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Old 06-17-2012, 06:52 PM   #2741
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Hi

Wide hysteresis at the chamber wall does not equate to wide swing in a keg of beer. There's a *lot* of thermal mass in the keg. It averages out the air temperature. The air temperature is an average of the wall temperature. To be fancy about it, the keg acts as an integrator.

If you are sensing in a bottle of water, the chamber wall is already swinging quite a bit. Toss a thermocouple (or what ever) on the wall and watch it. Different parts of the wall will move different amounts, but they all swing quite a bit.

Bob
You are repeating what everyone else is saying, but applying it incorrectly. Everyone is saying that the freon, air, and everything in between gets much colder (and hotter) than the controlled vessel. The rest of us are just saying that trying to figure out what that temp swing is so it can be programmed into the controller is a whole lot more difficult than taping the probe to the vessel you want to control, setting the temp you want, choosing a reasonable diff value, and walking away. Not to mention that, given the diff range limit on these controllers, your method is certain to increase cycling.

For your approach, integrator is an awfully fancy name for a passive heat sink (keg) that will approach, or if your control system sucks, hover around, the average temperature maintained inside the freezer.


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Old 06-17-2012, 07:11 PM   #2742
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Fantastic idea! This thread is already so rambling and cluttered that newer members have a lot of trouble finding the info they need about the controller that this thread was started about.
As long as the 'probe on coil/wall' approach gets thoroughly ridiculed in this one. I saw his post the other day, and was tempted to comment. Since it seemed to go unnoticed, I let it be. When the guy still defended his strategy, even after several posts to the contrary, it now unfortunately needs to be beaten into submission.

There have already been a few people burn up their brand new chest freezers, some the first day, by taking the 'probe in air' advice that was being foisted ages ago as the best method by a few vocal people. The 'probe on coil' method is equally bad. The compressor killing "hot starts" may not be as big of an issue, but cycling is going to increase dramatically. How long would it take for the coil to exceed even the 10C max differential of these controllers- 20 seconds?


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Old 06-17-2012, 08:29 PM   #2743
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I just finished my keezer build and currently have my temperature probe just sitting at the bottom of the keezer. Its there mainly bc I'm waiting to brew my ESB and wanted to use the whitelabs vial as the container to submerge the probe in. I've been following this thread somewhat to find what is best for long term survival of my freezer.

What is an acceptable cycling time for the freezer? Right now I have my freezer set at 37 deg and it will kick on above 40 deg and usually carry the temperature down to 34. When it kicks on, its on for about 7 minutes and then kicks off for about 30 minutes. That seems like a lot of cycling to me. The keezer is in the house so it's not exposed to extreme temperatures. Also the collar is not insulated, I just used 2" pine behind 1" oak to make the collar.

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Old 06-17-2012, 09:12 PM   #2744
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Originally Posted by cwi View Post
As long as the 'probe on coil/wall' approach gets thoroughly ridiculed in this one. I saw his post the other day, and was tempted to comment. Since it seemed to go unnoticed, I let it be. When the guy still defended his strategy, even after several posts to the contrary, it now unfortunately needs to be beaten into submission.

There have already been a few people burn up their brand new chest freezers, some the first day, by taking the 'probe in air' advice that was being foisted ages ago as the best method by a few vocal people. The 'probe on coil' method is equally as bad. The compressor killing "hot starts" may not be as big of an issue, but cycling is going to increase dramatically. How long would it take for the coil to exceed even the 10C max differential of these controllers- 20 seconds?
Hi

I have indeed watched how the compressor cycles. It does not behave the way you think it does. It cycles in a very rational way and never gets anywhere near a "fast cycle burn up" situation.

Bob
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Old 06-17-2012, 09:33 PM   #2745
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Originally Posted by carlisle_bob

Hi

I have indeed watched how the compressor cycles. It does not behave the way you think it does. It cycles in a very rational way and never gets anywhere near a "fast cycle burn up" situation.

