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mfraier

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I am looking to get a controller for my extra fridge for brewing and was wondering if anyone has used these and how they like them. AHS has the digital ones for 79, I thought that would work pretty good.
 

MalFet

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I am looking to get a controller for my extra fridge for brewing and was wondering if anyone has used these and how they like them. AHS has the digital ones
for 79, I thought that would work pretty good.
There are a lot of threads with more specifics, but Johnsons are exceeding common around here and are generally well liked.
 

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I have two analog johnsons and aside from the numbers on the dial being pretty much meaningless they work very well. I just have to use a thermometer and get it set where I want it.
 
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mfraier

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Will it work with a regular refrigerator? I see that the advertising says turn any freezer into.....I assume a fridge would work just the same?
 

MalFet

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Will it work with a regular refrigerator? I see that the advertising says turn any freezer into.....I assume a fridge would work just the same?
Sure. Obviously, the fridge is going to have a different operating range than the freezer, but so long as you are looking to maintain an operating temp appropriate to your fridge you're good. A lot of people prefer using fridges to freezers at above freezing temperatures due to moisture concerns.
 

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I have two analog johnsons and aside from the numbers on the dial being pretty much meaningless they work very well. I just have to use a thermometer and get it set where I want it.
You know, I have been meaning to post about this for 6 months or so, and haven't. I built a fermentation chamber and have an analog johnson controller (can't recall the model). The numbers are way off, like by 5-10 degrees. Meaningless, like you said.

Is this the norm with these controllers? I just use a thermometer to check the beers temp to help dial in the right setting...so it works, but man are those numbers useless. I thought I just had a bum unit.

Other than that, the unit works great and keeps a steady temp.
 
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mfraier

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Midwest has it for 75 normally.
75 Plus shipping.....AHS 79 and buy a kit and they ship it to my door for free ( orders over 100 ship free) .:rockin:

I heard the digitals are more accurate than the analog, but if I have to use a therrmometer to dial in the temp no big deal.
 

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75 Plus shipping.....AHS 79 and buy a kit and they ship it to my door for free ( orders over 100 ship free) .:rockin:

I heard the digitals are more accurate than the analog, but if I have to use a therrmometer to dial in the temp no big deal.
Digital is easier to read accurately than Analog. But either is only as good as the device feeding the readout.
 

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I am going with the "in the air" method but beyond that where does one put the end of the probe in a chest freezer...just anywhere? Tape it in place? Let it hang? etc?
 

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Dumb question but would a refridge be better for ales since they ferment at a higher temp? Or do people use freezers because they are more flexible in regards to temps?
 

RukusDM

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I am going with the "in the air" method but beyond that where does one put the end of the probe in a chest freezer...just anywhere? Tape it in place? Let it hang? etc?
I let mine hang roughly at the level of the fermenter
 

RukusDM

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Dumb question but would a refridge be better for ales since they ferment at a higher temp? Or do people use freezers because they are more flexible in regards to temps?
Well in my case a freezer is what I had in my basement. I have a fridge but its in a detached garage and its way below freezing in there so I cant use it till spring when it warms up.
 

Krelja

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google for the johnson A419 and you can find it usually around $50 without the wires. A cheapo extension cord and homebrewtalk will have it wired up cheaper than you can by at any brew shop
 

MalFet

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I am going with the "in the air" method but beyond that where does one put the end of the probe in a chest freezer...just anywhere? Tape it in place? Let it hang? etc?
If you leave it dangling in the air, you end up measuring the ambient temperature and not the temperature of your beer. During vigorous fermentation, this can be off by a lot...I see five degrees sometimes. Some people (including myself) have a thermowell inside their fermentors, but in reality just taping the sensor to the fermentor and then covering it with some insulation is probably good enough for most purposes.
 

MalFet

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Dumb question but would a refridge be better for ales since they ferment at a higher temp? Or do people use freezers because they are more flexible in regards to temps?
Not a dumb question, actually. You can certainly run a freezer at above-freezing temperatures without too much difficulty. Some people report problems with condensation in chest freezers operating above 32F, but there is plenty of discussion on this board about how to deal with that problem. People often like chest freezers because of their shape...they're quite space efficient for fermentation purposes. Ultimately, either works.
 

