Heat and water loss?

I finished making my mash tun with a rubbermaid 12 gallon cooler and tonight I tested how well it would hold the heat at about mash temp (just the manifold in the cooler).

Added 5 gal. "strike water" at 149.5 F
At 36 min. - 144.5 F
At 60 min. - 141.5 F

Is this too much heat loss? I didn't pre-heat the cooler, so I suppose that might make a bit of difference. Also, is there an amount of volume that is acceptable to lose? I figure over the course of an hour I may have lost about 4-6 oz. due to leakage.

I think if you preheat your cooler, you'll find that the temperature loss will be maybe only a degree or two. I preheat mine, let it sit a bit and then put the water back in the kettle for my sparge water. Then add 169 degree mash water, for my mash at 153 (for example). 8 degrees loss is a lot, I think.

Where is your cooler leaking? Mine doesn't leak at all.

The grain will act as insulation as well.
I bought a rubbermaid and found it lost heat during a water test similar to yours - and I later thought about the grain/insulation factor.
Many people on this forum had great results with the rubbermaid brands.
Along with pre-heating, you can also factor in heat loss from transfering the water to the cooler...some heat could be lost by a metal pan and or by splashing.

Did you measure the temp in the cooler as 149.5 - or in the pot on the stove?


Cheers.

It's either leaking inside the washer into the interior of the cooler walls, or from the connecting nut that connects the nipple pipe to the ball lock valve, which I can see water dropping from the connection. I've tried putting teflon tape on the connection, but it still seems to drip a little from some reason. I doubt it's making it into the inner wall of the cooler, as the washer seems to be pretty tight and I think I would lose more volume if that was the case.

I measured the temp once I put it in the cooler, but I think you're right, between pre-heating the cooler and the insulation factor of the grain, I figure that heat loss should be cut in half at least.

I had a similar leakage problem and found I solved it by pulling on the ball valve slightly - this seemed to seal the gap for the most part.
The teflon tape sealed when pulled (or pushed in slightly).


Cheers.

I would also suggest , along with pre-heating the tun, that you heat your strike water a few degrees warmer than your target temp. Let the temp drop to the target before adding the grains. Your Mash Tun should be nice and warm and hold temp better for you.
Edit:
If you your target is 169 heat the water to 172 or 173, add it to your mash tun and let the temp drop to 169.

I have the same cooler and found out after I preheat the cooler for @ 10 minutes before adding the grain, I usually only drop 1 deg in 60 minutes.

I have a 10 gallon Rubbermaid cooler, and a week ago (when I was testing my steam system - see sig), I left 5 gallons of 154 degree F water in it overnight. It had been at 154 for about 30 mins (so well pre-heated), and over the course of the night (about 7 hours) it only dropped 5 degrees. Those coolers really keep in the heat.

Leaks can be fun to track down and stop, I bought the cooler kit from NB for my rubbermaid and ended up not using it, I couldn't get a decent seal. What I finally ended up doing is just sliding a chunk of 1/2 inch high temp hose through the grommet that came with the cooler it works great no leaks and its super simple. As for losing heat I do the preheat with the strike water method, I heat it about 10º F higher than I need and then let it drop down to my strike temp, I never understood why people would put hot water in to preheat then dump it back in the pot and then add the strike water, seems like a wasted step to me.