Bob
The "rational" way is massive temp swings from below-freezing to exceeding the temperature of the thermal mass. Most controllers don't allow anywhere near such a wide hysteresis, so even setting it to the controller's maximum will have far more frequent cycling than is ideal. And even if you can find a controller that allows for such a wide hysteresis, you're just making yourself play a ridiculous guessing game with regards to the stable temperature of the thermal mass, as opposed to being certain that the SERVING temp is *exactly* what you want (fermentation generates its own heat, so in that case you can't even maintain a stable temp).

Basically, there's no advantage to fixing it to the wall, but several disadvantages. As such, the superior method is clear. As cwi already said, it technically CAN offer better control, but it requires a far more advanced control system than these single-probe temp controllers we all use, so it's irrelevant for most of our purposes, and certainly irrelevant to this thread.
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Old 06-17-2012, 10:08 PM   #2746
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Originally Posted by carlisle_bob View Post
Hi

I have indeed watched how the compressor cycles. It does not behave the way you think it does. It cycles in a very rational way and never gets anywhere near a "fast cycle burn up" situation.

Bob
My previous opening comment needs repeating- read thoroughly.

I stated that 'probe in air' has the hot cycling issue, and your 'probe on coil' (or wall) should not have that issue, because it is attached to the coil which will continue to chill (or the wall which has some mass). The 'probe on coil' method is guaranteed to cycle more frequently than necessary because the probe will be chilled past the temp diff almost immediately, shutting off the freezer. The 'probe on wall' method, as long as the walls are not part of the evaporator, will behave better (though far from ideal), but the controller temp and diff settings still have to be homed in on by trial and error to get the desired beer temp and avoid freezing of smaller vessels.

If you try to add in the additional constraint of minimizing cycling, the tuning task becomes almost impossible. For the 'probe on vessel' approach, controlling cycling is simply a matter of choosing the largest differential that you can live with, and you have optimal cycling for that temp/diff.

Either way, on coil or on wall (which method you use isn't clear), your approach has zero benefits for a keezer or ferm chamber implementation.
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Old 06-17-2012, 10:39 PM   #2747
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Originally Posted by smittygouv30 View Post
I just finished my keezer build and currently have my temperature probe just sitting at the bottom of the keezer. Its there mainly bc I'm waiting to brew my ESB and wanted to use the whitelabs vial as the container to submerge the probe in. I've been following this thread somewhat to find what is best for long term survival of my freezer.

What is an acceptable cycling time for the freezer? Right now I have my freezer set at 37 deg and it will kick on above 40 deg and usually carry the temperature down to 34. When it kicks on, its on for about 7 minutes and then kicks off for about 30 minutes. That seems like a lot of cycling to me. The keezer is in the house so it's not exposed to extreme temperatures. Also the collar is not insulated, I just used 2" pine behind 1" oak to make the collar.
The best advice to avoid killing your freezer is to go get blackout drunk so you forget anything carlisle_bob posted.

The main thing that helps avoid cycling is to have the probe on something thermally massive, and also a lot of thermal mass in the freezer- never run one empty. Equally important is to never leave the probe hanging in the air, especially with a small temp diff setting. The single most important thing to prevent instant death of your compressor due to a 'hot start' caused by unusual conditions is to max out the ASD of the controller (10 min?).

With a proper setup, cycling can be controlled by the temp diff setting. This setting also determines the swing of your ferming beer, so there is a tradeoff between a tight temp variance, and compressor cycling. Most people are happy using a 0.5C diff setting, since the thermal mass of the vessel minimizes cycling enough to be acceptable.

There is no reason to wait until you have a yeast vial to use some thermal mass to control cycling. Just tape the probe to any thermal mass, like a bottle of beer, then insulate it. That is the method commonly used for keezers. There are more than a few people that have their probe directly in liquid, but many don't trust the chinese probes to remain waterproof for long submersion periods.

For fermenting, tape it to the vessel wall (like the side of a carboy), and put insulation over that. Additional passive thermal mass, provided it is already at ferm temp, can help reduce cycling further, but a fan may be needed to prevent undershoots as well as help with heat transfer from the passive mass to the ferm vessel.

One scenario you wouldn't want extra thermal mass in the freezer is when you are crash cooling a batch, since it will add additional time to reach the final temp.
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Old 06-17-2012, 11:33 PM   #2748
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Quote:
Originally Posted by carlisle_bob View Post
Hi

I have indeed watched how the compressor cycles. It does not behave the way you think it does. It cycles in a very rational way and never gets anywhere near a "fast cycle burn up" situation.