RukusDM

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If you leave it dangling in the air, you end up measuring the ambient temperature and not the temperature of your beer. During vigorous fermentation, this can be off by a lot...I see five degrees sometimes. Some people (including myself) have a thermowell inside their fermentors, but in reality just taping the sensor to the fermentor and then covering it with some insulation is probably good enough for most purposes.
I don't understand how this would work well. If you measure the beer temp and you had just put it in the fridge, you might have a temperature in the 60's or 70's.

If you are doing a lager, the fridge would run until the beer came down to 50's or 40's. It would be below freezing in there before the beer came down to temp as it might take hours to drop. It seems like it would over shoot a mile wouldn't it?
 

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Or measure the temperature of the fridge for a day and then tape it to the fermentor. Still sounds like it would be un-stable.
 

MalFet

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I don't understand how this would work well. If you measure the beer temp and you had just put it in the fridge, you might have a temperature in the 60's or 70's.

If you are doing a lager, the fridge would run until the beer came down to 50's or 40's. It would be below freezing in there before the beer came down to temp as it might take hours to drop. It seems like it would over shoot a mile wouldn't it?
The reason that doesn't tend to happen is because water has a huge thermal mass relative to air. Air has a volumetric heat capacity of 0.001297 joules per cubic centimeter per degree, whereas water is at 4.1796 (so says wikipedia). So in other words, if you had a perfectly insulated box that was half liquid and half air and then cooled the air by 30 degrees, it would barely move the temperature of the water.
 

RukusDM

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The reason that doesn't tend to happen is because water has a huge thermal mass relative to air. Air has a volumetric heat capacity of 0.001297 joules per cubic centimeter per degree, whereas water is at 4.1796 (so says wikipedia). So in other words, if you had a perfectly insulated box that was half liquid and half air and then cooled the air by 30 degrees, it would barely move the temperature of the water.
That was my point, there is so much lag that the temperature of the fridge or freezer would be perhaps below zero before the beer got into the 40's.

I would expect large swings in freezer or fridge temperature because of the lag. I'm sure it appears to work, but from a controls viewpoint, not what I would call a constant system.

Anyway, I'm sure it works for you or you wouldn't do it.
 

MalFet

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RukusDM said:
That was my point, there is so much lag that the temperature of the fridge or freezer would be perhaps below zero before the beer got into the 40's.

I would expect large swings in freezer or fridge temperature because of the lag. I'm sure it appears to work, but from a controls viewpoint, not what I would call a constant system.

Anyway, I'm sure it works for you or you wouldn't do it.
I see what you're saying, but having your air temp move around isn't the problem you suggest it is (so long as we're talking about a standard sized fridge and not some mega-walk-in). Volatility in air temperature does not lead to volatility in beer temperature in this case. If you measure the air temp and control your compressor on that basis, what ends up happening is that you get more oscillation in your beer temp, faster cycling of your compressor, and slower overall cooling.

There's no lag because there's no such thing as "the temperature of the fridge", only the temperature of the things inside the fridge. That sounds like nit-picky semantics, but its actually an important distinction. In theory and in practice, your fridge temp will meet equilibrium at the average temperature of the things inside it, weighed by each thing's thermal mass. For all practical purposes, the temperature of the beer _is_ the temperature of the fridge.

It's kind of like tying a jetski to a cruise ship. If you want to track the movement of the system, you have to track the cruise ship. The jetski is essentially a trivial force.

Give it a shot, if you have the equipment. Have on probe measuring air and another measuring liquid. Run the compressor according to one for one fermentation and the other for the next. You get far greater beer temperature stability running off the liquid probe. You'll also get quicker cooling and less cycling of your compressor. I did this experiment with an arduino when i first got my fridge, and the difference was significant. And from a controls viewpoint, this really is the standard practice -- I own a food production facility and had this point argued to me a few years ago by the engineer who did my temp system.
 

RukusDM

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I see what you're saying, but having your air temp move around isn't the problem you suggest it is (so long as we're talking about a standard sized fridge and not some mega-walk-in). Volatility in air temperature does not lead to volatility in beer temperature in this case. If you measure the air temp and control your compressor on that basis, what ends up happening is that you get more oscillation in your beer temp, faster cycling of your compressor, and slower overall cooling.

There's no lag because there's no such thing as "the temperature of the fridge", only the temperature of the things inside the fridge. That sounds like nit-picky semantics, but its actually an important distinction. In theory and in practice, your fridge temp will meet equilibrium at the average temperature of the things inside it, weighed by each thing's thermal mass. For all practical purposes, the temperature of the beer _is_ the temperature of the fridge.

