calibrating my keggle

I'm getting ready to do a test boil with my new keggle. Up until now, I haven't had the capacity to do 10 gal batches. On average, when you are doing a 10 gallon batch, what volume do you start out with in the BK? For those of you using keggles, how much do you expect to lose to evaporation during a 60 min boil? 90 min boil?

Somewhere around 1.5-2 gallons per hour will evaporate while boiling. It depends on the equipment.

larrybrewer said:

Somewhere around 1.5-2 gallons per hour will evaporate while boiling. It depends on the equipment.

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I second what larrybrewer has posted.

Different people have a different opinion on what's called a rolling boil as I have seen agressive boiling with high evaporation rates vs a undersized burner on the edge below a rolling boil. On that one we used a welding blanket in a hurry wrapped it around the keggle for a big difference in the boil. The other thing is the diameter of the opening will change the boil off rate. My last set of keggles I cut a 10" opening vs 12". Those large diameter short pots expose a lot more surface area for a larger boil off amount. A 12" opening has 113 sq/inch area, 10" has 78.54 sq/inch area which is .694 of the 12". A 16" diameter pot has 201 sq/in surface area that is 2.56 times more than the 10" keggle. This is a reason why I went to 10" on the last keggles and will not own pots plus the kegs are free.

Thanks y'all. Today is a no brew day but it is a build day. Just finished my new MLT made out of a 5 gal igloo cooler. I have it sitting with hot water to see how it holds temps over an hour. Time to go test out the keggle

Dont forget to calculate deadspace, including chiller loss if you use a cfc and fermenter loss. To hit a 10 gallon batch in my bk on a 60 min boil I start with 12.5 preboil. I normally do 12 G batches to take into account of fermenter and secondary loss, which puts preboil to 14.5G. If you push the BK this far don't forget foam control.