Cooler Mash Tun Temp Drop

[FatherJack]

Hey all,

I'm two batches in on my all grain experience and I've noticed I have a consistent temp drop in my two batches. Please forgive me if there are answers on the forum, I checked and couldn't find anything quite like this:

I preheat my mash tun using water that's about 140 from my tap and then adding about 14 liters of water that's about 180 degrees. I let this sit for about 10 minutes and then start slowly draining the water. When it's nearly empty, I dump it out, add my grains and then add my strike water.

I have no problem hitting my target temps. My last brew I was shooting for 153 and I hit 155. I figured this was close enough and sealed the deal.

I watched the temps over the course of the hour and I ended up with 149. My first AG batch started at 154 and ended at 148. Is this normal?

I have two plausible theories:

I think I might be losing temperatures from the drain valve, but I'm not sure if it could be this much. I use PVC piping and a plastic valve to regulate the flow. I am thinking to maybe wrap some (clean) winter style socks.

The other possibility is my thermometer is lying. It's not the greatest thermometer and I suspect it's lying to me, especially when sitting for an hour. I was shooting for 1.056 on my last batch and hit 1.050 So I'm not entirely sure it's this...

Thanks for the help!

(Also, I left the grains in the tun during the brew process, took a nap after all was done, ate dinner, cleaned up my mess and finally got to making cookies 8 hours after I was done with the grains. I opened up the cooler and the grains were still steaming. It seems well insulated enough...I dunno...)

 

[trigger]

Couple Q's:

1) What brand, type, and size cooler? Model number would be great!

2) What brand and type of thermometer? Model number would also be great!

Can you take and post a picture of your setup?

 

[FatherJack]

Trigger,

Many thanks!

The cooler is an Igloo MaxCold 50qt. Here's two pics:

https://cdn.homebrewtalk.com/gallery/showphoto.php?photo=44106&title=p1020695&cat=500

https://cdn.homebrewtalk.com/gallery/showphoto.php?photo=44107&title=p1020696&cat=500

The thermometer is a TruTemp 3518N

 

[trigger]

I used a very similar cooler before my current setup. The lid was hollow, and that was the most significant source of heat loss on cold days. When the weather was warm, like 20 C, I would only loose about 1 deg. When it was cold I found that folding a beach towel up, then placing it on top of the cooler made a huge difference. Maybe give that a try. You could try cutting a hole in the top and filling it with sprayfoam, but I'm not sure how effective that would be.

I highly doubt that your valve setup is the most significant source of heat loss. It's too small a volume in there.

You may also be experiencing some thermometer errors if you're using s digital thermometer. What type are you using? Do you have a second thermometer (dial or glass) that you can use to verify the temps?

 

[AussieBrewerInColorado]

Try adding 180 degree water to your cooler and waiting till it settles to about 168. Add your grain then, and it should be in temp ranges for your brew. When I first used a cooler I added water to grain and the temp was off. Ever since, I add grain to water (contrary to John Palmers book).

 

[AussieBrewerInColorado]

Agree with Triger, use a few different thermometers and average for the right temp. I use a digital cooking thermometer to check temps but have a floating thermometer to confirn,

 

[AussieBrewerInColorado]

BTW, in my opinion start a few degrees higher and you'll end up in the 150 range after mashing, which is where you want to be. (for most brews).

 

[FatherJack]

Thanks! I forgot to write it, but for the last one, I put a blanket on top of the cooler too. Even with the blanket it still declined at about the same rate. I think in the first 20 minutes I went from 155 to 154. Then in the next 20 minutes it went from 154 to 152. Then the last 20 it went down to 148. Seems a little strange to me...

Something tells me it may be my thermomomememeter and maybe my missed OG was due to being a AG noob and not temps...

Also, from now on, I'll add the grains to the water and see if that helps.

 

[nebben]

Your mash can also get cooler/warmer spots too. When taking temperature measurements, stir it up a little bit to get a consistent measurement. Different thermometers frequently disagree too. YMMV.

 

[BendBrewer]

Did you by any chance get your ingredients from a guy that flew back to Oregon after the quake? I met a guy last week that was picking up supplies for his buddy in Japan.

I use a 10 gallon cooler as well. I just use a thick towel on the top of it. Brewed last weekend in 40 degree weather and lost 2 degrees over the hour.

 

[smizak]

My cooler-tun will do the same. I open it every 15 minutes or so and take a couple quart mini-decoction out. About 2 quarts heated to boiling in my system will bring it up one degree. My first all-grain beer fermented down to 1.008 and I couldn't figure out why with a 154F mash temp. Then I started checking subsequent brews. It's a PITA, can't wait to get a RIMS/HERMS going, but it's the only thing I can do to maintain a stable mash temp.

