Hey guys,
I know this question can’t be answered w/100% accuracy without more info, but here’s the situation . I got my Blichman Floor Burner in the mail today. Brewing a 5 gallon PM batch tomorrow, but don’t have time to do a test boil like I intended (couple busy days coming up, and I don’t want my crushed grains to sit out too long). I’ll be using the 8 gallon megapot stock pot sold on this site on the burner. I was wondering if anyone with experience could give me an estimated burn off rate for a 60 min boil (and a 90 min if anyone has an answer for that) so I can determine how much pre-boil wort to shoot for. I will be doing a full volume boil btw.
There are numerous factors for boil off but I’m pretty sure the burner has NOTHING to do with it. It might take some fine tuning as far as heat goes so make sure you keep a good boil.
In my experience it has a lot more to do with kettle geometry than the burner. I notice a fair bit more boil off with my very wide boil kettle vs. my narrower, taller Blichman kettle. Even within the same pot I notice little difference it volume boiled off when I’m doing 5 gallon vs. 10 gallon batches if I keep the rate of boil about the same. Makes sense to me since using the same pot the same amount of liquid is exposed to air regardless of how much I’m boiling.
FWIW, I boil off about 0.75-1.25 gal/hr using my Blichmann Floor Burner + Blichmann 10 gal kettle. The variability is due to how hard a boil I’m at.
I mention the kettle explicitly because, as others mentioned & rightly so, the geometry is likely to play a significant factor (and the Blichmann kettles are relatively taller & narrower than the megapots, meaning less surface area and less boiloff).
I use the same brew kettle, and I boil off somewhere between 1 and 1.5 gallons during a pre boil steeping of specialty grains and a 60 minute boil combined.
Outside temperature and humidity also have a hand in this…so, I always shoot on the high side and anticipate 1 to 1.5 gallons per hour (but I have a converted keg - keggle as my main boil pot and a 7.5 gallon Italian stainless pot as my backup for 5 gallon batches). Both are wider than the Blichmann 10 gallon pot, so I would shoot for a 1 gallon per hour boil off as a guesstimate.
