Cooler temp loss 8-12F per hour normal?

[Nemanach]

I just went back to all grain brewing and have been measuring the temp loss on my mash tun. I have a 48 quart Coleman cooler in the pictures below.

My last batch was a Cream Ale. I had 8 lbs of grain and 2.5 gallons of strike water. I was mashing at 150F and measured a 8 degrees F loss over an hour. Ambient temps were 75 degrees that day.

Today I am working on a Berliner Wiess doing decoction mashing. During a 45 minute wait at 146F I say a 9 degrees F loss, this would be 12 degrees over an hour. This batch had 7.3 lbs of grain and 2.28 gallons of strike water. Ambient temps are 80 degrees today.

Does this make sense? It could be that my thermometer is wonky but it seems to read boiling fine.

 

[mongoose33]

I have never not insulated my mash tun (similar cooler). Even in much colder temps than yours I rarely have more than a couple degrees loss over an hour. I also always pre-heat the cooler with a gallon of boiling water. Dump it in, let it sit for 20 minutes or so.

Get a blanket or sleeping bag or something like that to wrap around and over it. If you have wind it's essentially producing a wind-chill effect on the cooler and if it's sitting outside on the deck you may have that as well.

The other part of your problem is that there's not a lot of thermal mass there. I typically have about 10-12 pounds of grain and 4-4.25 gallons of water in my mash tun. The smaller your batch size the more heat the cooler will pull out of it, relative to its size.

 

[Shepbrew]

Agree on the thermal mass being an issue. I use the same cooler with no extra insulation and have at most 1f loss per hour, but do about 10-12 lbs plus about 8 gallons of water so it's real full. This is now that I usually do no sparge, before when I was batch sparging I would lose more heat.

 

[day_trippr]

To the OP: do you pre-heat your MLT before dough-in, or if not, do you use a mash calculator to determine the optimal strike water temperature to account for heating up the tun plus the grain and ending up at mash temperature?

When I was using a 10g Rubbermaid, BeerSmith2 reliably calculated the strike water temperature needed to hit the desired mash temperature given the tun temp (taken with an IR gun) and the grain temp (taken with a Thermopen buried to half-depth). Heat loss was a non-issue...

Cheers!

 

[jwelch1103]

IMO, its that model cooler. Not all coolers are created equal and I have/had two identical Coleman coolers. Preheating and additional insulation, as has been mentioned, will help.

I mash in Igloo marine coolers, either a 72 quart or 128 quart depending on the grain bill. The Igloos require no additional insulation and hold temp very well.

Coleman does make better insulated coolers. I'm not saying you need an Igloo, you just need more/better insulation.

 

[Revvy]

I was just going to say the same thing as Day Tripper. Preheat Mash Tun, take temp of grain and tun (all I do to preheat my cooler is fill it with a couple gallons of hot tap water and close it up and give it a couple swirls and let it sit til you need it. Then factor those numbers into brew software when calculate strike water temps.

 

[Nemanach]

Thanks for the input. I'll do some research on no sparge brewing for these smaller beers. Next weekend I'm doing a 10g batch that requires 24 lbs of grain so that should determine if it helps. I use a calculator with a cooler weight of a little more than 9 lbs and a specific heat of .3. Currently I'm using the Beer Cipher excel sheets but I have checked it against beersmith and both agree on mash in temps.

 

[devils4ever]

I had similar issues with heat loss in my cooler. That's why I switched to mashing and sparging in big SS pots. You can add heat when needed. Now, I have a HERMS system and can maintain any temperature I want to within 1 degree. Plus, you can do a step mash.

 

[markcurry]

I've got the exact same cooler. Matter of fact from the picture, I'd say the exact same setup. If I'd seen your picture out-of-context, I'd say you stole my tun!

In any event, I rarely loose more than a degree or 2. Insulate the tun with blankets/etc, preheat it, and don't stir excessively. Let 'er ride with the top closed. Only on the coldest days do I get 3-4 degree drop in an hour.

Regards,

Mark

 

[Nemanach]

Do most people preheat and assume no loss to cooler or anticipate a loss and start with an ambient temp cooler?

 

[wilserbrewer]

A few ways to go about it, the easiest way imo is to add sparge water 10 degrees hot and allow it to come to strike temp while preheating the cooler

 

[V-Fib]

I have the same cooler that I converted. I had to put a ratchet strap around it near the top because the lid had about a 3/16" gap that would spew steam out of it. I also put 3 layers of foil over my mash after I dough in. Since then I lose maybe a degree over an hour with stirring 2 more times.

 

[Shepbrew]

Do most people preheat and assume no loss to cooler or anticipate a loss and start with an ambient temp cooler?

I will preheat on a very cold windy winter brew day, other than that have not found it necessary.

 

[mongoose33]

I will preheat on a very cold windy winter brew day, other than that have not found it necessary.

I think there's simply a learning curve to what works. I'm in Wisconsin, gets cold here (Ontario? Same).

Once I was getting stuff ready the night before, crushed the grain, set up the kettle in the garage, like that. Left the crushed grain sit out there in a covered bucket overnight. Followed my normal pre-heat-the-mash-tun approach, only to find I missed my mash temp by several degrees low.

Why? The garage was probably 45 degrees, the grain equalized to that temp, and sucked more heat out of the water than I had planned for. Now, when I crush the night before I keep that bucket in the house so it can't drop below about 68 degrees in the winter.

Live and learn.