Bob
The cycling you're experiencing probably isn't frequent enough to burn up the compressor quickly, but I'm confident that it cycles considerably more often than the few times a day mine cycles. By your own admission you had to fiddle with both the probe placement and hysteresis settings to achieve your desired serving temp and compressor cycle rates. If you're happy with how your probe placement performs, that's great, but please stop trying to convince others of it's benefits when there clearly aren't any.

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Originally Posted by cwi View Post
The best advice to avoid killing your freezer is to go get blackout drunk so you forget anything carlisle_bob posted.

The main thing that helps avoid cycling is to have the probe on something thermally massive, and also a lot of thermal mass in the freezer- never run one empty. Equally important is to never leave the probe hanging in the air, especially with a small temp diff setting. The single most important thing to prevent instant death of your compressor due to a 'hot start' caused by unusual conditions is to max out the ASD of the controller (10 min?).

With a proper setup, cycling can be controlled by the temp diff setting. This setting also determines the swing of your beer, so there is a tradeoff between a tight temp variance, and compressor cycling. Most people are happy using a 0.5C diff setting, since the thermal mass of the vessel minimizes cycling enough to be acceptable.

There is no reason to wait until you have a yeast vial to use some thermal mass to control cycling. Just tape the probe to any thermal mass, like a bottle of beer, then insulate it. That is the method commonly used for keezers. There are more than a few people that have their probe directly in liquid, many don't trust the chinese probes to remain waterproof for long submersion periods.

For fermenting, tape it to the vessel wall (like the side of a carboy), and put insulation over that. Additional passive thermal mass, provided it is already at ferm temp, can help reduce cycling further, but a fan may be needed to prevent undershoots as well as help with heat transfer from the passive mass to the ferm vessel.

One scenario you wouldn't want extra thermal mass in the freezer is when you are crash cooling a batch, since it will add additional time to reach the final temp.
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Old 06-18-2012, 02:13 AM   #2749
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Originally Posted by cwi
The best advice to avoid killing your freezer is to go get blackout drunk so you forget anything carlisle_bob posted.

The main thing that helps avoid cycling is to have the probe on something thermally massive, and also a lot of thermal mass in the freezer- never run one empty. Equally important is to never leave the probe hanging in the air, especially with a small temp diff setting. The single most important thing to prevent instant death of your compressor due to a 'hot start' caused by unusual conditions is to max out the ASD of the controller (10 min?).

With a proper setup, cycling can be controlled by the temp diff setting. This setting also determines the swing of your ferming beer, so there is a tradeoff between a tight temp variance, and compressor cycling. Most people are happy using a 0.5C diff setting, since the thermal mass of the vessel minimizes cycling enough to be acceptable.

There is no reason to wait until you have a yeast vial to use some thermal mass to control cycling. Just tape the probe to any thermal mass, like a bottle of beer, then insulate it. That is the method commonly used for keezers. There are more than a few people that have their probe directly in liquid, but many don't trust the chinese probes to remain waterproof for long submersion periods.

For fermenting, tape it to the vessel wall (like the side of a carboy), and put insulation over that. Additional passive thermal mass, provided it is already at ferm temp, can help reduce cycling further, but a fan may be needed to prevent undershoots as well as help with heat transfer from the passive mass to the ferm vessel.

One scenario you wouldn't want extra thermal mass in the freezer is when you are crash cooling a batch, since it will add additional time to reach the final temp.
Wow, thanks a bunch. That is extremely helpful information. I'll have to mess with the settings to see about changing the ASD. I don't remember seeing it when I connected my controller.
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Old 06-18-2012, 02:43 AM   #2750
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Wow, thanks a bunch. That is extremely helpful information. I'll have to mess with the settings to see about changing the ASD. I don't remember seeing it when I connected my controller.
ASD (Anti-Shortcycle Delay) is called 'compressor delay' in the STC-1000 manual, and is F3 in the menu. There is no logical reason not to max it out at 10 min. It is also automatically activated at power up to prevent a hot start in the event of a momentary power loss.


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