Loosing too much heat in mash tun

[safcraft]

Hi all,
I started using my new mash tun yesterday, brewing a dunkelweissen.
Its a brand new coleman cooler 70qt extreme.
I changed the tap valve , other than that no tweaks.

I used 8lbs grain bill for 12l (3.2 gal) water mash.
I pre heated the tun prior to inserting the mash water and grain. The tun is quite big, easily would do double the quantity.
I hitted 145F and closed the tun.
Put a aluminium foil on top of grain bed.

The temperature then droped consistently , and after 90min it was at 125F. That s 20f in 90 min....
At this time, i checked for conversion, seemed ok so sparged.
Sparge water raised the bed to 145 again.

So...temps are very unstable. Dont know why... my room temp is around 65F.

Any inputs on what to try? Others seem to be having no problems with similar setups...

 

[jfk69]

That seems like a very large cooler for such a small grain bill. I would lose a little bit in my Igloo 40 quart with that little bit of grain.

 

[tagz]

Yeah. I think if you did a larger batch you would have no problem holding temps. I've found my temps are most stable when I'm filling more than 75% of the available volume.

 

[safcraft]

So i need to find a way to fill the cooler, correct?
To occupy empty space, what kind of material can i use?
Bear in mind that i am not in Usa so, dont know commercial name products.
Those blue foam stuff used in insulating walls are good?

 

[jfk69]

I don't know how that would work either. I would get a smaller cooler or make a bigger beer (or batch of beer).

 

[rgreenberg2000]

I have a similar situation with my MT. I built it out of a very large cooler so that I would have capacity for large grain bills. I didn't want a second MT for smaller grain bills, so I found some rigid foam at HD, cut it to size so it would "compression" fit inside the tun at a level that was good for my usual grain bills (the sides of my cooler slope inward a bit, so it was easy to cut to a size that would wedge in securely.)

So, I mash in, insert foam, then top that with towels, and close up the lid. I can hold my mash temperature within a degree for at least 90 minutes.

R

 

[MollyHatchet]

I have a Coleman 70 quart extreme cooler I use as a mash tun. I ALWAYS preheat my mush tun to 170F, in Beersmith you can add this temperature and it will automatically calculate your strike temperature water. You also need to take temperature of your grain and add that into the calculation.

A cold mash tun, and using a strike water temperature that low is just asking for problems. I am not sure what you are brewing, but my strike temperature after dough in is NEVER below 147F-148F. Also usually my smaller batches are 9.5-10 lbs of grain, and I never fall below one or two degrees from strike temperature, and even if it does, conversion is pretty much done by then. I never used, or needed to use foil on the grain bed. I hope that helps, and good luck with your future brews. CHEERS!!

 

[Chrisl77]

I have a similar situation with my MT. I built it out of a very large cooler so that I would have capacity for large grain bills. I didn't want a second MT for smaller grain bills, so I found some rigid foam at HD, cut it to size so it would "compression" fit inside the tun at a level that was good for my usual grain bills (the sides of my cooler slope inward a bit, so it was easy to cut to a size that would wedge in securely.)

So, I mash in, insert foam, then top that with towels, and close up the lid. I can hold my mash temperature within a degree for at least 90 minutes.

R

This is what I did when I had my rectangular cooler. The only thing extra I did was I wrapped the foam with some foil. It worked well for me also.

 

[cgrivois]

I did this for a while as well but worried about off flavors from the pink foam. May go back to this.

 

[safcraft]

I will try the foam approach next time. Maybe i was not clear, but i do pre heat the MT before dough in.
I wait till it reaches my mash temp and then close the lid.
Maybe 8lbs of grain is not enough to keep temperature, but i find 20f in 90min a lot more than people are reporting.
I will use a blanket around it too next time. Cheers ans thanks for sharing .

 

[tagz]

I don't think a 20 degree loss when you are mashing 3.5 gallons in a 17.5 gallon container is unreasonable. You are only using 20% of the container, thus loosing a ton of heat to the other 80%.

