Keezer, stc query

[Nibbo]

I'm with the submerse in water group. I run two keezers and both are setup with the probe in sanitised water. One is a Briess 1.5kg malt extract tub full of water and the other uses an empty keg that doubles as a reservoir for the flooded font. It's about 1/3 full. Too much volume and you'll find the keezer will freeze your beer lines as the freezer runs longer to chill it down to temp.

 

[Crusty]

I know a lot of people subscribe to this theory but it just seems wrong to me. The liquid in the freezer will eventually stabilize to the same temperature as the ambient temperature in the freezer (given that it is not fermenting) However I think even a stubby of water is too much insulation for the probe. If you put the stubby of water if the freezer I would think that by the time it gets down to 2deg, the freezer will be at minus 10, by the time the stubby returns to 4 degrees the freezer will be at 15. I think you want the ambient temp swinging 2-3 deg, and the liquid temp will struggle to swing by a single degree.

The liquid in the keezer is what matters to me. It doesn't matter if, or, the freezer is running as in your example of minus 10 to achieve 2deg in the bottle.
The temp probe from the STC is measuring the liquid in the keezer, which is what we want. The same goes for insulating your fermenter against the ambient temp of your fridge. Just letting it hang in there during fermentation & setting the STC to say 18deg is pointless. The fridge air temp will be 18 but the wort inside the fermenter will be hotter than that. This is why it's important to insulate the probe from the ambient temperature.
The keezer is exactly the same. Ambient temp doesn't matter, it's the liquid temp that counts.
I had mine set up just hanging in there with no fan & the temperature at the bottom of the keezer was a few degrees colder than the top where my beer line was.
Even after installing a computer fan, the compressor was on & off far too often. Insulating that probe in the water stabilized the temperature with far less compressor start ups. The probe is in 3deg water & my beer is 3deg as well.

 

[Ghizo]

ImageUploadedByAussie Home Brewer1447068197.769041.jpg
This is what I used on my Keezer and it works perfectly.

Was in difficult to install?
I have seen these, it was my other option

 

[klangers]

The difference between a fermentation fridge and a beer storage fridge is that the fermenatino fridge has to pull down an internal source of heat - the ferment. This would benefit from direct (probe in wort) measurement as the heat comes from inside the wort.

A beer storage fridge simply keeps the heat external to the fridge (and indeed from the fridge operation itself) out. I don't see really much difference in performance between "liquid" measurements and "ambient" measurements as everything will reach equilibrium as the heat is coming from outside the beer. The heat comes in mostly when you open the fridge door and all the cold air rushes out. So, the two scenarios are:

• Air measurement - since the cold air has rushed out of the fridge door and replaced with warm air, the ambient probe will trigger the fridge to pull down until this air is the correct temperature. The kegs will reach equilibrium with this air as there is no internal heat source in the kegs and hence no driver for temperature differential.
• Liquid measurement - the cold air rushes out of the fridge and warm air comes in. This warms the kegs/bottle a bit and the fridge reacts to pull these back down.

Both work, but I don't subscribe to the postulation that one needs to put their keezer/beer fridge temp probe in a thermal mass (which is all you're doing) as this simply adds hysteresis. I would be simply adding a minimum compressor cycle time control if you're worried about the compressor.

 

[jeremy]

I can see where people are coming from with regard to adding thermal mass for the purposes of stopping the compressor kicking in everytime you open the door when you are retrieving a beer from an upright fridge, that makes sense. With a chesty being operated as a keezer I dont have this issue because:

a) you dont open it often, and
b) even when you do, the cold air doesnt pour out like it does with an upright.

However do regular fridges and freezers have their regular thermostats sitting in some sort of thermal mass? I would think they would work on the same principles as the STC with the built in min and max settings and compressor time lag safety setting? Wouldn't you expect the compressor to kick in after you retrieve a beer and all the cold air escapes, just like you hear the compressor on your regular fridge kick in when you leave the door open for a few seconds?

