MLT (cooler) heat loss issue

[GoNova]

Guys,

Just finished my DIY MLT (rock on flyguy :rockin. My issue is that I am losing much more heat in my 10 gallon rubbermaid cooler than I anticipated. I did a dry run tonight with these (disappointing) results:

Started with 3 gallons of practice strike water at 162 degrees (I'm making 5 gallon batches now). I did not add any grain.
After 10 minutes the water was at 156 (which was anticipated because I didn't preheat the cooler)
After 1 hour the water temperature was 148!

Not good. I was only expecting to lose a degree or two. Will the grain help stabilize the temperature? I really don't want to hassle with constantly adding hot water and stirring.

I was SO excited to build my MLT, but now I'm pretty disappointed.

Any ideas??? Thanks fellas.

 

[Germelli1]

I think that is completely normal. The specific heat capacity of the grains should help trap and hold in heat much more than water alone. When you do brew, make sure you account for the heat required to bring the grain bed up to temp...not just preheating the tun!

 

[tunoffun]

I'm guessing the main problem with your test was the lack of volume. I've only done one 10 gallon batch w/ my new cooler tun (10 gallon rubbermaid), but after an hour, the temp had only dropped 1 degree. And that was brewing outside w/ a storm literally brewing around me.

 

[Gregscsu]

Your mash tun being only 30% full also conributed to you rapid heat loss. The fuller the mash tun to slower the heat loss.

 

[Ohio-Ed]

How warm was the lid of your cooler? Most of the round lids are hollow and don't hold heat real well. You might test again with something on top to insulate the lid.

I also agree with the other posters that a 30% full cooler will likely have more loss that a full one.

Some folks have cut a Styrofoam "disk" to float on top of the mash to keep heat in which could account for both situations I mentioned.

Ed

 

[rico567]

I don't see the results in the OP as being anything to get excited about. I have used the 10 gal. Rubbermaid / HD "Big Orange" cooler (with Bargain Fittings braid conversion kit) for 16 months now, and am having uniform, predictable results*.

*Notes:

1. I preheat with 3 gal of H2O at 170F. Two hours later, water will be 146-147F.

2. I filled the lid (which is completely hollow, no reason to insulate a lid in a cooler, since heat goes UP, right?) with that Great Stuff spray foam insulation.

3. I cover the MLT with a furniture pad for extra insulation while preheating / mashing.

4. I keep the brass ball valve covered with a foam block to help control heat escaping at that point.

5. I will lose 1-2 degrees in an hour's mash with this system, which is negligible.

 

[GoNova]

Thanks guys. Great points Rico and Ed. I did notice that my lid was very warm. And the lid is hollow. Great Stuff sounds like the way to go. I'm wondering how many holes I need to drill on the top of the lid to completely insulate the lid?

Appreciate all the comments/suggestions!

 

[Sreidy12]

When I made my first MLT out of a cooler I had the same problem; did a test run with just water, the temperature dropped about 10-15 degrees over an hour, and I freaked. After doing a little research I found an article about thermal mass. Thermal mass is an item's ability at maintain heat and minimize fluctuations in temperature. Properties required for good thermal mass include high density and high specific heat capacity. Adding grist to the water brings a considerable amount of both to the table. I was very pleased after I did my first batch to find that I had only lost 1 degree over the course of the 1 hour saccarification rest instead of the 15 I had lost with just water. Anyways, hope that helps!

 

[Cpt_Kirks]

How warm was the lid of your cooler? Most of the round lids are hollow and don't hold heat real well. You might test again with something on top to insulate the lid.

I also agree with the other posters that a 30% full cooler will likely have more loss that a full one.

Some folks have cut a Styrofoam "disk" to float on top of the mash to keep heat in which could account for both situations I mentioned.

Ed

Yeah, pre-heating and the float are the keys to holding in the heat. I lose less than a degree in an hour, with 5 or 10 gallon batches using these methods.

:rockin:

 

[sgillespie]

Same thing happened to me the first time I mashed in my MLT. Started at 155 and ended up at 148 or so. The next time I just put a couple of towels on top and that helped a ton.

 

[Ohio-Ed]

Thanks guys. Great points Rico and Ed. I did notice that my lid was very warm. And the lid is hollow. Great Stuff sounds like the way to go. I'm wondering how many holes I need to drill on the top of the lid to completely insulate the lid?

Appreciate all the comments/suggestions!

I have read posts from folks that have concerns with using GreatStuff for insulating cooler lids. I think the theory is that if you get condensation in the lid and it drips back into the mash through the weep hole in the top that it could leach undesirable stuff back into your mash.

You can make your own call...

Ed

 

[BendBrewer]

Same thing happened to me the first time I mashed in my MLT. Started at 155 and ended up at 148 or so. The next time I just put a couple of towels on top and that helped a ton.

It's spelled TUN. :cross:

 

[rico567]

I have read posts from folks that have concerns with using GreatStuff for insulating cooler lids. I think the theory is that if you get condensation in the lid and it drips back into the mash through the weep hole in the top that it could leach undesirable stuff back into your mash.

You can make your own call...

Ed

Yep.....and I made mine. I think the theory you cite is on the same order as HSA (Hot Side Aeration), the need to secondary, and other things. My favorite is that once stainless fittings and chillers started to become commonly available, suddenly copper and brass were some big threat to the beer. None of this stuff was ever proven, and until proven, I'll regard it as speculation, period.

 

[Ohio-Ed]

I have read posts from folks that have concerns with using GreatStuff for insulating cooler lids. I think the theory is that if you get condensation in the lid and it drips back into the mash through the weep hole in the top that it could leach undesirable stuff back into your mash.

You can make your own call...

Ed

Yep.....and I made mine. I think the theory you cite is on the same order as HSA (Hot Side Aeration), the need to secondary, and other things. My favorite is that once stainless fittings and chillers started to become commonly available, suddenly copper and brass were some big threat to the beer. None of this stuff was ever proven, and until proven, I'll regard it as speculation, period.

My reply was to the OP... I'm aware you made your call; I was suggesting the OP might want to consider doing a bit of research and make his own decision.

 

[tunoffun]

My favorite is that once stainless fittings and chillers started to become commonly available, suddenly copper and brass were some big threat to the beer. None of this stuff was ever proven, and until proven, I'll regard it as speculation, period.

Brass does leach lead into ordinary water. That's not speculation... it's a proven fact. It's also a proven fact that increasing the acidity of the solution - as with wort - substantially increases this leaching.

What's open to speculation is whether the use of brass in common home brewing systems leaches amounts worth worrying about.

Personally, I'd rather ere on the side of safety.