How much heat loss to a 10G cooler/mash tun

[95747brewer]

Since I know a lot of brewers out there use the 10 gallon round cooler as a mash tun, could somebody tell me how much they account for heat loss when not preheating the tun? I know ambient temp etc will be a factor, but maybe some ballpark figures or even better a link to a calculator pertaining to this particular cooler would be great. I have done 2 AG batches so far, both with my cooler. The first I guessed and went for 8 deg above may target, and ended up about 2 deg low. The second batch I tried 10 deg above and still ended up about 2 deg low. Both times it was around 55 deg outside (not exact.) I dont have a recirculator so raising and lowering is a step I would like to avoid without 50 trial and error batches that I'm sure somebody has already done. Thanks in advance for any input.

 

[Skoper]

You need to preheat you cooler first. I fill it full with HOT tap water before I start heating up my mash water. I drain and add my mash water in at 165. It add grain and stir the grain until I am 2 degree above my target temp and Than seal her up. I will loose about 2 degree with a 60 minute mash hiting my target temp

 

[Yooper]

If you don't preheat the cooler, there are probably way to many variables to be able to determine the heat loss. Not just the mass of the cooler and the grain (which is constant), but the temperature of the cooler, the ambient temperature, the strike temperature, etc.

Preheating is easy, though. Add the strike water at 175 degrees, and let it fall to your strike temperature. That should take at least 15 minutes. Then, when you hit your strike temperature, add your grain. By doing this, I lose less than 1 degree an hour (indoors) with the Igloo 10 gallon MLT.

 

[95747brewer]

My tap water straight out of the water heater is less than 120. If I preheat with that wont there still be an unknow loss? i've heard of using boiling water but am concerned about the integrity of the tun. I know I could add water from my HLT to raise the temp, but then I am wasting all that heated water when I drain. I just thought there would be somebody who figured out how much this 10 gallon cooler tun (grains not included) absoarbed in heat at intervals of ambient temp. I guess I will continue to trial and error it. My last batch I wanted to hit 170 before the grain addition, so I heated my hlt to 180 and put the called for amount of water for my brew into the tun. Once I dropped to 168 I dumped the water back into my hlt and reheated a little. Once I get my heat stick plugged in I guess my problems will be solved.

 

[annasdadhockey]

+to Yoop's comments.

 

[95747brewer]

I suppose my biggest problem is that my grains were below 40 deg so my strike temp was high, if I remember right 170. I was really hoping to do as Yooper said and add high then bring the temp down, but even using 180 water I went below my strike temp. Should I be leery about going over 180 in an electric HLT built from another 10 gallon cooler?

 

[Bulls Beers]

Once in awhile I forget my grain in the car. When I get them in the morning they are very cold and sometimes can be a problem. I try and keep them at room temp the night before and then do what Yooper does.