The liquid in the keezer is what matters to me. It doesn't matter if, or, the freezer is running as in your example of minus 10 to achieve 2deg in the bottle.
The temp probe from the STC is measuring the liquid in the keezer, which is what we want. The same goes for insulating your fermenter against the ambient temp of your fridge. Just letting it hang in there during fermentation & setting the STC to say 18deg is pointless. The fridge air temp will be 18 but the wort inside the fermenter will be hotter than that. This is why it's important to insulate the probe from the ambient temperature.
The keezer is exactly the same. Ambient temp doesn't matter, it's the liquid temp that counts.
I had mine set up just hanging in there with no fan & the temperature at the bottom of the keezer was a few degrees colder than the top where my beer line was.
Even after installing a computer fan, the compressor was on & off far too often. Insulating that probe in the water stabilized the temperature with far less compressor start ups. The probe is in 3deg water & my beer is 3deg as well.

However, this to me is just plain wrong. I can understand that you want the liquid a certain temperature, and the ambient temperature is not your predominant concern, yep, makes perfect sense. However the best way to control your liquid temperature is to keep the ambient temperature at the temperature that you want your liquid to be. In a keg freezer this is simple, just leave your temp probe in the open air within the keezer and set your min and max temps to a few degrees apart (one or two either side of your desired liquid temps) and the liquid will end up being correct. I can peoples point regarding your glass of water, but all you are introducing an external min and max to your controller by putting your probe in a thermal mass of limited size, accounting for any minor variations in the temperature between the top and bottom of your freezer by allowing the glass of water to keep a temperature relative to the air moving around it, ie the air may be 3 degrees warmer at the top, and 3 degrees colder at the bottom at any given point in time, however as long as you keep the air blowing around, and have a little thermal mass around your probe, this wont matter. I would argue that if there is a 3 degree variation between the bottom and top of your freezer, and you are circulating the air, then you could just widen the kick-in and kick-out temperatures on your temp control and it would do exactly the same thing, but horses for courses, both will achieve the same result.

Where you lose me entirely though is when you suggest that the air temp is unimportant and the liquid temp is what matters. It sounds to me like you would happily install your probe in a thermowell within your fermenter in your fermenting fridge (or inside your keg in your freezer if possible), and use this to run your temp control, because you are interested in the temperature in the liquid, not the ambient temp. This is just wrong. Yes, you are more interested in the temperature of the liquid, but no this does not mean that you want to have your probe inside your fermenter, or even emulate this by having it in water. The reason for this is that by the time your liquid reaches the desired temperature the ambient temperature will be well and truly beyond the desired temperature (ie the fridge will be at 2 degrees by the time the liquid gets to 20), then the fridge will kick out but the temperature in the fermenter will continue to go down to say 18 degrees because it will take forever for the fridge to get back up to warmer temps. If you have a heating element involved, that will then kick in, and bring the temperature in the fridge up to 40 degrees while it struggles to get the beer back up to 20, the heating will then kick out, but the temperature in the fermenter will continue to rise while the fridge tries to get back down again, and so on. So what you would have is fridge temps swinging from 2 to 40, and fermenter temps swinging from 18 to 23, this is hysteresis at work. Control the ambient temp within 3 degrees and the fermenter temp will scarcely vary at all. So even though you are more interested in controlling the liquid temperature, the best way to do this is by getting the ambient temperature as close to correct as possible. Obviously with a fermenter you might need to keep the ambient temps a bit lower than what you want your liquid to be due to heat from fermentation, but putting your probe IN your beer just doesn't make sense.

