Temp Drop with Cooler MLTs

[uwmgdman]

Hey everyone....

After doing partial mashes for the past couple years I finally bit the bullet and did my first all grain on Sunday. The brew day went pretty well, my efficiency was low, around 60%, but that's fine, I've got some ideas of things to do differently next time. I've got 5.5 gallons of wort fermenting happily.

My biggest concern is the temp drop I experienced in my 10 gallon rubbermaid MLT. When heating mash water, when it was about 150F, I dumped a gallon or so in the MLT let it sit and sloshed around for 3 or 4 minutes, returned to the rest of the mash water and covered the MLT. I added my mash water to the MLT at 164F. (Which was my strike temp based on 12.5lb grain and 1.5 qt/lb ratio.) The temp settled at 151/152F after a real good stir. After about 30 mins the temp had dropped to 148/149F. I microwaved a quart of water into the 160s (my sparge water I was heating wasn't hot enough yet and I was too impatient to wait for the microwave to boil a quart of water). I did the same thing 10 minutes later. The temperature came up some but still settled around 147F.

Does this temp drop seem too large? The outside temperature was 30F. I think what I will do next time is heat my mash water about 10F above the strike temp and let it naturally come down to strike temp......which will warm the tun better. I think my method of preheating the tun may have been insufficient.

Any comments about the temp drop........it seems too large, you guys agree? I wasn't sure what to expect with the cold outside temperatures. I know I'll have a very fermentable brew, but that's fine, I'm using a lower attenuating yeast so it should balance out.

 

[EdWort]

I add a couple gallons of 170 degree water and close the lid for at least 10-15 minutes and it will hold the temp for 60 minutes without a drop. You will want to do this inside too. The outside temp plays a huge role here.

Sounds like you are not preheating long enough. Don't use boiling water though, you will warp your cooler.

 

[FlyGuy]

+1 that you probably aren't preheating long enough. Big coolers need lots of time to equilibrate in temperature. I bet your temperature loss wasn't due to heat escaping, but rather, to being absorbed by the cooler.

I adjust my strike water to account for both heat absorption by the grain and the cooler (lots of software out there to do this). I let it sit in the cooler for about 10 mins or longer (until the temperature completely stabilizes). If it is spot on, then I add the grains. Much easier to adjust the water temps BEFORE you add the grain than after.

Oh, also, I use a couple of 10 gal Rubbermaid coolers, and once they are preheated and temp equilibrated, they lose about 1 degree of temp for a typical 5 gal batch.

 

[uwmgdman]

Oh, also, I use a couple of 10 gal Rubbermaid coolers, and once they are preheated and temp equilibrated, they lose about 1 degree of temp for a typical 5 gal batch.

I see you're in Canada......do you brew outdoors or indoors? As EdWort suggested, do you notice a difference in terms of temperature drop during the cold (assuming you brew outside) vs. the warmer season(s)?

Ed, do you always move your mash inside after you've got everything doughed-in?

 

[Blender]

I would agree with the posters above in that 3-4 minutes to preheat is not long enough. I let mine preheat for 15 minutes or so while I grind the grain and heat the strike water. You can also throw a big towel or blanket over the top and it will help keep the heat in as most of it escapes through the lid.

 

[maltMonkey]

Make sure you record EVERYTHING when you are doing your first several brews. The ambient temperature, your hot liquor temp, how much it dropped initially after pouring into your MLT, how much it dipped after 10 mins, grain temp, ect. If you keep records of all this stuff it will give you the info you need to nail all your temps regardless of the ambient temp.

It took me several tries before I could start predicting what would happen at a given temp.

Another thing I do is to always err on the side of temps that are too high. I keep a pitcher of cold water nearby, and it's very easy and fast to adjust down a temp, but it's a lot harder to adjust up.

 

[Quercus]

I brewed on my new system this weekend, also utilizing a 10-gallon cylindrical cooler.

I pre-heated with about 1.5 gallons of 170-degree water. I put the lid on tight, sloshed it around several times, and let it sit for a good 15 minutes.

Then poured out the water, added the grain, went in with my strike water at 170 degrees at 1.25 qts per pound, and hit the mash temp dead nuts at 152 degrees.

One hour later, it was still at 152 degrees. Keep in mind, this is in Northern California, and it was about 60 degrees and sunny yesterday. I would imagine that ambient temps play a huge role in heat loss, even with an insulated cooler.

 

[EdWort]

Ed, do you always move your mash inside after you've got everything doughed-in?

Nope, only if it is very cold outside. I have not brewed on a cold day yet in Austin this year, so I've enjoyed our mild winter down here.

 

[FlyGuy]

I see you're in Canada......do you brew outdoors or indoors? As EdWort suggested, do you notice a difference in terms of temperature drop during the cold (assuming you brew outside) vs. the warmer season(s)?

I brew indoors in the winter. I would expect to lose a bit more heat if I mashed outside in the cold. I have brewed in a 40'ish degree F garage a couple of times, and saw the cooler lose about 3 degrees over an hour.

 

[springer]

The 10 gallon Igloo I use dropped 2 degrees in 75 minutes Ambient air temp was 44 ( unheated detached garage ) I did notice that the sides were cool and the lid and spigot were warm so I assume most of my heat loss was from the two. The grains were 74 degrees when I mixed them into the strike water.


I did use a lot of water to pre heat the tun and let it sit for a good 15 minutes I also used a higher temp than the strike was dont know if that did anything but it couldnt hurt . Then used the water for my sparge about 4 gallons.