Temp stability in 10 gallon beverage cooler

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mjohnson

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I'm pretty sure there was a thread that mentioned something abou this, but I'm having some trouble with temp stability in my 10 gallon home depot beverage cooler.

I've done 2 all grain batches, each with about 10lbs of grain, so there was a decent amount of head-space. I preheat my tun with 180 water for a good 15 minutes or so and hit my strike temps more or less. However, I'm losing about 5-6 degrees over the course of an hour.

I've read that some folks use expanding foam in the lid. Does that make all the difference? I keep reading people saying, "I only lose 1 degree an hour"

Anyway, I'm not stressed about it. I still made beer. But I'm wondering what I can do to reduce the temp fluctuations.
 
I have the Rubbermaid 10 gallon cooler - which I guess is basically the same. I only loose about 1 degree over the mash.

Do you preheat the cooler first with hot water? You could try wrapping it in blankets or insulating material.
 
Yeah, I gave it a good 15-20 minutes of 180F water. The sides of the cooler are cool (even with hot water) but the lid is warm. I'm guessing its a combination of headspace and bad insulation on the lid. Is there a clean way to fix these things?
 
I put some expanding foam in the lid of mine. Seems to work well even if I feel some heat coming up. Lose maybe 2 over 60 minutes. There is also the question of mass. 20lbs of grain in a 10 gallon cooler should stay constant as compared to 10 lbs cause of all the headspace above.
 
I have done 10 lbs of grain in a 48 qt rectangle cooler and only lost 1-2 degrees per hour for the mash. I insulated the lid to my mlt. Its called Great Stuff and they sell it at the home improvement stores. Put it in the lid, it will make a difference. I also throw a blanket over the mash and check the temp once, at 10 mins in to verify the mash temp. then let it sit for the rest. I just drilled a couple holes in the lid and applied the foam in and covered the hole with some duct tape.
 
are you opening the tun up repeatedly to check temps? That'll get you every time. You lose a lot of heat each time you open it up.
 
Try heating your strike water a few degrees over the calculated temperature. Fill your mash tun and wait about 5 minutes. If it hasn't dropped down to the calculated temp, give it a vigorous stir and wait a bit. Repeat until you're where you want to be and then add the grains. It should hold better after that.
 
I use a "float".

Take a piece of 3/4" foam board, cut to fit snugly into the cooler. Make a loop handle out of a zip tie. When you go to use it, cover in saran wrap. Poke a probe thermometer through the float to check the temp.

The float floats on top of the mash, holding in the heat.

I tend to lose less than a degree in an hour, even in the winter.

:ban:
 
I use a "float".

Take a piece of 3/4" foam board, cut to fit snugly into the cooler. Make a loop handle out of a zip tie. When you go to use it, cover in saran wrap. Poke a probe thermometer through the float to check the temp.

The float floats on top of the mash, holding in the heat.

I tend to lose less than a degree in an hour, even in the winter.

:ban:

That is an excellent idea! I know what to use my left over foam board for.
 
Great idea Kirk! I've been in the same boat as mjohnson. When I insulated my top it did help a bit. I've been blown away that some folks only loose 1 degree and maybe this will get me into the 1 degree club.
 
are you opening the tun up repeatedly to check temps? That'll get you every time. You lose a lot of heat each time you open it up.

Nope. I have a polder probe thermometer that I jam into the grain bed and run the cable up through the lid - so the lid is screwed on a little loose for the cable, but I don't think its enough to account for the 5 degrees. Maybe I'm wrong.

Good idea on the foam board. Is there any concern with off flavors from the foam? I suppose I could just buy a styrofoam cooler and cut that up...
 
Nope. I have a polder probe thermometer that I jam into the grain bed and run the cable up through the lid - so the lid is screwed on a little loose for the cable, but I don't think its enough to account for the 5 degrees. Maybe I'm wrong.

Good idea on the foam board. Is there any concern with off flavors from the foam? I suppose I could just buy a styrofoam cooler and cut that up...

That's why you wrap it in saran wrap. I use multiple layers, from different angles, to make sure the foam is well covered. After the mash, just remove the wrap and pitch it.

I'm working on a keggle MLT, which will have a LOT of headspace. Making a float for that will be interesting.
 
chemman- Yes. Every time you open the lid you bring in fresh air to the headspace.
mjohnson- Yes, great stuff foam in the lid does help. I just drilled 2 small holes (one on each side) on the top of the lid and filled it as much as I could, sort of shaking it back and forth to spread the foam around. Expect to have foam worms coming out of the lid for a while, they are a mess, and nothing gets this crap off of your skin or clothes. It expands a LOT.
 
I just bought a 10 gallon cooler, and plan on filling the lid with expanding foam as described above. Any reason I can't blow the rest of the foam into a food grade plastic bag to create my float? I'm planning on pulling the center of the bag up and pushing a pen through while the foam sets to create a hole through the float in such a way that the bag will be the only thing to contact the thermometer/wort.
 
I have yet to do another brew, I plan on filling the lid of my tun with that foam. Hopefully this will help me hold temps. Its annoying because I hit my temps exactly at the beginning of the mash and then at the end its 5 degrees lower or so and leads to a more fermentable product which over dries some of my beers
 
I have just started to lose heat through the mash in my 10 gal cooler...it was perfect for about 15 or so brews, then the past three times Ive used it I'm losing 5-7 degrees over an hour and a half mash....wtf?
other variables haven't hanged enough to warrent this new temp drop... Im puzzled why this is happening...I will have to pull the ball valve and check to see that water/wort hasnnt gotten into the insulating foam...that would cause a drop like this I believe.
 
any other thoughts?
I don't know what type of thermometer you are using but since this just started happening after 12-15 batches do you think it could be the thermometer and not the cooler? In my experience those cheap electronic thermometers I use on my grill only last about one summer before they either don't read at all or are not calibrated with a dial meat thermometer...just a thought.
 
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