Dave emailed re. preheat temps last night and we get asked about this a lot. This is his question and my take on preheating:

Cold weather finally rolled in here in NJ and this will be my first winter roasting on a 2KG digital.

I’m a bit lacking on the gas pressure in my facility so I compensate with some higher PH temps. The past few days I’ve been roasting in cold weather with a 460 PH. The coffee cupped great and I haven’t noticed any scorching — honestly cupped a bit better than my typical ~430 PH.

I was curious about the highest possible PH temp suggested when roasting a full batch on this machine.

You have discovered that your very thick and double walled drum allows very much elevated preheat. The upper limit is only heat defect relative to the size, moisture content, and density of the seed you are working with. Batch size is a thing too.
460-465F drum temp (not bean temp) is about the limit for me. YMMV.

Steve