Rubbermaid Cooler Heat Loss

I've been having some efficiency issues lately, went through all the steps (adjusted the mill with feeler gaugues, made sure all my water volumes were spot on in Beersmith, etc) so I did one more experiment. Pre-heated my tun, the old orange rubbermaid cooler, and filled it with water. Started at 153.6F, and 70 minutes later was at 146.2F. That's 7.4F loss in 70 minutes, what gives?! I know a lot of people use these, did I get a dud or something? Can I attribute poor mash temp stability to trouble with efficiencies?

 

5gal or 10gal cooler? I have both, and the 5gal doesn't hold temps as well as the 10gal (less thermal mass). I also improved things by filling the lid full of "Great Stuff" crack sealer foam. My losses range from 7 degrees an hour (5gal, hollow lid) to hardly any loss (<1*) over a 60 minute mash (10gal, filled lid).

 

How did you fill the lid? Any instructions?

 

I filled the lid today, pretty simple. Just drill a few small holes around the top of the lid, take the applicator on a can of Great Stuff (Any hardware store has it) and jam it in each hole and fill. It will expand like crazy inside (and also bubble out the holes, so plan for that), and insulate the lid. Hopefully this will help my temp issues.

 

Have you made a foam board "float" to go on top of your mash? That works wonders.

 

Let us know if that foam ever actually cures...

Cheers!

 

I never lose a full degree with my 10 gal rubbermaid tun....usually around 1/2 degree!

 

I have a 10 gal Rubbermaid that I drilled the lid and installed a bulkhead for my thermometer (hate it getting in the way when I stir).

I only lose 1/2 a degree F over the course of an hour, if that.

 

+1 on the foam board. I have the 10g Home Depot cooler and had the same problems loosing heat on 5 gallon batches. After adding the foam plate to the top of the mash and insulating the lid, my temps are spot on.

 

what is this foam board? Im inteested in doing that combination to mine as well

 

Please post some pics of this foam board.

 

Take some 2" thick pink insulating foam and cut out a circle the diameter of the inside of your mash tun. When your done mashing in place the foam circle directly on top of the mash to help insulate it.

 

It's technically extruded or expanded polystyrene board. The pink kind is Foamular F-150 by Owens Corning at Home Depot. Lowes has another brand. It only comes in 4x8 sheets though and the 2" thick is about $25. I had some extra 1/2" from another project, so I just cut a couple circles and doubled it up. Be sure to clean it well, or it will grow funky stuff. Maybe a good reason to have extra around.

 

You might not be be preheating sufficiently. I usually just make my strike water about 8 degrees warmer and let the water sit in the cooler for about 10 minutes before I dough in

 

I don't know about you but I don't want any pink stuff or styrofoam stuff floating in my wort for the sake of a couple degrees. Talk about overkill.

 

Think I read in another thread that the foam will fit in a slow cooker liner that you can pick up in the grocery store (near the tin foil and plastic bags).

 

I wrap the float with multiple layers of saran wrap. When I'm done, I just remove and pitch the wrap.

And, a "couple of degrees" makes a LARGE difference when mashing.

 

Woa fellas...time out here! The OP tested his MT with just hot water only. A mash will behave much differently and hold heat much better than water. The original experiment is invalid IMHO.

We got a witch hunt goin here...

 

This would also be my guess.