 

[safcraft]

I don't think a 20 degree loss when you are mashing 3.5 gallons in a 17.5 gallon container is unreasonable. You are only using 20% of the container, thus loosing a ton of heat to the other 80%.

So you are supporting the idea of occupying the 80% air gap with some kind of foam insulation to keep the heat in the grain / water ?

I will experiment heat loss with 100% water, to see if there is a difference.
Put 15L of water, and see if i get 20F loss in the same 90 min.
Then fill the tun with 65L of water and test the 90min waiting.

 

[tagz]

Sounds like a good plan. I'd be hesitant to be putting foam or other materials that might heat up and off gas into your wort but I've never experimented with anything like that so take that with a grain of salt.

If you're planning on doing small batches you might just grab a smaller cooler. The 5 gallon igloo coolers only run about $25.

 

[cgrivois]

I found a link last night on the fda website explaining how polystyrene is safe for food service. As I understand it, the pink foam board insulation is polystyrene.

 

[cgrivois]

https://plasticfoodservicefacts.com/main/Safety/Safety-of-PS-Foodservice-Products

 

[safcraft]

I understand the advice on running the MT close to its top volume, but i was truly disappointed to see that a 80$ cooler from Coleman i not holding temps that well. Also, after seeing multiple cases of the SAME cooler being used in similar scenarios (with up to 50% volume usage) and no problems mainting temps.

I do not live in US, i do not have access to 25$ coolers like you have. These items are not common in Europe as in the US.
I will try to find out how to use my 70qt coleman and how to improve temp hold, while still doing small batches of 3-4 gallon.

Cheers

 

[Redlantern]

Just sounds like the cooler is too big. Way too much air to heat up. Foil helps a little but I have a hard time believing it will do the trick. Get a smaller cooler.

If that is truly not possible, then you will probably need to fit Styrofoam to the cooler so it rests on top of the mash

 

[emcfarden]

I've seen on a few threads that these coolers will lose a good amount of heat through the lid if it's not insulated. I've heard of people drilling a hole in the lid and filling it with foam spray insulation ("Great Stuff") to help retain the heat. If your cooler doesn't have an insulated lid you might try that to see if it helps you out.

https://www.homebrewtalk.com/showthread.php?t=236435

 

[evchenko]

I did this for a while as well but worried about off flavors from the pink foam. May go back to this.

You could just wrap the foam in several layers of foil...

 

[Newsman]

If you are going to use the rigid foam board, cut to fit, I would suggest a couple layers of that, possibly wrapped in several layers of aluminum / aluminium foil to help keep the foam from coming in contact with the grain. On top of that, I would also suggest a heavy blanket to help hold the heat in. This is not from experience, mind, just what comes to mind as a way to help reduce the heat loss.

 

[Redlantern]

If you are going to use the rigid foam board, cut to fit, I would suggest a couple layers of that, possibly wrapped in several layers of aluminum / aluminium foil to help keep the foam from coming in contact with the grain. On top of that, I would also suggest a heavy blanket to help hold the heat in. This is not from experience, mind, just what comes to mind as a way to help reduce the heat loss.

Agree with the principal of filling the air space with insulating material - as long as it is safe for use in contact with food.

 

[cgrivois]

You could just wrap the foam in several layers of foil...

I did but still wort come into contact with the foam. After reading up on polystyrene, I am going back to the foam with foil.

 

[ncsuwerewolf]

This is why i have 3 mashtuns. A 5 gallon igloo barrel for small 5 gallon batches. 50 coleman extreme for 10 gallons up to 1.060 and a 70 coleman extreme for 15 gallon moderate gravity or 10 of a large SG. Fill the tun and not lose the heat. I seldom lose more than a degree or 2 in any of my vessels.

 

[safcraft]

I found a link last night on the fda website explaining how polystyrene is safe for food service. As I understand it, the pink foam board insulation is polystyrene.

So i ended up buying polystyrene boards and cut to fit. I can now make a 5 gallon batch in the 70qt coleman cooler, while loosing 2F Degrees only in 90 min mash. Quite happy with that.
I use 2 layers of 4cm thick foam XPS.