Boil off rate - looking for input

[Spicemon1972]

Ok guys, I know that this has been brought up before but I'm hoping some of you may have some input for me.
Background:
I got a 30qt aluminum turkey fryer for Christmas (Bass Pro Shop model) and today I decided to get outside and boil some water to determine my boil off rate as well as get an idea of how long the burner will take to get a full volume to boil. I started with 6.5 gallons of water and turned on the burner at max output. It took about 52 minutes to get to a rolling boil with an ambient temperature of roughly 27 degrees outside. I boiled for 45 minutes, dropped in my 50ft 3/8in od copper chiller and boiled for another 15 minutes. Then I turned off the burner and chilled the water down to 65 degrees in about 12 minutes. I removed the chiller and measured what was left of my water. I found that I had 4.8125 gallons remaining. This gives me a boil off rate of 1.6875 gal/hr including any loss from transfer and removing the chiller etc.
My question is does this sound like a reasonable boil off rate for the situation I have described? Seems quite high to me as I expected to lose at most 1.25gal in an hour.
Any and all input & suggestions will be greatly appreciated.

Cheers!

 

[ChrisJPassarelli]

I think that's certainly higher than you would WANT it to be, but this thing has an adjustable gas flow, right? Turn it down a bit if you can do so while still achieving a healthy boil. I imagine I could achieve that rate too with my burner on high, but I don't think I've ever had to run it at full output and I tend to get the 1.2 gallons you mentioned.
So! Turn down the heat a bit, make sure you've got a low enough mash pH and enough calcium in there, and you should still get a perfectly nice break.

Out of curiousity, how did you get such an oddly specific volume amount? "A little less than 5 gallons" might be more accurate.

 

[Spicemon1972]

Thanks for the tip - seems as if I floored it just like having a new car and drove that sucker hard.
When I brew tomorrow, I will be sure to go wide open until I reach a boil then ease it back to maintain the good, rolling boil.
As for the measurement, I transferred a gallon at a time until I didn't have a gallon left then I poured the rest into a container that I weighed first (so I knew its weight) then I weighed the rest of the water and converted the weight to volume using the good old "a pint is a pound, world round" conversion. Tricky, huh?

 

[ChrisJPassarelli]

Ah, very nice! Makes sense. Good luck on the brew!

 

[1MadScientist]

~ 1.38, other factors play into it like humidity too.

 

[LKHA]

ambient temps/humidity good luck nailing it

 

[jhall4]

That makes sense given the, as others have mentioned, cold air and low humidity. About the only think you can do is back off until your barely rolling instead of vigorously boiling and wait for it to warm up.

 

[Spicemon1972]

I brewed this weekend and paid special attention to keeping the boil with the least flame I could (as opposed to running wide open the whole time). Definitely helped - still lost a little under 1.4 gallons during the 1 hour boil, but as has been said, the cold air and low humidity likely didn't help. Fortunately I started with 6.75 gallons and wound up transferring a little over 5.25 gallons which, after fermentation is done and I rack to secondary then condition and bottle, should give me right around 5 gallons of finished beer. Yay!
Thanks for all the input - much appreciation!