My 10-gal Rubbermaid MLT -- sucks?

EDIT: Never mind, first mash went fine. RDWHAHB...

I had been mashing in a 9-gal stainless pot, which also doubled as my brewpot. But I got tired of trying to hold the temp in it. It lost heat pretty fast, and while it's possible to add heat, that requires a lot of monitoring, work, and is generally a PITA.

So after reading all the great results people were having with these 10-gal cooler conversions, I took the plunge. Got the cooler for $40 at Home Depot, spent maybe another $20 on the bulkhead and SS braid. After a little trial and error, got it to stop leaking, and decided to test the heat retention. Used the same test I had done with my SS pot: add 5 gallons of 160F water (starting temp measured after the water was n the cooler), put the lid on, hold for an hour indoors at 70F, and measure the temp again.

The results:

5-gal SS pot, no insulation: lost 8-9 degrees
5-gal SS pot, with homemade insulation blanket: lost 3-4 degrees
New Rubbermaid 10-gal cooler MLT: lost 7-8 degrees

That's right, not much better than the plain old SS pot. That's with no stirring, no removing the lid...nothing. And I've done the test twice, with three different thermometers.

What the heck is going on here? I think the test was a pretty reasonable facsimile of mash conditions (adding grain wouldn't change the thermodynamics all that much...the 5 gal I used was about the same heat capacity as a 14# mash). Just out of curiosity, I ran the test using 3 gallons of water (roughly the same heat as a 9#mash) and lost even more ...9-10 degrees.

Could all the extra airspace at the head of the 10-gal cooler have something to do with this?

Is it possible that the Rubbermaid coolers at Home Depot are spec'd lower, and that's why they're cheaper?

Anyone else using one of these coolers see anything like this?

At this point, I'm wishing I'd saved the $60 (not to mention the time) and put it towards a keggle

 

Did you pre heat your cooler, I take at least half the volume of the mash tun and pre heat that amount of water to about 170 let it sit for about 10 min and emty.
Then I mash in. Coolers in general work great.

 

I used my Rubbermaid 10 gallon MLT this weekend for the first time and I list 2 degrees over1.5 hours. I also have through the wall digital therms too so that I could monitor the temps. I opened it up every 10 minutes too, to stir the mash...

 

My 10 gal MLT went from 162 to 158 over 90 minutes on a 30 degree day. I'll take it.

 

I use a 10 gal gott cooler and preheat with 2 gals of 155 deg water for @ 10 min and usually only drop 1 deg in 60 min.
I use a Type-K thermocouple and can keep my lid closed tight and it gives me a digital readout on my ohm meter.

Make sure you keep the lid on and preheat first.

 

Couple of comments.
With a pot when you add hot water the temp of the pot quickly stabilizes to the temp of the water. The cooler will take longer to stabilize so your starting temp will take a little longer to reach. It might also drop your initial infusion a little more before stabilization than a pot. Measure the water temp after 5min then measure the temp loss from there for a good idea how well a cooler works.

Second the thermodynamics are not the same with water as with a mash. A mash is thick enough to stop any convection currents while plain water will have convection currents that transfer heat to the top and outside surfaces. However I think this would affect the pot moreso than the cooler.

Craig

 

Thanks all for the thoughts...

I don't think it's a preheat issue, as the "start" temp wasn't taken until after about 5 min in the cooler (it had dropped ~3 degrees from the temp in the pot).

And it doesn't have anything to do with opening, stirring, etc., because I didn't.

I like the convection current idea... I was trying to think of a plausible reason why plain water vs. a mash would give different results, and that sounds pretty good. But, as CBBaron said; I'd still expect the cooler to outperform an uninsulated stainless pot by more than a couple degrees.

Anyway, I was going to try this out on my next batch tonight...but it's a 20#-mash, and I'm not sure I want to risk it. Maybe I'll RDWHAHB, and it will all become clear.

 

Dude, a 20# MASH in a 10 gallon cooler will probably lose next to nothing... that is ALOT of thermal mass in there!

Pol

 

Soooo right. Brewed this last night. Heated 6.25 gal water to 170F, transferred it to the cooler, put the lid on and waited 10 min. Water stable at 166. Stirred in the 20# grain bill. Temp stable at 152F. 75 minutes of mashing later, sith two stirrings in between....151F.

Efficiency not great (63%), but that had nothing to do with the cooler. Couldn't batch sparge (too big), couldn't mash out without taking the mash out of the cooler and heating it, went a little too slow with the fly sparge so the grain bed was a little cool. Whatever. Boiled off a little more than I anticipated, so I only missed my OG by 5 points.

As a side, this brew is shaping up to be AWESOME. I'm really liking the Centennial/Willamette combo...smells really rich. The aroma is so strong in the primary, I may skip the dry hop. Used my new oxygen stone, pitched onto a yeast cake, and the airlock started bubbling IMMEDIATELY. (Course, what was I thinking with the airlock? Even at 5 gal in a 7.5 carboy, the airlock blew off in 4 hours. Minimal damage -- I was standing right there -- and blowoff tube safely installed)

Oh, and I put my hop rhizomes in the ground today. So it's been an awesome 12 hours

RDWHAHB

 

While the insulated cooler is obviously better than any metal will be at holding your temp, SS is a pretty ****ty conductor of heat. Just something to think about.

 

Heat wants to transfer somewhere. No grains and the only place for the heat to transfer is the outer walls.

Add your grain bill and you've just added a sh!t load of surface volume that will be glad to take that heat transfer. Those grains make all the difference in whether the heat goes or stays.

 

My Hugh Heffe from last weekend was 10lbs grain in a 10 gallon cooler. I lost 1 - 2 degrees over an hour. Not bad, stirred a few times. Mashed out with an infusion of water and got er up to 165 F.... 80% eff during my first brew session with this system.