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Brew Fridge v Freezer


Titan

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Wondering about contol of temperature. I have a freezer. Finding that these promote a swing in temperature + minus 2 deg. Pretty sure a fridge with a more gentle cooling cycle would be more suitable. Thoughts on this who use 1 or both units.

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I'm running a split fridge freezer atm for fermentation and I prefer to use the freezer section when possible. I find it holds temp better and seems to have to run less throughout the brew. When it does run it doesn't take as long to get back to temp. 

Lately I've been doing double batches in the fridge section but will be doing a single batch of pilsner next and will definitely use the freezer for it.

It also gives me ample room for lagering and beer storage in the fridge section when I use the freezer for brews. I have homemade ply shelving that just slide in or out easy enough. 

I'd rather a decent sized chesty anyday but for now the 'hard-rubbish' fridge lives on 🤘

Cheers, Lee

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I only use a freezer so cannot compare to a fridge.  Initially I get a bit of fluctuation.  Say, when I put a 20° fermenter into the freezer set at 11.5° with a 0.5° kick in temperature difference.  Freezer works its guts out to get the fermenter down to 11.5°.  It stops when the reading gets to that temperature, but due to cooling the surrounding air temperature even further, the probe reports a drop below 11.5°.  It might go as low as 8°.  The wort absorbs that temperature much slower though so is not down to 8° itself.

I find that this variation has settled down within 24 hours and like Otto says, it does not vary by more than 0.1-0.2° from the set temperatures.

When it does kick-in, I imagine that a freezer can bring the temperature down much quicker, so runs for less time and is probably a better insulator too.

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5 hours ago, Otto Von Blotto said:

How are you measuring the temp? If the probe is taped to the fermenter underneath foam or whatever then the reading is very close to the actual wort temp. 

Agreed, I've been doing this on my brew and the temp seems to be very accurate. Also stops the fridge turning on every time you open the door to check the brew.

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I sandwich the probe between the base of the fermenter and the board it sits on.  Not taped and not under foam.

Now, before someone goes off-tap about not being taped under foam and not best practice hear me out.

If I did tape it under foam it would be close to the temperature of the wort. Say 20 degrees to start with.  The freezer would kick-in and run until the sensor detected 11.5 degrees, essentially until the wort was at that temperature.  To get to there the freezer would have been running constantly for ages (maybe not so good for the compressor) and the ambient air temperature in the freezer would be well below zero.  Then the freezer turns off.  Then the 11.5 degree wort and the minus 5 degree ambient air try to reach an equilibrium.  Therefore the wort temperature continues to drop.  It is then up to the air surrounding the freezer to eventually warm the wort and the probe inside of the freezer, through its own insulation and the foam enough to warrant turning on the freezer again.   By this time the wort may have got down to say 5 degrees for maybe a day.

The way I do it allows the wort temperature to gradually drop to 11.5 degrees and I have found this equilibrium is reached in under a day.

Plus gives the wort a warmer start to encourage yeast growth.  Which corresponds to some advice to start lagers around 20 degrees then drop to 12 after about 12 hours.

Cheers Shamus

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I doubt it would harm the compressor, as the freezer would simply be running as normal until the probe detected the set temperature i.e. turning the compressor on and off at intervals as it would if plugged into the wall. Not much different to doing a cold crash really. I reckon being a freezer it'd drop the brew 8 degrees in about 3 or 4 hours. Given it's also at the beginning, the heat created by the yeast activity would help keep the brew temp from dropping too far, and even if it did, it's lager yeast - it'll work down to about 4 degrees without going dormant.

It only takes my fridge about 6 hours to get it from 18 to 12 when I start the ramping down to lager temps. The air inside it would obviously be a fair bit under 12 degrees, possibly near zero, but the brew itself never really dips under 12 when the fridge turns off. It might drop 0.1-0.2 degrees but that'd be it. I may well be wrong but it sounds like you're making a lot of assumptions without actually having tried it to see what happens. Have you tried it taped under foam yet?

