Author Topic: Cooler not holding temp well - Losing more than 15 degrees an hour  (Read 1315 times)

Offline Phil_M

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Finally managed to get a decent brew day on the books. Irish red for St. Patricks day, turned out 10 points lower than expected but I really don't mind that. (1.032 OG, boil off was way low. Was supposed to be 1.042.)

What I do mind is my mash tun. I've been having issues with lower than expected mash temps, and upped the ante on how I measure temps for this brew...and I lost a whopping 16 degrees. Weather was upper 40's, no wind.

The cooler was about half full. I bought this size cooler with the intent of brewing 10 gallon batches for lower gravity beers, and 5 gallon batches for higher gravity beers. Currently the water supply for my counterflow chiller is not available, so I've been brewing 5 gallon batches so the brew kettle can be carried into the kitchen. There I can use my immersion chiller hooked up to the kitchen faucet.

So did I lose all my heat because the cooler wasn't full enough? I'm honestly not sure that's all it is...temps fell from 156 to 140 in about 50 minutes.
« Last Edit: February 27, 2017, 09:46:47 PM by Phil_M »
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline Stevie

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Cooler not holding temp well
« Reply #1 on: February 27, 2017, 02:44:15 PM »
Shouldn't drop that much. Do you pre heat? Have you measured 10 minutes in to see where it's at? I have brewed in <32° temps and lost only a couple degrees.

ETA - if you don't pre-heat, do you account for the temp loss caused by the cooker being cold?
« Last Edit: February 27, 2017, 02:57:49 PM by Stevie »

Offline HoosierBrew

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Re: Cooler not holding temp well
« Reply #2 on: February 27, 2017, 02:54:12 PM »
Shouldn't drop that much. Do you pre heat? Have you measured 10 minutes in to see where it's at? I have brewed in <32° temps and lost only a couple degrees.


I agree. I only lose a degree or two. Is your thermometer reliable, Phil?
Jon H.

Offline Phil_M

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Re: Cooler not holding temp well
« Reply #3 on: February 27, 2017, 03:53:51 PM »
Thermapen MK4, that gets used daily and checked against ice water fairly often. Well, less often now, it's never budged.

I don't pre-heat, but the cooler/grains were stored inside until right before I added strike water/doughed in.

Only thing I can think of is the lid is somehow no longer seating properly.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline HoosierBrew

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Re: Cooler not holding temp well
« Reply #4 on: February 27, 2017, 03:58:44 PM »
Thermapen MK4, that gets used daily and checked against ice water fairly often. Well, less often now, it's never budged.

I don't pre-heat, but the cooler/grains were stored inside until right before I added strike water/doughed in.

Only thing I can think of is the lid is somehow no longer seating properly.


FWIW, I cover my cooler with a blanket or sleeping bag, and the put a dumbell weight on the lid. I'm still puzzled at such a high temp loss though, even if the lid doesn't seal perfectly.
Jon H.

Offline Phil_M

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Re: Cooler not holding temp well
« Reply #5 on: February 27, 2017, 04:14:29 PM »
I'm wondering now if wort has made it into the insulation and has caused it to deteriorate. The cooler is setup similar to how Denny's does his, just with a different sort of bulkhead through the cooler.

If the insulation is deteriorating it'd explain why this issues seems to be getting progressively worse.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline Philbrew

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Re: Cooler not holding temp well
« Reply #6 on: February 27, 2017, 05:33:51 PM »
I'm wondering now if wort has made it into the insulation and has caused it to deteriorate. The cooler is setup similar to how Denny's does his, just with a different sort of bulkhead through the cooler.

If the insulation is deteriorating it'd explain why this issues seems to be getting progressively worse.
Have you ever weighed it empty?  If it has gained weight that would indicate wort in the insulation.
Many of us would be on a strict liquid diet if it weren't for pretzels.

