"Let me start to say I am just a beginner. I have completed 6 washes and this run was a 4th gen. sweet feed wash with rye added. 10 gallon wash, 10 lbs. SF, 2 lbs. rye, and 12 lbs. sugar. Steeped the SF and rye for 1 hour in 2 gallons hot backset, melted sugar, cooled wash to 85F and added to fermenter. Aerated for 15 minutes with drill blender and capped off. SG was 1.082. Wash bubbled for 3 weeks. let clear for 4th week. FG was .996. so ran it on Black Friday.
Pulled off 8 oz. fores at 178F. collected in 6 oz. jars. First jar was 170p, which smelled like fores.
jars 2 and 3 were 152 p, jars 4 thru 8 were 150 p. all these jars came off at 184F. Proof dropped off a couple % each jar till jar 20 which was 135p and I could smell the tails. Jar 20 was collected at 189F.
My pot still has been really consistent with temp and proof to within a couple of %. The previous runs have all been rather predictable with regards to the constant temp rise and dropping proof. This one has me puzzled as to why the temp held for so long and the proof is so much higher than previous runs. never shut down the run with tails at so low of a temp before, but I figured if I smell tails, I'm done. Does anyone have any ideas as to why this run came off so differently as the earlier ones? Thanks, B."

Sounds like you are learning to run your still better as time goes on. I am no expert and still learning myself. If you are using gas as I do getting the temp right makes alot of difference. Said you had a 10 gal. wash and looks like you converted about 11%. Good job.

I run a lot of SF's - that long plateau is fairly normal, even in 5th-6th+ washes as I always add toss in's and backset from previous runs... It's even better once you oak it. I see the same behavior on both the BH PSII (In pot mode) as well as a 6 plate unit. In the plate unit I cut the number of plates to preserve the flavor profile and still get a good reflux to compress the heads as well.

But scientifically speaking, BW... the amount of time is proportional to the etoh content of the washes when you started and the power setting u used. Those variables can be fed into a formula to forecast that time line, but what you will find is nature takes her sweet time with the distillation process. The thermal dynamics of the wash change as the distillation process takes place simply from etoh molecules exiting via the differing factions they exist in. As the etoh goes, she heats up... But no two washes are exactly the same either