The advice to pitch lagers warmer is based on pitching a low cell count (for lagers), if you're pitching large amounts of yeast into them then they can and in my view should be pitched at or below fermentation temp.

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I've recently swapped from fridge to freezer. I can fit two fermenters and I've found that my "active" beer (the one being measured and directly controlled) is fine but the "passive" one (which has usually already been through primary fermentation) is usually a bit too cold. No big deal though I don't think - I just swap them and raise the temp a bit before bottling.

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G'day Shamus.

2 hours ago, Shamus O'Sean said:

I sandwich the probe between the base of the fermenter and the board it sits on.  Not taped and not under foam.

There are multiple ways to insulate the probe to read the wort temp accurately. It doesn't matter so much which method you use, only that NO part of the probe is taking temp readings of anything other than the wort. It is important to make sure of this or you will be receiving false readings, & this will have an effect on the outcome of your brews. The most accurate way to guarantee wort temp is to actually feed the probe directly into your fermenter so that it is completely surrounded by the wort.

2 hours ago, Shamus O'Sean said:

...Now, before someone goes off-tap about not being taped under foam and not best practice hear me out.

If I did tape it under foam it would be close to the temperature of the wort. Say 20 degrees to start with.  The freezer would kick-in and run until the sensor detected 11.5 degrees, essentially until the wort was at that temperature.

The fridges generally have an inbuilt mechanism that will shut off the compressor for "X" mins or so after a set period of running as to not burn it out. I can't remember if the temp controllers have a setting for that as it's been that long since I've had to fuddle around with those other settings.

2 hours ago, Shamus O'Sean said:

...Then the 11.5 degree wort and the minus 5 degree ambient air try to reach an equilibrium.  Therefore the wort temperature continues to drop. 

If you are bringing the temp down from a high gap against the temp you would like to ferment at, set the temp 1°C above the temp you would like to eventually ferment at. That will allow for the over-run from the colder ambient temp surrounding the fermenter that you speak of. The over-run generally goes past the set temp by more the larger the gap between pitching temp & the temp you've set to ferment at in your controller. Once it appears to stabilize reset the temp controller to the actual temp you wish to ferment at. Staggering your temp cooling of the wort can minimize this over-run.

2 hours ago, Shamus O'Sean said:

...It is then up to the air surrounding the freezer to eventually warm the wort and the probe inside of the freezer, through its own insulation and the foam enough to warrant turning on the freezer again.   By this time the wort may have got down to say 5 degrees for maybe a day.

Yeast are exothermic, & provided you haven't dropped below a temp they can operate in, they will quickly begin to generate heat as part of active fermentation.

2 hours ago, Shamus O'Sean said:

...By this time the wort may have got down to say 5 degrees for maybe a day.

Highly unlikely.

2 hours ago, Shamus O'Sean said:

...The way I do it allows the wort temperature to gradually drop to 11.5 degrees and I have found this equilibrium is reached in under a day.

Even when I have a decent gap between pitching temp & eventual ferment temp, I think the longest it has taken me is maybe 4½ - 5 hours.

2 hours ago, Shamus O'Sean said:

...Plus gives the wort a warmer start to encourage yeast growth.  Which corresponds to some advice to start lagers around 20 degrees then drop to 12 after about 12 hours.

Nothing wrong with that mate. 👍

Cheers & good brewing,

Lusty.

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Lusty,

The controllers do have a delay setting in them like what you describe but it doesn't do anything once the fridge is already on as it doesn't override anything in the fridge settings. It only works when the fridge has been turned off after the temp has reached the set point and it rises to the point it would kick back in too quickly, in which case it delays turning the fridge back on.

Examples from when I'm chilling yeast starters, and dangle the probe with the difference set to 2 degrees instead of the usual 0.3;

If the fridge is already on coming down from 2 to 0, I open the door, it warms up, close the door again and the fridge just goes along as normal down to 0, there is no delay initiated. In mine the compressor turns on and off every 5 minutes or so when it's actively chilling.

If the fridge has been turned off by the controller after reaching 0 degrees and I open the door straight away, again the temperature rises a few degrees but the controller prevents the fridge turning back on again until the delay time has passed.