 

[Crusty]

We could argue until the cow's come home so I won't bite into it anymore. I think both ways will work but I don't believe controlling the ambient temperature is the best way to go.The most accurate way to measure your fermentation or liquid inside your keezer is via a thermowell.
Ambient temperatures will rise & fall far quicker than the thermal mass we are trying to control so controlling ambient is to me, well, pointless.
As an example, if I set my STC to 18deg ambient, it would take some time for the liquid temperature to stabilize at 18, but lets just say it's now sitting nicely at 18deg. I go & open the fridge & all of a sudden, the STC detects it's not 18deg anymore so it kicks in. The thermal mass certainly hasn't changed but now we want to cool it some more. Another problem is the temperature of the fermenting liquid. It will be higher than the actual ambient temperature because as we all know, fermentation creates it's own heat, so although the ambient is at 18deg, the inside wort temperature will be hotter than that. If you left the fridge closed with the fermenter now probably at 20deg+ , how long do you think that thermal mass will take to trigger the STC into realizing the air temperature surrounding it is too high? It would take ages & the wort is fermenting away at far too hot a temperature because the STC is controlling the surrounding air.
This is the reason we insulate the STC probe against the fermenter so we don't get any interference from the ambient temperature. The wort or liquid temperature needs to be controlled, not the surrounding air. It's well discussed & proven that measuring ambient temperature is not the best way to control fermenting wort.
Thermowells are used for this very reason & it's of course why commercial breweries use glycol jacketed fermenters in an ambient environment.
It's the liquid temp that matters, not the surrounding air. I've tried both & immersing the probe in liquid is more accurate with less activity from the compressor.
I use a Sanke fermenting kit with a thermowell & it's definitely the most accurate way to control the temperature. The same rule applies for my keezer. The liquid that the STC probe is in, is the same temp as my beer & that's what I'm chasing.

 

[Mattrox]

I can see where people are coming from with regard to adding thermal mass for the purposes of stopping the compressor kicking in everytime you open the door when you are retrieving a beer from an upright fridge, that makes sense. With a chesty being operated as a keezer I dont have this issue because:

a) you dont open it often, and
b) even when you do, the cold air doesnt pour out like it does with an upright.

However do regular fridges and freezers have their regular thermostats sitting in some sort of thermal mass? I would think they would work on the same principles as the STC with the built in min and max settings and compressor time lag safety setting? Wouldn't you expect the compressor to kick in after you retrieve a beer and all the cold air escapes, just like you hear the compressor on your regular fridge kick in when you leave the door open for a few seconds?


However, this to me is just plain wrong. I can understand that you want the liquid a certain temperature, and the ambient temperature is not your predominant concern, yep, makes perfect sense. However the best way to control your liquid temperature is to keep the ambient temperature at the temperature that you want your liquid to be. In a keg freezer this is simple, just leave your temp probe in the open air within the keezer and set your min and max temps to a few degrees apart (one or two either side of your desired liquid temps) and the liquid will end up being correct. I can peoples point regarding your glass of water, but all you are introducing an external min and max to your controller by putting your probe in a thermal mass of limited size, accounting for any minor variations in the temperature between the top and bottom of your freezer by allowing the glass of water to keep a temperature relative to the air moving around it, ie the air may be 3 degrees warmer at the top, and 3 degrees colder at the bottom at any given point in time, however as long as you keep the air blowing around, and have a little thermal mass around your probe, this wont matter. I would argue that if there is a 3 degree variation between the bottom and top of your freezer, and you are circulating the air, then you could just widen the kick-in and kick-out temperatures on your temp control and it would do exactly the same thing, but horses for courses, both will achieve the same result.

