You should reach the turn around point at 1 minute and 30 seconds. 4 minutes is far too long and you risk over-drying the batch. I would also recommend a much lower bottom out temperature- somewhere in the neighborhood of 180F-220F to avoid tipping. I roast on an IR-7 and a charge temperature of 370 works perfect for a single pound but, obviously, it's going to be vastly different for your machine. Best of luck!
Thanks for your reply. Another thought is that my bean probe potentially might not be reading correctly due to the small amount of beans with 1 lb. might drop faster when fully submerged with say 4-5 lbs.
A charger temp. of 330F with 1 lb. will not get me to 220F in 1.5 min. at all. Should I lower my charger temp. in order to reach 220F approx. in 1.5 min?
I think you might have hit the nail on the head with the probe placement issue. From the temperatures you cited, it sounds more like it's measuring environmental temperature rather than bean mass temperature. I would give customer service at Diedrich a call. It should be accurate with a single pound. I know that mine is and it's a much larger model.
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