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46 minutes ago, Otto Von Blotto said:

Lusty,

The controllers do have a delay setting in them like what you describe but it doesn't do anything once the fridge is already on as it doesn't override anything in the fridge settings. It only works when the fridge has been turned off after the temp has reached the set point and it rises to the point it would kick back in too quickly, in which case it delays turning the fridge back on.

Like I said mate, it's been a while since I've had to dabble with these settings on my controllers. My brew fridge operates as it should based on the original settings I programmed the controller with. When bringing the temp down from pitching temp to ferment temp the settings I have in place (or the base fridge settings) only allow the compressor to run for so long before cutting out for a rest. The only thing I change these days is the ferment temp from brew to brew based around what type of beer I'm brewing & the ferment temp requirements.

+1 to the rest of what you said.

Cheers,

Lusty.

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Yeah, it's not the controller turning the compressor on and off mate, it's the fridge itself doing it. When it's chilling a brew down to ferment or cold crash temps it's running as if it was plugged straight into the wall without a controller at all, so the compressor on/off cycle is controlled by the fridge itself. All the temp controllers do is turn the power on and off, they don't mess with the programming of the fridge. 

By the way, other than changing the difference when I chill yeast starters in there I don't change anything much either except the temperature for different ferments and of course cold crashing. 👍

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12 minutes ago, Otto Von Blotto said:

Yeah, it's not the controller turning the compressor on and off mate, it's the fridge itself doing it. When it's chilling a brew down to ferment or cold crash temps it's running as if it was plugged straight into the wall without a controller at all, so the compressor on/off cycle is controlled by the fridge itself. All the temp controllers do is turn the power on and off, they don't mess with the programming of the fridge. 

By the way, other than changing the difference when I chill yeast starters in there I don't change anything much either except the temperature for different ferments and of course cold crashing. 👍

I think you enlightened me to this the last time around. In my defence though I did suggest this to Shamus in my post to him.

A 'Ground Hog' day moment for both of us! 🤣

Cheers mate. 🙂

Lusty.

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Ho OVB & BL

Thanks for the comments.  You are both right.  A lot of us beginner stage brewers just talk about what we do, not necessarily what is right.

OVB - I have not tried to go from 20 to 12 with the probe under foam taped to the fermenter.  So I am making a lot of assumptions.  I do have a fermenter with foam taped to its side and have used it for lager brewing, but I stepped down the temperature in a couple of increments over 12 hours. 

OVB & BL - Dropping 20-12 may not harm the compressor.  The freezer may have its own cut-off feature to give it a break over that time.  I have not kept an eagle eye on it the whole time to know.  When trying to cool 20 litres of water from tap temperature to 2 degrees (for use on brew day) and checking 4 hours after I start, the freezer is running and generating heat around the top of the freezer.

OVB - I probably under pitch my lager yeasts.  Hence why I am okay to start them a bit warmer.

BL - I use a chest freezer and find that once the temperature has stabilised it stays that way.  I have left the freezer door open on a warm day (while I dry hop, take SG readings, etc.) and find that even after 10 minutes, the temperature in the bottom of the freezer has not gone up by half a degree.  I get the "feed the probe directly into your fermenter" bit, but once temperature is constant, everything in the freezer pretty much stays that way.

BL - I could do like you suggest and stagger the temperature drop to minimise the over-run.  I do this when cold crashing because I fear that the freezer does not have its own "fail-safe" to switch-off periodically to give itself a break.  I will have to google my freezer specs to find out.

OVB & BL - Me saying equilibrium is reached in under a day could mean 5-6 hours.  All I can say is: yeast pitched at 20 degrees at around 4pm.  By bedtime at 10pm it is not down to 12 degrees, maybe 14.  When I get up the next day it is at 12 degrees.  Un-der-a-day.

                 -  I think I have the delay on my controller set at about 4 minutes.  Probably have never changed it.

Prolly more than my 2 cents worth.

Don't get put off by us smart-aleck up-starts.  Keep up the good advice.