Where you lose me entirely though is when you suggest that the air temp is unimportant and the liquid temp is what matters. It sounds to me like you would happily install your probe in a thermowell within your fermenter in your fermenting fridge (or inside your keg in your freezer if possible), and use this to run your temp control, because you are interested in the temperature in the liquid, not the ambient temp. This is just wrong. Yes, you are more interested in the temperature of the liquid, but no this does not mean that you want to have your probe inside your fermenter, or even emulate this by having it in water. The reason for this is that by the time your liquid reaches the desired temperature the ambient temperature will be well and truly beyond the desired temperature (ie the fridge will be at 2 degrees by the time the liquid gets to 20), then the fridge will kick out but the temperature in the fermenter will continue to go down to say 18 degrees because it will take forever for the fridge to get back up to warmer temps. If you have a heating element involved, that will then kick in, and bring the temperature in the fridge up to 40 degrees while it struggles to get the beer back up to 20, the heating will then kick out, but the temperature in the fermenter will continue to rise while the fridge tries to get back down again, and so on. So what you would have is fridge temps swinging from 2 to 40, and fermenter temps swinging from 18 to 23, this is hysteresis at work. Control the ambient temp within 3 degrees and the fermenter temp will scarcely vary at all. So even though you are more interested in controlling the liquid temperature, the best way to do this is by getting the ambient temperature as close to correct as possible. Obviously with a fermenter you might need to keep the ambient temps a bit lower than what you want your liquid to be due to heat from fermentation, but putting your probe IN your beer just doesn't make sense.

The air changes temperature far more quickly than the large mass of liquid in it. If the air in the fridge was 2 and fermenter/keg was 20 when the fridge shut off the temp of the liquid will hardly move. But the air temp will swing up towards 20 rather quickly. Trying to control the air temp in a narrow range will cause the fridge motor to kick in far more often. This is why fridges/freezers have such a wide hysteresis.

Measure the liquid as that's what you drink.

If your liquid is too warm you want the fridge to kick in. To drop the temperature of the beer, there must be a temperature difference. Let the air temp drop as much as you need to get the beer cold. Unless you have a super super cold air temp the beer temp will hardly drop after the motor shuts down. Especially so with a couple of kegs in the keezer.

If you are still worried, organise a 2 probe STC 1000+ and limit the temperature difference between the air and the beer. It will be kinder to the keezer.

 

[Moad]

I'll have some logging in my ferment fridge soon, I'll do an experiment of controlling wort temp with probe

A) in the air
B) in the thermowell

Should settle it if it hasn't been done already

 

[spog]

As per the OP, no mention of fermentation control was made (keezer) so the question remains.....
It's an interesting topic, opening a keezer does not allow cold/ cooled air to spill out as would happen using a fridge ,yeah opening a keezer does allow warmer air to into the keezer bit to my mind no where near as much as a fridge.
This is interesting to me as I can see both sides of the " argument" but if the kegs are in the keezer the contents of the keg/kegs will reach equilibrium ,temp,given time.

 

[osprey brewday]

Ive logged an ale fermentation before on day 3 or 4 vigorous churning space temp was 8c,fermenter thermowell 18.3c, set point 17.2 ,diff 0.2 controller (dixel) this was a 50 lt ferment in about 28c ambients the compressor ran for 6 hours straight during peak to keep on top of the heat load as only a domestic with not much hp. Controlling probe was in centre of fermenter. Circulating fan used and air probe was in air flow of fan. The main reason i use a thermowell in fermenter is to prevent run away temps during peak fermentation and i can have a 0.2 differential with no risk of compressor damage. Off topic to keezer discussion but sort of related

 

[jeremy]

We could argue until the cow's come home so I won't bite into it anymore. I think both ways will work but I don't believe controlling the ambient temperature is the best way to go.The most accurate way to measure your fermentation or liquid inside your keezer is via a thermowell.
Ambient temperatures will rise & fall far quicker than the thermal mass we are trying to control so controlling ambient is to me, well, pointless.
As an example, if I set my STC to 18deg ambient, it would take some time for the liquid temperature to stabilize at 18, but lets just say it's now sitting nicely at 18deg. I go & open the fridge & all of a sudden, the STC detects it's not 18deg anymore so it kicks in. The thermal mass certainly hasn't changed but now we want to cool it some more. Another problem is the temperature of the fermenting liquid. It will be higher than the actual ambient temperature because as we all know, fermentation creates it's own heat, so although the ambient is at 18deg, the inside wort temperature will be hotter than that. If you left the fridge closed with the fermenter now probably at 20deg+ , how long do you think that thermal mass will take to trigger the STC into realizing the air temperature surrounding it is too high? It would take ages & the wort is fermenting away at far too hot a temperature because the STC is controlling the surrounding air.
This is the reason we insulate the STC probe against the fermenter so we don't get any interference from the ambient temperature. The wort or liquid temperature needs to be controlled, not the surrounding air. It's well discussed & proven that measuring ambient temperature is not the best way to control fermenting wort.
Thermowells are used for this very reason & it's of course why commercial breweries use glycol jacketed fermenters in an ambient environment.
It's the liquid temp that matters, not the surrounding air. I've tried both & immersing the probe in liquid is more accurate with less activity from the compressor.
I use a Sanke fermenting kit with a thermowell & it's definitely the most accurate way to control the temperature. The same rule applies for my keezer. The liquid that the STC probe is in, is the same temp as my beer & that's what I'm chasing.