It's kind of like tying a jetski to a cruise ship. If you want to track the movement of the system, you have to track the cruise ship. The jetski is essentially a trivial force.

Give it a shot, if you have the equipment. Have on probe measuring air and another measuring liquid. Run the compressor according to one for one fermentation and the other for the next. You get far greater beer temperature stability running off the liquid probe. You'll also get quicker cooling and less cycling of your compressor. I did this experiment with an arduino when i first got my fridge, and the difference was significant. And from a controls viewpoint, this really is the standard practice -- I own a food production facility and had this point argued to me a few years ago by the engineer who did my temp system.
I understand the idea. I work in the controls field. Mostly in the area of Motor Drive systems, Position control, Servos etc.

Temperature systems are also usually Proportional output controls with Integral and Derivative.
 

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I'm going to give this a try. My lager is about ready for a dialectal rest, and while the fermenter is out of the Freezer, I'm going to put a carboy of water in there and try this.

My only concern was that using Dead band Control like we are would produce a sinusoidal temperature of decreasing magnitude peaks until it came to equilibrium because of the lag.

If I was doing my lagering at 32 degrees I would be worried about throwing a carboy in there that has a temperature of 60 to 65 and have the thermocouple attached to it. The overshoots are what I'd be concerned with until it came to equilibrium.

Like I said, I'm sure it works or you wouldn't be doing it, I just want to see what the swings look like.
 

MalFet

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I understand the idea. I work in the controls field. Mostly in the area of Motor Drive systems, Position control, Servos etc.

Temperature systems are also usually Proportional output controls with Integral and Derivative.
Certainly not trying to doubt your credentials :mug: I'm sure your system nets good beer, but every couple of days there's a new thread on here that goes "why does my hefe taste like bananas? my garage is 68 degrees!". Soon as they stick their temp probe next to their wort rather than in the air, the problem goes away.

If you have the means to do the calculus on your system it would certainly be fun. If you had a proper model of the thermodynamics, you could probably do some cool stuff predicting temperature changes and the like. But, like you mention, that depends on proportional output control and processing a mite more sophisticated than a love controller. We only got on/off switches around here :D

We're well beyond the level of control necessary for good fermentation here. Then again, that's the national pastime of this place...over-thinking beer :ban:
 

MalFet

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I'm going to give this a try. My lager is about ready for a dialectal rest, and while the fermenter is out of the Freezer, I'm going to put a carboy of water in there and try this.

My only concern was that using Dead band Control like we are would produce a sinusoidal temperature of decreasing magnitude peaks until it came to equilibrium because of the lag.

If I was doing my lagering at 32 degrees I would be worried about throwing a carboy in there that has a temperature of 60 to 65 and have the thermocouple attached to it. The overshoots are what I'd be concerned with until it came to equilibrium.

Like I said, I'm sure it works or you wouldn't be doing it, I just want to see what the swings look like.
Sinusoidal temperature of the air, or of the liquid? Because I did get more variation in air, but significantly less in the water (which is the only temp I care about). In my experience, the effect is more pronounced when you've got heat coming from the fermentor because of active yeast, but I'll be interested in your results from water anyway.

The overshoot you mention is the heart and soul of the question. Theoretically, you certainly do get overshoot, but because of the thermal mass ratios it's hundredths of a degree. Practically, I never observed any overshoot. It could be slightly more of a problem if you've got an old fridge with walls that absorb a lot of heat, but I still suspect it wouldn't be much. I've got a pretty crappy fridge.
 

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Certainly not trying to doubt your credentials :mug: I'm sure your system nets good beer, but every couple of days there's a new thread on here that goes "why does my hefe taste like bananas? my garage is 68 degrees!". Soon as they stick their temp probe next to their wort rather than in the air, the problem goes away.

If you have the means to do the calculus on your system it would certainly be fun. If you had a proper model of the thermodynamics, you could probably do some cool stuff predicting temperature changes and the like. But, like you mention, that depends on proportional output control and processing a mite more sophisticated than a love controller. We only got on/off switches around here :D

We're well beyond the level of control necessary for good fermentation here. Then again, that's the national pastime of this place...over-thinking beer :ban:
I'm definatly going to try this today and see what happens. This is my bain in life as a person who works in the engineering field. I always question things until the data supports the theory.

My wife just smiles and shakes her head sometimes hahahhaa ;)

Cheers :mug:
 

MalFet

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I'm definatly going to try this today and see what happens. This is my bain in life as a person who works in the engineering field. I always question things until the data supports the theory.

