Is the experience thus far that boil off is very very low? Like .50 to .75 per hour?
Yesterday I brought 7.85 gallons to 164 in my Bayou Classic 1044 (it's the valve version of the 10 gallon pot).
I pumped that to my MLT, which upon doing so, I lost about 4 degrees of heat so I stopped the pump, turned on the kettle again and heated to about 170 quickly to offset heat loss. I mashed in, pumped back to the kettle (did no sparge) and as soon as I had 2 gallons in the pot, I turned the burner on to 2700. I got my boil volume which ended up being 6 gallons; I was aiming for 5.96 so this is good. I had a "duh" moment with my new pump and proceeded to dump .25 gallons of wort on my floor because sticky wort on my floor is the best, and turned the burner up to 3500.
From my 1 gallon and my failed 5 gallon batch (last Friday) I knew I had to literally plant myself next to the burner, and I did. Some short time passed and suddenly the wort was at the top waiting to boil over. Quickly turned the heat down to 800, sprayed my wort so it would calm down, and I came back up to about 2000 (I believe these are the increments). When I was comfortable, I went to 2400 then 2700 and I stuck at 2700 with a very nice rolling boil.
I boiled with what I call a consistent rolling boil for 60 minutes and lost about .50 - .75 gallons to boil off. I figure .25 on the floor, .25 left behind in the pump tubes and trub, .75 boil off = 4.75 in my fermenter.
Does that boil off sound about right? Unfortunately, I didn't time my boil times, I was busy with the new pump and such but I turned the burner on at 1:28 pm and I was chilling my wort just after 5.
I also love how easily this thing cleans up. I have dripped wort down the sides and worried a lot. It seems to clean right up. I do have a ring on the bottom of my pot as well. I will snap a pic of it in a bit.
Last night, during my first time brew with the IC3500, I estimate boiling off at least a gallon during the 75' boil. I'd say 25% less than I'm used to on the stove. I posted a more detailed report in the other IC3500 thread.
You're fortunate, your 10 gallon kettle has a lot more net headspace than my 8 gallon MoreBeer one. What were they thinking designing such a weird under-sized pot? Extract/partial mash perhaps? At least it will last a life time and then some. The triple-ply bottom helps to prevent scorching, and redistribute the heat, although I do give it a good stir every now and then. I guess it's habit from the extract days.
"Sticky wort on my floor is the best..." Very funny! No good brewday is complete without. Not sure if this method is much better. In one of my first AG brews I managed to leave the kettle valve open while dumping in my first runnings. Luckily I had my HLT still underneath filled with 4 gallons of sparge water... I discovered the error fast from the sound it made, but by the time I could close the valve I had diluted at least a gallon of 1.090 wort into sparge. Still made the OG, and the beer came out fine.