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Brewing At 2 Temps In 1 Fridge

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Ross

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I have a single fridge that holds 2 fermenters & I'm currently brewing an Alt at 15c & a bitter at 19c at the same time. I have the temp probe sat in the alt & added the bitter at 19c. They have been going for 3 days now & are still sat at 4c difference. i'm wondering whether it would be possible to brew a lager at 10c & an ale at 18c using this method - has anyone ever tried it?
 

kungy

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How the heck does this work? How can they hold two seperate temps in the same fridge. Is it different temp zones??

Will
 

Ross

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kungy said:
How the heck does this work? How can they hold two seperate temps in the same fridge. Is it different temp zones??

Will
[post="57868"][/post]​
No, just 2 fermenters in a normal fridge - The thermostat temp probe (controls temp to +/- 0.5c) is fully immersed in one of the brews & both being of equal volume, whatever temp change happens to one brew, happens to the other also - I noticed this on my last 2 brews which i wanted to brew at the same temp, but whichever fermenter I controlled the other stayed 2c out. the only way to get back in unison was to take the cooler one out until it reached the same temp & then back in the fridge.
So tried it this time deliberately with a 4c difference & its working great - thought in time they might come together - so I guess what I'm asking is, will the fridge in cooling mode cool the 18c brew at a different rate than the 10c brew if both are of equal volume?
 

NRB

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Ross said:
No, just 2 fermenters in a normal fridge - The thermostat temp probe (controls temp to +/- 0.5c) is fully immersed in one of the brews & both being of equal volume, whatever temp change happens to one brew, happens to the other also - I noticed this on my last 2 brews which i wanted to brew at the same temp, but whichever fermenter I controlled the other stayed 2c out. the only way to get back in unison was to take the cooler one out until it reached the same temp & then back in the fridge.
So tried it this time deliberately with a 4c difference & its working great - thought in time they might come together - so I guess what I'm asking is, will the fridge in cooling mode cool the 18c brew at a different rate than the 10c brew if both are of equal volume
From a thermodynamic point of view, both fermenters should achieve the same temperature over time. They will both equal ambient fridge temp. What were you measuring temperature of each fermenter with?

An interesting theory nevertheless.
 

Wortgames

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Ancient chinese brewing proverb (maybe):

"Brewer with 2 thermometers never know what the temperature is".

Firstly, I have measured the temps in a couple of my fridges extensively, and there can be up to 4 or 5 degrees difference between different parts of the same fridge at the same time.

Usually the top part is the coldest, but when the compressor has been off for a while the air can stratify and it will become colder at the bottom. It is also not as simple as higher or lower, there are all sorts of slow convection dynamics that create 'channels' of cold air in certain places.

Because a fermenter full of beer has quite a large thermal mass, my theory is that if your fridge is within a couple of degrees of the fermenter temp, it really won't have much effect on it. Therefore the fermenter will stay largely at its initial temp. Once the yeast have finished and over time, the two fermenters will equalize at the average fridge temp, but theoretically if one was on the top shelf and one was on the bottom they may remain a couple of degrees out for all eternity.

So I hate to burst anyone's scientific bubble, but any thermometer or probe will only tell you what the temperature is at that specific point - kind of like looking at one pixel of a picture and surmizing 'this picture is green'.

So to answer Ross's question, I'd say that yes it would be very possible in theory - what you'd need to do is put a fan or two inside the fridge to keep the air turbulent, and try to maintain a constant 14C (half way between your two targets).

Remember that different yeasts will generate different amounts of heat though...
 

PeterS

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Wortgames said:
Ancient chinese brewing proverb (maybe):

"Brewer with 2 thermometers never know what the temperature is".


So I hate to burst anyone's scientific bubble, but any thermometer or probe will only tell you what the temperature is at that specific point - kind of like looking at one pixel of a picture and surmizing 'this picture is green'.

So to answer Ross's question, I'd say that yes it would be very possible in theory - what you'd need to do is put a fan or two inside the fridge to keep the air turbulent, and try to maintain a constant 14C (half way between your two targets).

Remember that different yeasts will generate different amounts of heat though...
[post="57895"][/post]​
I believe this would be the best explanation I heard to date. In my case, I was wondering about my rather small Fridgedaire that I use for fermenting. This fridge has a channell from the top freezer section that is connected to the rest of the fridge. Whilst both sections can be controlled by a switch, I found that unless I have the freezer on full, the control in the fridge will not alter very much. In deed, it was probably manufactured to have a varient temp relaying on thermal currents or whatever, without the ability to vary the temp very much. Now that I use an external controller, I find that it takes relatively short time to get the temp to where I set it, but that temp is only at that presise location. A thermometer placed at a higher shelf than the probe for the external controller will be out as much as 4-5 degree. Even if you place a probe in the top, middle or bottom of a fermenter, probably will show different readings, depending on thermal mass or how long that mass has been subjected to a constant temperature, therefore a slow change overall. Averaging seems to be our only choice..

Chees,
Keep on Brewin' :beer:
 

Ross

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both fermenters are permanently monitored by probes inside the beer - i've tried switching the fermenters over to see what effect this has & it makes no difference, so it's not because 1 areas cooler than another. Whatever the reason is, it's allowing me to brew at 2 different temps which is pretty useful. i will try to do a lager at the same time as an ale when my lager fridge is available as back up incase it doesn't work at the bigger temp difference - i'll post the results....
 

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