Cheers Shamus

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All fridges and freezers maintain an on/off cycle for the compressor. If they didn't then the thing would burn out very smartly. They all generate heat in various parts as well. My fridge is 60+ years old, original compressor, never had any repairs other than replacing the door seal a few years ago. It's been used as a brew fridge for about 6 years and shows no signs of slowing down anytime soon. 

Think of it this way: when it's dropping temps by a reasonable amount like that, the temperature controller doesn't exist. The unit is running the same way it would if it was plugged straight into the wall socket. It will cycle the compressor the way it's been designed to. All the controller is is an automated version of someone standing at the wall socket turning it on and off. It doesn't and cannot override the internals and cause the compressor to run non stop. You have nothing to worry about in that sense.

 

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Im thinking Shamus is on a winner here. What are we measuring when taped to side of vessel as opposed to just dangling the probe in the fridge or freezer. Because the temerature of the wort moves so slow. Im thinking we are trying to cool the wort when not required. Thanks Shamus i will give this a try.

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It's measuring the temp of the brew which is what we're trying to control. Dangling the probe in the fridge or freezer is useless because the ambient temperature doesn't always match up with the brew temp, especially during active fermentation. In that instance the brew is often a few degrees warmer than the surrounding air.

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1 hour ago, Titan said:

Im thinking Shamus is on a winner here.

Thanks Titan

I like my theory for gradually dropping the wort temperature to lager brewing temperatures without under-shooting the target temperature.  I accept that my fears of massive under-shooting are probably unfounded.

For brewers like Otto, who start their lagers at or just below lager brewing temperatures, having the probe taped to the fermenter under foam is a better idea.  Similarly, BL's idea of dangling it in the fermenter.  Both of these methods would pick up the temperature rise from active fermentation earlier than my approach and switch on the freezer/fridge to keep the fermenting temperature in the preferred range.  Once I have got the brew down to brewing temperature, the under the foam option would work best for me.

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Reading the above discussion reinforces my belief that home brewers tend to worry unnecessarily at times,or even tend towards superstition. Fridge and freezer compressors can and often do run continuously. They are controlled only by the thermostat which measures the temperature of air in the cabinet.. As others have noted,an external controller cannot force it to do more work than it would do without the controller. Relax and enjoy your fancy temperature control. I am lucky enough to live in a climate which is kind to brewers. Cheers.

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I believe freezers have more insulation, so might be more energy efficient, especially if you keep it in a shed. 

I have a small chest freezer myself, which can only fit one fermenter. One thing about it that I don't like is it is hard on the back. I like to ferment in glass, which weighs 6.5kg empty. Fill it with wort and it is about 29.5kg. I actually can't lift the carboy high enough to get it over the edge when it is full, so I only fill it to 18L, which saves me 5kg, and top it up at bottling time. If I accidentally fill it up too much I use a couple of chairs to get the carboy in: put the carboy on one, stand on the other, then hoist the carboy onto the edge of the freezer, get off the chair and lower the carboy into the freezer (while standing on the ground). 

I would not recommend a freezer to anyone with back trouble or a hernia. The freezer is showing no signs of breaking down, but I am getting a fridge next time.

Cheers,

Christina.

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Sometimes I do start them warm in cases where I forget to put the cube in the fridge overnight before pitching yeast the next day*. Granted, I'm only using a fridge but coming down to 10 degrees from low 20s I never see it drop more than a few tenths of a degree below the target temperature. Even in a freezer I highly doubt it would drop 7 degrees below target temperature with the probe taped under foam, the thing would have to be running for another couple of hours to achieve that. I'd say 1-2 degrees at the most, which won't be a problem at all.

*For summer brewing. In winter I used to put them in for a few hours but where we live now gets down close to zero overnight so left outside the wort would probably be at fermentation temp or close enough by itself. It'll be interesting to see what happens once winter comes. The last pale ale I did I put the cube in overnight as it was rather hot, but I left it too long before pitching it; it ended up being pitched at about 13 degrees but fermentation kicked off in the usual time and the beer was great. 

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