My Evaporation is Unreal - Unbelievable almost, WHY?

[switzead]

I am getting anywhere between 23 and 30 percent evaporation rate during my boil.  I make 5.5 gallon batches in a 12 gallon pot, 17 inches in diameter.  I live in Corpus Christi TX, usually 85-95 degF and 85-95% humidity.  I boil in my garage with a small overhead ceiling fan on medium speed.  To me this seems to be too much evaporation but it has been this way for 3 years now.  Whats going on, any thoughts?

[MaltLicker]

A 12-gal, 17-inch pot would be on the high-end of evap rates.  Have you boiled plain water and measured precisely?  About 7.5 gals down to 5.5 gals? If you want to evap less, boil shorter or less vigorously?

A friend with a similar 15-gal, 18-inch pot regularly takes 8 gals down to 6.5 gals in 90 mins.

[UselessBrewing]

The more vigorously you boil the more evaporates. The fact that you have a fan with constant air movement also helps because it has better foam control, and you are less likely to boil over. Therefore you can crank up the heat. This is purely speculation on my part, but makes sense. I'm in Houston so I am sure the weather has very little to do with it. I use a Keggle for 5G and 10G batches, and I have noticed more evaporation on the 5 g batches than the 10, mainly because I have more head room and crank up the heat.

Cheers
Preston

[switzead]

8 gallons to 6.5 gallons in 90 minutes is only 12.5%/hour.  I am seeing double that in an hour.  I do boil with the fire at full rage because I have the room in my pot to do so.  I have never had a boil over.  It is not a big issue as I account for it when I brew.  My problem is that I will run out of sugars in my mash before I hit my needed volume.  I usually then just top it up to boil volume with plain water.

The boil off is not my major issue.  My issue is that I get all the points I need from my mash before I get my total boil volume, or I will run out of sugars in the mash before I get my boil volume.  In these case I have been adding plain water (if I have all the points I need) or I add water and DME (if I need some additional points).  Either way it seems I am dilluting the wort before I boil it.  Is this the way to do it or should I be doing it another way?

[Wildrover]

My guess is the full rage boil.  I use the bayou burner in my garage and it is barley open when I boil. I'm usually around 9-10% maybe a little more when I boil.  Next time, right before the hot break, try turning the heat down and I bet you'll lose a lot less. 

I know a lot of people will poo poo this but I go by having just enough boil to show a little violence.  I've heard that you want as vigorous a boil as possible but I don't buy it.  I know you want some violence to drive out the DMS but anything after that is overkill in my opinion.  I have never had any issue with off flavors or "egg" smells or anything.  I also think I get some savings in the greater gas efficiency. 

$0.02