Cooler loses 10 degrees in an hour. Good enough?

[jaobrien6]

I have a coleman 28 qt. cooler that I wanted to turn into a MLT. I just tested it out to see how well it holds temp and it lost 10 degrees (150 -> 140) in an hour. Is this good enough or do I need a better insulated cooler? I'm just learning and getting into AG brewing, so I don't have any experience to go off of at this point.

Thanks!

Edit: this was tested with just plain water, not sure if that will make any difference in how much heat is lost compared to a mash with grains.

 

[Whiskey]

That seems like alot. I have a "standard" Rubbermaid 10g that only looses 1 degree @ 70F ambient in 1 hour.

How much head space did you leave for the test?

 

[BargainFittings]

The lid probably does not have foam in it. Get a can of GreatStuff and fill it with foam.

You can lay a towel or two over it until you get the foam in it and that will help slow down the heat loss.

 

[jaobrien6]

That seems like alot. I have a "standard" Rubbermaid 10g that only looses 1 degree @ 70F ambient in 1 hour.

How much head space did you leave for the test?

A lot, it's a 7 gallon cooler and i only had 2 gallons of water in it. I didn't think of it, but that would probably make a big difference.

 

[blackwaterbrewer]

did you pre heat the cooler before your test? 10 degrees per hour temp loss is way too much.

 

[jaobrien6]

The lid probably does not have foam in it. Get a can of GreatStuff and fill it with foam.

You can lay a towel or two over it until you get the foam in it and that will help slow down the heat loss.

You're right, it does feel like it's hollow. I can try that, too. So maybe I should put some foam in the lid and then test again with 4 gallons or so of water, to better approximate the mash water + grains for a 5 gallon batch of beer?

 

[jaobrien6]

did you pre heat the cooler before your test? 10 degrees per hour temp loss is way too much.

I didn't preheat, but I took the 150 degree test after it'd been in the cooler for 3-4 minutes, I figured that was good enough to stabilize the temp of the cooler. Was that an incorrect assumption do you think?

 

[blackwaterbrewer]

i dont know for sure. try putting 1-2 gallons of boiling water in. shake it up and let it sit for 10 min. then do your test. if the lid is hollow, though, that is most likely the problem.
you shouldn't lose any more than 1, maybe 2 degrees in 1 hour.

 

[Donner]

10 degrees sounds like the amount of heat my 7 gallon absorbs. I usually fill it with hot tap water while my mash water is heating. Put a couple of gallons in and swirl a bit. Let sit while the mash water comes to temp.

With this method i didn't lose any heat when i mashed in. During my 'tests' i noticed that without preheating the thing would absorb 10-12 degrees of the heat.

 

[jaobrien6]

Thanks so much for all the very quick replies!

Sounds like I should have definitely preheated, and I think i'll insulate the lid too 'cause it can't hurt. I'll test it again, but sounds like it should work fine as long as I preheat it.

 

[Donner]

keep in mind preheating doesn't really take that much. You just need to raise the temp of the walls such that the difference between your mash and the tun isn't that great. a 70 degree cooler will eat up a lot of heat whereas a 100 degree or better cooler wont.

Running hot water down the sides and then putting the lid on the cooler will help more than you can imagine.

 

[bendavanza]

+1 to Donner
I take 1/2 gallon or so from the HLT or a teapot and pour it down the sides, put the lid on, and wait 5 minutes or more before I drain and refill for the strike water. I may try foaming the lid on mine, too, I had not considered it may be hollow. I usually lose about 10 degrees from HLT to MLT and around 10 more when I dough in, depending on the grain bill, and lose no more than 2 degrees, usually just 1, over the hour.
-Ben

 

[Nwcw2001]

Two quick points.

1. Preheat: but only with strike temp. Because boiling water will warp your cooler. This will preheat the cooler fine.

2. Adding grain will help the heat retention of your cooler. It will increase the thermal properties you're looking for.

I found that my cooler lost 4 degrees over an hour when preheated and grain added.