Haha, yeah I think we will have to agree to disagree because I think your argument is fundamentally wrong, we control ambient temps BECAUSE they rise and fall quicker. If your probe is in your keg, the temperature of the liquid will need to change a degree or two before the fridge kicks in and corrects it, however if you do it with the ambient temperature the liquid temp will hardly change at all because it wont get the chance.

As I said in my last post, if you control ambient in a keg fridge, ambient will swing 1 deg to 3 deg, liquid will swing from 1.8 to 2.2. Do it the other way round and your liquid will swing from 1 to 3 and your ambient will swing from 10 to minus 10. Its common sense.

The only reason for putting a probe in a stubby is to introduce a small amount of thermal mass around the probe to account for sharp drops or increases in temp or differences in temp around your fridge, you aren't trying to emulate the measurement of liquid temps in your keg your just trying to stop the compressor cycling too often.

 

[jeremy]

To possibly concede a point in the argument I would say that if you put a thermowell inside your keg and set the fridge to kick in at 1.9 and kick out at 2.1 then I would say this would achieve the same result (as hysteresis would mean it would then push out to 1.8 and 2.2 say) AND it would give you the exact temperature of the liquid in your freezer which would be ideal. Not sure if the temp controllers have this fine an adjustment or if the probe is that accurate. In any case I would say control of the environment temp is still a better idea, that way you don't have to wait for the liquid to change. Control the environment rather than the object, its how fridges work. This may help to illustrate where I am coming from...

 

[Mattrox]

Haha, yeah I think we will have to agree to disagree because I think your argument is fundamentally wrong, we control ambient temps BECAUSE they rise and fall quicker. If your probe is in your keg, the temperature of the liquid will need to change a degree or two before the fridge kicks in and corrects it, however if you do it with the ambient temperature the liquid temp will hardly change at all because it wont get the chance.

As I said in my last post, if you control ambient in a keg fridge, ambient will swing 1 deg to 3 deg, liquid will swing from 1.8 to 2.2. Do it the other way round and your liquid will swing from 1 to 3 and your ambient will swing from 10 to minus 10. Its common sense.

The only reason for putting a probe in a stubby is to introduce a small amount of thermal mass around the probe to account for sharp drops or increases in temp or differences in temp around your fridge, you aren't trying to emulate the measurement of liquid temps in your keg your just trying to stop the compressor cycling too often.

If you set your hysteresis to 0.3 the liquid goes from 4 to 4.3 for example. Not a degree or two. I defy anyone to tell the difference between beers poured at those temperatures. Then above 4.3 the fridge kicks in and it cools back to 4.

The air temperature is irrelevant. Sure the air temp drifts up..., let's say to 10. But the fridge soon sorts it out and the beer is at 4 and the fridge cuts out. Sure the air temperature might be -10, but that soon drifts up with minimal effect on beer temp. If the beer over shoots to 3.9 can you really tell?

Trying to keep the air at 4 C means the motor switches on and off repeatedly. The other way the motor is running for longer and off for longer and the beer is still cold.

