe or profile that he is roasting to.
@Barry_p, posted on the “Time to Pre Heat” thread:
“for a while now I have been preheating to 300 deg c. then resetting the preheat to the temp I want and letting the temp drop to it. This has helped my first roast to be more consistant with followng roasts”
So he is overheating with a separate pre heat cycle and then resetting and running his regular profile with preheat cycle of the real roast.
I did this and it took about 13 minutes to get up to 550F then another 10 minutes before getting the charge prompt. (so 23 minutes for the first pre-heat)
then when I started my recipe or overlay, the bullet did another pre-heat which actually was a cooling cycle to come down to 400F which is my programmed pre-heat for that roast profile. that took 7 or 8 minutes.
I think that the difference here is that the Bullet gets more heat to soak into the thermal mass of the machine.
@babs told me that he takes a different approach. In a group of back to back roasts, he has a separate recipe for his first roast with a higher pre-heat. then for his second recipe he has his pre-heat set lower.
In theory, you could run an empty Bullet with your recipe or playback and just hit the PRS button when prompted for charge and let it run through to the end.
I ran a test with 2 roasts of identical beans and the same weight (400g)
I started off by doing a preheat to 527F and when it prompted me to charge, I cycled the PRS button until the Bullet panel showed “Off”.
I then, immediatley started my recipe that has a preheat of 401F. and ran that batch to completion. During loocking of the beans, I started the back to back cycle and roasted the second batch of beans.
The roast profiles were identical. I don’t ercall ever seeing 2 sequential roasts so similar.