John

 

[Hophazard]

Adding grain will help the heat retention of your cooler. It will increase the thermal properties you're looking for.

+1

My cooler MLT lost about 7-8* when I tried to test with just water. Once I added the grain and covered the lid with two towels, I only lost 1* in an hour.

 

[jaobrien6]

My cooler MLT lost about 7-8* when I tried to test with just water. Once I added the grain and covered the lid with two towels, I only lost 1* in an hour.

Just as a follow up for anyone who stumbles across this thread. I finally got around to making my first AG batch, and used the mash tun I was referring to in this thread. With almost 14 lbs of grain and 4.5 gallons of water, the mash tun was pretty close to full. With this volume of mixture in the cooler to hold the heat, it worked perfectly. Dropped *maybe* a degree, maybe only half a degree (my digital thermometer only displays in 1 degree increments) over the course of an hour.

All in all, it worked like a champ. So the moral of the story is that testing a cooler style mash tun with just a couple gallons of water is not a good test.

 

[wilserbrewer]

OK good job...just have to add that IMO almost any cooler properly preheated will hold plenty of heat and work well for a mash tun. But if you are so inclined to insist on mashing outdoors during a frigid blustery day...go ahead and get an "exteme" cooler.

 

[mattmcl]

I throw a sleeping bag over mine in cold weather, you can always find them on Craig's List.

 

[Baldy_Beer_Brewery]

If you try to insulate the lid with Great Stuff, keep in mind that it swells enough to warp some lids. They make it in a flavor that doesn't apply as much force to the surrounding areas to keep doors and windows from sticking, I'd use that.

 

[bmckee56]

I have a 5 gallon igloo cooler that I fill with 120F. water (4 1/2 gallons from the hot water tank). I hit and hold my temps throughout the entire mash when preheating the mash tun.

I am looking now to pick up a 10 gallon cooler for larger batches and use the 5 gallon for smaller batches.

Salute!

 

[chuggs]

Do a search for a Heat stick...

It's a handy thing to have when using coolers for mash tuns.

I usually give a quick stir with mine once or twice during an hour mash...and keep the temperature within a degree or two the entire time.

 

[Xakk]

On a side note, you may find that a 7 gallon cooler will run out of space in a hurry. I've got a 10 gallon rubbermaid and there have been several times I wasn't sure it'd all fit. I max out at around 22lbs of grain depending on how thick I mash. Just food for thought.

 

[jaobrien6]

On a side note, you may find that a 7 gallon cooler will run out of space in a hurry. I've got a 10 gallon rubbermaid and there have been several times I wasn't sure it'd all fit. I max out at around 22lbs of grain depending on how thick I mash. Just food for thought.

Yeah, you're right. I went with the 7 gallon because I had one lying around, if I had to buy a cooler, I would have gone bigger. I can probably squeeze 15 lbs of grain in. If/when I want to make any bigger beers, I guess I'd just have to do a 4 gallon batch or something (haven't done the math, not actually sure)... at least until I move to a bigger mash tun at some point.

 

[chefchris]

Headspace is also a factor. I have a huge cooler but usually do 5 gallon batches. I got a piece of styrofoam cut to the size of my tun and I place it on top of the grain bed. Cuts down on the head space.

Just throwing in another tip.

 

[limulus]

Headspace is also a factor. I have a huge cooler but usually do 5 gallon batches. I got a piece of styrofoam cut to the size of my tun and I place it on top of the grain bed. Cuts down on the head space.

Just throwing in another tip.

Exactly what I used to do.

 

[JKoravos]

Just a note: It's best to preheat your cooler with water at your desired mash temperature. If you use hotter/colder water then the cooler will still either absorb/release heat into the mash. I preheat my cooler with my strike water, which is usually in the mid-160s. I still have to account for the heat gained by the mash from the cooler, even with only a ~15 degree differential between the preheat water and the mash temp.

 

[Brew-boy]

The lid probably does not have foam in it. Get a can of GreatStuff and fill it with foam.