 

[Scooby_Brew]

My cooler did the same when I left it in a cold garage. Now I keep it in the warmest spot in my basement, pre-heat it with some boiling water, keep a blanket over it, and in the middle of the mash I add some boiling water and stir like hell for 5 min for higher efficiency. Now I end up with 2-3 degrees higher temp at the end. So for an APA I like to start at 150 and finish at 152-3. My efficiency jumped by a 4-5 points also.

 

[payton34]

i have an igloo 50 qt cooler. i float a peice of foil faced styrofoam insulation that i cut to size and i don't lose any temp at all even in winter. the styrofoam is key because the cooler lid has no insulation. it also means no airspace from top of mash to top of cooler

 

[RichBenn]

I always keep the cooler closed while pre-heating. Depending upon the ambient temperature, you may have to start at quite a bit higher temp and give it some time to equalize. There is alot of thermal mass in the cooler, and you don't want to be contributing to warming the thing up during the first 10 minutes of mashing. That's one potential problem.

The second potential problem is stirring. First few times I mashed, I kept noticing different readings in different locations. You need to stir alot. I now strike a couple of degrees higher than I used to, to account for the lid being open more and me stirring more. I check the temps all around, and eventually they get closer.

The third potential problem is the lid. Is it open alot? Heat rises, so opening loses heat. Once you get the long enough preheat, strike, and stirring process down so you start with the right temp, keep the thing closed with no opening the lid to check. Put a think towel over the whole thing.

And if you drop just 2 degrees, well done, RDWHAHB!
Whenever you open, they'll be all this steam up on the lid, which serves as an evaporative cooler in addition to the mash getting a little evap cooling. If you just lift a little to check temp, maybe not such a big deal. But you can easily add a few degrees temperature drop if you are opening all the time.

 

[Scooby_Brew]

i have an igloo 50 qt cooler. i float a peice of foil faced styrofoam insulation that i cut to size and i don't lose any temp at all even in winter. the styrofoam is key because the cooler lid has no insulation. it also means no airspace from top of mash to top of cooler

That's a great idea! :rockin:
But is the foil faced styrofoam food safe?

 

[RedHouse]

I have a 48 qt coleman cooler that I use. I was losing about 4-5° over the course of an hour too. I got a can of spray foam, drilled a few ¼" holes in the lid, filled it with spray foam. I just did a 90 min mash this Sunday, and only lost 1°.

I also preheat with 180°, let it sit for ten minutes or so, then open the lid and let the temp drop to about 168°...then add my grains, stir, close lid and wait.

 

[FatherJack]

Did you by any chance get your ingredients from a guy that flew back to Oregon after the quake? I met a guy last week that was picking up supplies for his buddy in Japan.

I use a 10 gallon cooler as well. I just use a thick towel on the top of it. Brewed last weekend in 40 degree weather and lost 2 degrees over the hour.

That sounds like my buddy in Tokyo. He usually orders from AHBS and has a re-shipper send it to Japan. This time customs said no way man, you can either mail it back, you pay for it, or you can keep it, but you need to test each item at $70 (and he had like 30 items) or you can throw it away and you still need to test each item.


I heard about all this and said to myself, not worth it. On my last trip back to the states I picked up some necessaries such as copper tubing, my cooler, some hops and some yeast and brought them back.

Now I order my grains from a guy in Tokyo. I pay a little more, but I don't have to deal with that headache.

 

[FatherJack]

There's a lot of great ideas on this thread. Thank you for all the great responses everyone! I'm gonna bookmark this thread and make some changes for my next brew.

Thank you so much again!

 

[cjb]

I have a 48qt Ice Cube cooler, and on my batch yesterday I lost 6deg over the course of an hour (154 -> 148F). This was with a sleeping bag bungied over the cooler.

I like the idea of the floating styrofoam false lid...anyone else tried this?

 

[Bobby_M]

You have to preheat with water over your desired mash temp and it's also a good idea to tilt the cooler so that the water touches each wall nearly up to the top. These colder areas become a heat sink over the course of the mash.

 

[michaeltrego]

I have a 48 qt coleman cooler that I use. I was losing about 4-5° over the course of an hour too. I got a can of spray foam, drilled a few ¼" holes in the lid, filled it with spray foam. I just did a 90 min mash this Sunday, and only lost 1°.

I also preheat with 180°, let it sit for ten minutes or so, then open the lid and let the temp drop to about 168°...then add my grains, stir, close lid and wait.

+1...same here...insulated my lid with great stuff foam, and preheat the tun with hot tap water (tilt it around a few times to cover all sides) while the strike water is heating. With that I only lose about 1 degree during the course of the mash.

I also use a thermometer with a long flexible wire lead (waterproofed with Bobby_M's method) so I can close the lid tight on it. This eliminates the need to open the lid to check the temp during the mash, and thus no additional heat loss.