Keep the probe at beer temp. Control that. Don't abuse the fridge compressor. Set the temp you want for pouring and appropriate hysteresis. If you are really worried about temp overshoot use 2 probes and do not allow fridge temp to drop "too low".

There are very few accounts of overshoot causing problems using this method.

 

[jeremy]

If you set your hysteresis to 0.3 the liquid goes from 4 to 4.3 for example. Not a degree or two. I defy anyone to tell the difference between beers poured at those temperatures. Then above 4.3 the fridge kicks in and it cools back to 4.

The air temperature is irrelevant. Sure the air temp drifts up..., let's say to 10. But the fridge soon sorts it out and the beer is at 4 and the fridge cuts out. Sure the air temperature might be -10, but that soon drifts up with minimal effect on beer temp. If the beer over shoots to 3.9 can you really tell?

Trying to keep the air at 4 C means the motor switches on and off repeatedly. The other way the motor is running for longer and off for longer and the beer is still cold.

Keep the probe at beer temp. Control that. Don't abuse the fridge compressor. Set the temp you want for pouring and appropriate hysteresis. If you are really worried about temp overshoot use 2 probes and do not allow fridge temp to drop "too low".

There are very few accounts of overshoot causing problems using this method.

See my next post...

Any fridgies out there tell me if a regular fridge has the temperature probe in a thermal mass? If you are worried about compressor cycling use the hysteresis and compressor delay settings on your temp controller, that's what they're there for.

 

[jeremy]

For anyone interested in this topic, this guy has done all the hard work for us when it comes to the compressor cycling/power saving component of the discussion:

http://www.homebrewfinds.com/2014/10/temperature-probe-place-to-immerse-or-not-to-immerse.html

Apparently we are all wrong, we should be zip tying the probe to a beer can! Be good to see an expansion on this using hysteresis and compressor delay settings on the temp controller and the effect it has inside the keg!

 

[Mattrox]

See my next post...

Any fridgies out there tell me if a regular fridge has the temperature probe in a thermal mass? If you are worried about compressor cycling use the hysteresis and compressor delay settings on your temp controller, that's what they're there for.

We are not controlling a "normal" fridge. Throw a temp probe in the fridge and have a look. Then do the same with a chest freezer. Remember that a fridge keeps food "cold" not at 5 +or - 1 degree or whatever you choose to serve your beer at. And a freezer just has to keep things below 0. That could range from -5 to -25.

 

[jeremy]

We are not controlling a "normal" fridge. Throw a temp probe in the fridge and have a look. Then do the same with a chest freezer. Remember that a fridge keeps food "cold" not at 5 +or - 1 degree or whatever you choose to serve your beer at. And a freezer just has to keep things below 0. That could range from -5 to -25.

End of the day mate, if you control your environment within a few degrees your beer will acclimatize. Use hysteresis and delay settings on your temp controller to prevent compressor cycling. Simple.

 

[Mattrox]

But the dude had no way of checking if the beer he was keeping varied in temperature with any his methods. He was referencing the ambient temp. If they all keep the beer at 38F with little variation then you choose the most cost effective method.

 

[jeremy]

But the dude had no way of checking if the beer he was keeping varied in temperature with any his methods. He was referencing the ambient temp. If they all keep the beer at 38F with little variation then you choose the most cost effective method.

Yeah correct, I mentioned that it was only really referencing the ambient temperatures and it would be interesting if he included the temps inside the keg. Its just covering the immersion of the probe and its effect on ambient temperatures. Interesting nonetheless.

 

[spog]

Slightly OT , but when it comes to the keezer operating I have been thinking about a fan than kicks in when the cooling cycle does,so a fan blows air onto the motor/ compressor to help keep it/them cool.
The fan would help with the life of motor etc but also help move air around the keezer walls ( especially if its enclosed in a decorative casing ), maybe a 12 volt fan.
Is there an inline automatic switch or what ever they are called available ?
If so how would it be done ?
Cheers.