You can lay a towel or two over it until you get the foam in it and that will help slow down the heat loss.

A+ this is what fixed mine, I only loose 1 degree in an hour now.

 

[JesseRC]

Just a note: It's best to preheat your cooler with water at your desired mash temperature. If you use hotter/colder water then the cooler will still either absorb/release heat into the mash. I preheat my cooler with my strike water, which is usually in the mid-160s. I still have to account for the heat gained by the mash from the cooler, even with only a ~15 degree differential between the preheat water and the mash temp.

I disagree. For simplicity sake, it's best to overshoot your Strike water temp (to maybe 175 F or higher). Then add it to the cooler. Close the lid, allowing the cooler to heat up. Then just wait for the water temp to drop to the strike temp(based on some mash calculator), at which point you can add your grains. I've had great success with this and there's no need to preheat your cooler with additional water.

 

[JKoravos]

I disagree. For simplicity sake, it's best to overshoot your Strike water temp (to maybe 175 F or higher). Then add it to the cooler. Close the lid, allowing the cooler to heat up. Then just wait for the water temp to drop to the strike temp(based on some mash calculator), at which point you can add your grains. I've had great success with this and there's no need to preheat your cooler with additional water.

I do exactly this and my mash temp comes in 1-2 degrees higher than ProMash calculates for a vessel with 0 thermal mass. Strike water calculations only take into account the energy in the water (if you're using 0 thermal mass for your MLT), if the cooler is holding excess energy, it will also transfer to the mash.

 

[JesseRC]

I do exactly this and my mash temp comes in 1-2 degrees higher than ProMash calculates for a vessel with 0 thermal mass. Strike water calculations only take into account the energy in the water (if you're using 0 thermal mass for your MLT), if the cooler is holding excess energy, it will also transfer to the mash.

That may be true, but you can also get the +/- 2 deg if you over mix or under mix your grains. If I notice I am over a bit, I just mix for minute or 2 and the temp drops and stablilizes. I'm just saying that its a pretty easy way to mash in doin it this way, albeit you have to wait a bit for it to reach strike temp.

 

[wildwest450]

That may be true, but you can also get the +/- 2 deg if you over mix or under mix your grains. If I notice I am over a bit, I just mix for minute or 2 and the temp drops and stablilizes. I'm just saying that its a pretty easy way to mash in doin it this way, albeit you have to wait a bit for it to reach strike temp.

+1, it's always easier to stir out a degree or two, than to raise it.

And don't ever put boiling water in a cooler, unless you want a shrinky dink.

 

[elmetal]

so for filling the lid with great stuff, do I want to cut a hole in the lid and fill on the inside or just put a layer literally under the lid?

 

[JKoravos]

That may be true, but you can also get the +/- 2 deg if you over mix or under mix your grains. If I notice I am over a bit, I just mix for minute or 2 and the temp drops and stablilizes. I'm just saying that its a pretty easy way to mash in doin it this way, albeit you have to wait a bit for it to reach strike temp.

I agree, it's probably the easiest way to mash-in in a cooler. I have just learned to know a degree or two off my strike water.

 

[cabledawg]

so for filling the lid with great stuff, do I want to cut a hole in the lid and fill on the inside or just put a layer literally under the lid?

I have not used a mash tun before but I would cut a hole in the outside top of the lid and fill. Cutting the hole in the underside of the lid and filling the lid might lead to issues.

 

[wildwest450]

I have not used a mash tun before but I would cut a hole in the outside top of the lid and fill. Cutting the hole in the underside of the lid and filling the lid might lead to issues.

+1, if you just cake it to the underside your going to cut down considerably on your amount of grain and water space.

 

[cabledawg]

Plus if you just spray the underside of the lid, that might add some wicked chemicals to your brew if your wort comes in contact with it.

 

[JesseRC]

I would go to the hardware store and find some plastic plugs. Then drill 4 holes and spray it in via those holes then plug the holes. But seriosly, why not just try a few batches first b4 doing the modifications