Offline Phil_M

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Re: Cooler not holding temp well
« Reply #7 on: February 27, 2017, 05:46:14 PM »
I didn't, kinda wishing I had. Guess I could guestimate it by comparing it with a new cooler at the hardware store...
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline Phil_M

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Re: Cooler not holding temp well - Losing more than 15 degrees an hour
« Reply #8 on: February 27, 2017, 09:49:35 PM »
Talked to several homebrewers at work, they're equally stumped. Has to be something with the insulation, these rates almost suggest mashing without a lid.

I'm kinda pissed, was hoping to limp this mash tun along till we could move out of the condo and into a house.

This brewday was also a try to see how my system help up to a low oxygen mash...and it failed miserably. So I'm already considering moving on from this cooler.

Still pissed though.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline Andor

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Re: Cooler not holding temp well
« Reply #9 on: February 28, 2017, 05:02:30 AM »
Thermapen MK4, that gets used daily and checked against ice water fairly often. Well, less often now, it's never budged.

I don't pre-heat, but the cooler/grains were stored inside until right before I added strike water/doughed in.

Only thing I can think of is the lid is somehow no longer seating properly.


Pre heat your cooler, I bet that's the problem. Add water 10-20 degrees hotter than you strike temp shut the lid and wait a few minutes. Open the lid and recheck temp. The cooler will absorb a decent amount of heat right off the bat, which is likely most of the loss in temp you are seeing.

Offline Phil_M

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Re: Cooler not holding temp well - Losing more than 15 degrees an hour
« Reply #10 on: February 28, 2017, 11:32:17 AM »
Pre heat your cooler, I bet that's the problem. Add water 10-20 degrees hotter than you strike temp shut the lid and wait a few minutes. Open the lid and recheck temp. The cooler will absorb a decent amount of heat right off the bat, which is likely most of the loss in temp you are seeing.

But why the change in that shift? Brewing is all about repeatability, and this tun has been anything but. The cooler is always stored inside, at about the same temp (plus or minus 2oish).

And I hit my starting temp, after a few minutes (once all dough balls were broken up/everything was mixed in)the temps in the cooler were between 154-156o, depending on where I took the reading. If I wasn't using water that was hot enough to bring the cooler and everything else up to temp I'd never had hit my temp to begin with.

Dough-in took longer than normal on this beer, I was glad I purposefully overshot my strike temp.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline bayareabrewer

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Re: Cooler not holding temp well
« Reply #11 on: February 28, 2017, 05:23:29 PM »
Thermapen MK4, that gets used daily and checked against ice water fairly often. Well, less often now, it's never budged.

I don't pre-heat, but the cooler/grains were stored inside until right before I added strike water/doughed in.

Only thing I can think of is the lid is somehow no longer seating properly.


Pre heat your cooler, I bet that's the problem. Add water 10-20 degrees hotter than you strike temp shut the lid and wait a few minutes. Open the lid and recheck temp. The cooler will absorb a decent amount of heat right off the bat, which is likely most of the loss in temp you are seeing.

gotta disagree. He's losing temp over the ocurse of the mash, not the initial dough in. I'd echo everyone elses sentiment and say the insulation is shot. you can get a new cooler cheap at wal mart, or I see them all the time at garage sales.

Offline Philbrew

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Re: Cooler not holding temp well - Losing more than 15 degrees an hour
« Reply #12 on: February 28, 2017, 05:28:42 PM »
Crazy thought...drill a small hole into the insulation near the bottom and see if anything leaks out.  You might need to drill one near the top too.
Also check if the insulation that comes out with the drill is damp.
Many of us would be on a strict liquid diet if it weren't for pretzels.

Offline bayareabrewer

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Re: Cooler not holding temp well - Losing more than 15 degrees an hour
« Reply #13 on: February 28, 2017, 05:32:44 PM »
Crazy thought...drill a small hole into the insulation near the bottom and see if anything leaks out.  You might need to drill one near the top too.
Also check if the insulation that comes out with the drill is damp.

post pics if you do.

Offline Philbrew

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Re: Cooler not holding temp well - Losing more than 15 degrees an hour
« Reply #14 on: February 28, 2017, 05:33:10 PM »
Another thought...fill the tun with REALLY hot water and wait a few minutes.  Feel it all over for hot spots.
Many of us would be on a strict liquid diet if it weren't for pretzels.