Trouble maintaining mash temp with Rubbermaid 10 gal

[HootHootHoot]

I am hoping someone can provide some insight here. Maybe some others use this same set up and might be able to offer advise.

I built my own mash tun following these instructions:
https://www.homebrewtalk.com/f51/cheap-easy-10-gallon-rubbermaid-mlt-conversion-23008/

I've been using it for probably 2 years now. I have been struggling with efficencies. First time I was right at 75%, so I was pleased, but it is all over the place and has gotten as low as 47%. I came to the conclusion that it was due to losing too much temperature in the mash or having trouble with achieving the right temp without going over on my desired strike water volume.

I use beersmith2, which tells me what temp and volume my strike water should be at. I am consistently at a lower temp of about 8 deg.

Last week I heated the cooler with about 3 gallons of hot water before mashing, but I still found myself taking some mash water out, heating it, and adding it back in to achieve my desired temp after about 25 minutes

What gives?


Previously I mashed with just heating my water to 170 deg and adding enough hot and cold water until I reached my desired temp, and my temps held quite nicely. the only down side is if I had trouble achieving that temperature, I would just be adding a lot more water in- more than I needed for a mash. This would increase my wort volume and I ended up with a longer boil just to get down to my desired preboil volume.
BeerSmith 2 seemed to fix this problem, but now I have trouble with mash temps.

 

[Yooper]

I found the same issue for me. I ended up learning that adding about 3/4 of the strike water to the cooler at 180 degrees, and letting that sit for a while, and then adding the rest, and then letting it cool to the strike temperature Beersmith predicted (generally about 11 degrees warmer than the mash temp) worked perfectly.

What I mean is, if I had 3.5 gallons of strike water, I'd add about 2.5 gallons of 180 degree water. I picked 180 because warmer than that warped my cooler . I'd let that sit for about 10 minutes and then add the final one gallon. I'd stir it in, and when the temperature in the cooler was 11 degrees warmer than my mash temperature, I'd add the grain.

That worked so well that I lost about 1 degree per hour in the cooler! I still use the cooler MLT when I have a smaller 10 gallon batch, because I liked that part of it so much.

 

[HootHootHoot]

I found the same issue for me. I ended up learning that adding about 3/4 of the strike water to the cooler at 180 degrees, and letting that sit for a while, and then adding the rest, and then letting it cool to the strike temperature Beersmith predicted (generally about 11 degrees warmer than the mash temp) worked perfectly.

What I mean is, if I had 3.5 gallons of strike water, I'd add about 2.5 gallons of 180 degree water. I picked 180 because warmer than that warped my cooler . I'd let that sit for about 10 minutes and then add the final one gallon. I'd stir it in, and when the temperature in the cooler was 11 degrees warmer than my mash temperature, I'd add the grain.

That worked so well that I lost about 1 degree per hour in the cooler! I still use the cooler MLT when I have a smaller 10 gallon batch, because I liked that part of it so much.

Thank you! This sounds perfect I'll give this a try next weekend!

 

[Yooper]

Thank you! This sounds perfect I'll give this a try next weekend!

Oh, and the reason I don't add ALL of the strike water at first is pretty simple- it seems like since I can only add 180 degree water without warping my cooler that the first addition "sucks" out a ton of heat right away, and then I find that once that happens and it stabilizes that I can add more hotter water and then it will hold that temperature. If you could add boiling water, that would work but then you'd ruin the cooler so I do it in stages.

 

[ron,ar]

I use a 10 gallon Igloo cooler and don't lose too much heat, but I do preheat really good, drain, then add all the strike water. I also cover just to cover the bases.

 

[JohnnySardonic]

I preheat my 13g cooler with my sparge water. When my mash water is about 10 degrees F from strike temp, I start draining the cooler. This way, the cooler absorbs the heat and the sparge water doesn't take as long to heat up the second time. Never lose more than 2 degrees during the mash.

 

[pabloj13]

I just throw a gallon of just-off-the-boil water into my cooler for 10 minutes before mashing in, dumping it just before mash in. Works great.

 

[harry_the_face]

Are you calculating the quantity of water rand the temp based on the grain weight you are using? If not that will make your temps all over the place. I use an android app called brewzor calculator. It does great but a still have to go 1-2 deg higher to get the correct temp

Also keep in mind that heat rises so you will have temp variations from top to bottom of your tun.

I always preheated my cooler with my hot water from the tap (about 130f) until the last 2 batches. I won take the mistake again. Made it much harder to have a consistent temp through to mash.

 

[Polboy]

hym, i take numbers from the beersmith and it just works for me (im at the design mash tem +/- 1-2 deg), after 1h mash im loosing 2-3deg, so the worst case scenario i want 152 mash but after one h i can end up with 147 (but i dont think that ever happened), are you sure your thermometer is ok? and usually i dont preheat (only at coldest days) just put temp of grain and mash tun in beer smith

 

[2thGuy]

I don't preheat my 10 gal cooler and I don't have problems. The 11 degree temp that beer smith generates is just an average, so if your system is consistently 8 degrees below with the 11 degree number, then up your temp of your strike water some. Also, I throw some towels around my cooler and only lose about 1 degree in 90 mins.

 

[jordinio]

Are your batches almost filling the mash tun? i had this problem when i had too much headspace from trying to do smaller batches in the same MT.