My wife just smiles and shakes her head sometimes hahahhaa ;)

Cheers :mug:
Mine just wonders why I can't buy beer at the store like normal people :mug:
 

RukusDM

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Sinusoidal temperature of the air, or of the liquid? Because I did get more variation in air, but significantly less in the water (which is the only temp I care about). In my experience, the effect is more pronounced when you've got heat coming from the fermentor because of active yeast, but I'll be interested in your results from water anyway.

The overshoot you mention is the heart and soul of the question. Theoretically, you certainly do get overshoot, but because of the thermal mass ratios it's hundredths of a degree. Practically, I never observed any overshoot. It could be slightly more of a problem if you've got an old fridge with walls that absorb a lot of heat, but I still suspect it wouldn't be much. I've got a pretty crappy fridge.
Well, not speaking from experience yet, I would expect 2 issues. The first would be the freezer would go into full freeze mode and run for several hours until the temperature of the liquid came within the deadband of the controller and shut off. Now we have a freezer that is in the minus 20's or lower I don't know how cold they get.

This would produce issue number two. The temperature of the liquid would now begin going lower than setpoint, perhaps by allot until it ran out of thermal energy. It would then begin a slow climb back up until it passed the deadband of the controller again and turn the freezer on again. Repeat and Rinse until the temperature peaks flatten out.

Now this might not be a problem with a Fridge as it doesn't have the capacity to go as low a temperature as a freezer does. This might be a issue with a freezer only. We'll see. Perhaps its not a issue at all but I'll find that out.

In warmer months I'll be using this controller on my fridge in the garage. Its below freezing in my garage now so it won't work well as a heater ;)
 

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When using a freezer with a controller, what is the best "temp" to set the freezers temperature gauge.

I've read some push it all the way, as cold as it could possibly get, while others dial in the middle of the range, or on the low side.

Using an auxiliary controller, is there a difference in where the stock temperature dial is set?
 

MalFet

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ultravista said:
When using a freezer with a controller, what is the best "temp" to set the freezers temperature gauge.

I've read some push it all the way, as cold as it could possibly get, while others dial in the middle of the range, or on the low side.

Using an auxiliary controller, is there a difference in where the stock temperature dial is set?
For the majority of freezers that have a simple on/off thermostat, you want to set it on max to be "always on". Your auxiliary controller should be the thing powering the fridge on and off, and you don't it to be fighting with an internal thermostat.
 

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For the majority of freezers that have a simple on/off thermostat, you want to set it on max to be "always on". Your auxiliary controller should be the thing powering the fridge on and off, and you don't it to be fighting with an internal thermostat.
MalFet, I just pulled my carboy out for a Diacetal Rest. I put a 5 Gallon Carboy full of water in there and taped the thermocouple to the bottle.

Last I looked after putting it in the temp was about 62 degrees. I have the controller set for 50. We'll see what happens.

I'll start a new thread if I see anything interesting. Sorry for the Hijack. :mug:
 

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MalFet, the bottle is now down to 45 Degrees with no cycle. It definitely works well. It definitely didn't behave as I expected.

I measured the bottle temp and the water temp at the same time. The water was about 10 to 12 degrees behind the temperature of the Glass carboy.

The water is now down to about 50, so 5 degrees behind. The fridge was very cold, my digital thermometer couldn't read it. I did have a analog in there but it went below zero and wound back around to 250degrees on the dial so I don't know how cold it got.

The lag between the liquid temp and the bottle temp may have stabilized it. When the freezer turned off the cold was still being absorbed by the liquid and bottle.

In any event, I'll be using this method now. Thanks for suggesting this.
 

MalFet

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MalFet, the bottle is now down to 45 Degrees with no cycle. It definitely works well. It definitely didn't behave as I expected.

I measured the bottle temp and the water temp at the same time. The water was about 10 to 12 degrees behind the temperature of the Glass carboy.

The water is now down to about 50, so 5 degrees behind. The fridge was very cold, my digital thermometer couldn't read it. I did have a analog in there but it went below zero and wound back around to 250degrees on the dial so I don't know how cold it got.

The lag between the liquid temp and the bottle temp may have stabilized it. When the freezer turned off the cold was still being absorbed by the liquid and bottle.

In any event, I'll be using this method now. Thanks for suggesting this.
Very interesting. I'm glad the liquid stayed stable, but I'm surprised by how much difference there was with the carboy surface. Thanks for doing the science. I definitely learned something new! :mug:
 
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