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Old 05-03-2011, 09:30 PM   #21
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Originally Posted by SixFoFalcon View Post
Since my original posts, I've changed my settings a bit, due in part to Catt22's suggestions.

Currently I have the ASd (anti-short cycle delay) bumped up to 10 minutes. This comes in handy when I'm doing lots of keg swapping & cleaning, or when I have parties and people are lifting the lid to get bottled beers, look inside, etc. My chest freezer isn't getting any younger, and anything I can do to ease the load on the compressor will benefit me in the long run.

I omitted the water vessel for the probe. I was cleaning everything out and replacing old hoses one day, and I decided I was sick of the probe flopping around all over the place and getting in the way whenever I move things around in there. Also, when you think about it, it's unnecessary and just complicates things. Once you allow everything to settle in, and you have a couple kegs in there cooled to serving/aging temps, the only thing that's changing when you open the lid is that the air inside is warming up. So it makes sense to only run the compressor enough to cool the air back down, and in doing so, the beer stays at the right temp. In that light, the probe should really just be sampling the inside air temp.

Even adding a full warm keg to the mix doesn't change this much, as you just want to allow the existing cold kegs to stay where they are, and only run the compressor enough to keep the inside air from drifting up in temperature. By the next day, everything is at equilibrium and your older kegs of beer never changed temperature more than a few degrees. With the water vessel acting as a "buffer", you are instead allowing the air to warm up, and the liquids inside the water vessel and kegs to warm up a couple degrees before the compressor kicks in and cools things down. You end up with a "hysteresis" loop where the compressor is coming on later than you want, and shutting off later than you want, resulting in wider temperature changes. Better to use the ASd to prevent the rapid on/off of the compressor when opening/closing the lid frequently and allow the thermostat to respond more quickly in normal situations so the inside air temp stays stable.

I still have 0 as the offset, and 2 degrees F as the differential. I've been serving my beers warmer (48-52), which is more appropriate for many styles, and also allows me to cure meats in there.
Your logic is a bit flawed. Having the probe in air will result in much more frequent cycling of the compressor for a given temp variance. The "probe in air" can still maintain a tighter temp variance of the beer, even with a larger temp diff, but it is harder to figure out the offset caused by the avg temp realized, which is what all passive bodies will average out to. The temp diff needs to increase when the probe is to "in air", to protect against frequent cycling, and decrease when "in water" to prevent increased temp swings.

If the lid is opened, the air will warm up, but the beer won't. Given time, the beer will lower the air temp easily without gaining any significant temp. Adding warm kegs, or controlling ferments (or raising orchids or curing meats) complicates matters. Something has to give.

For chilling a warm keg- fastest: probe in/on the warm keg; easiest on the compressor- probe on an existing keg. There are several intermediate strategies for balancing chilling speed vs. compressor life.

For controlling ferm temps- on the vessel wall is the majority opinion.

For controlling finished beer- in/on something small enough to prevent the smallest vessel from freezing or overcarbing, and larg enough to prevent frequent cycling.

With the probe in/on a liquid filled vessel, the compressor comes on for longer periods less frequently. Any vessel smaller than the probe vessel will get colder than the probe vessel, however. The smaller the probe vessel, the more frequent the cycling is, and vice versa. Something smaller than a keg and bigger than a bottle is a good range. The bottles just need to kept from freezing, and partial kegs from overcarbing.

The ASD is only a safety feature. It should not be considered as part of normal control strategy.
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Old 05-03-2011, 09:46 PM   #22
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Originally Posted by SixFoFalcon View Post
At any rate, a little air circulation inside the freezer should really minimize any thermostat lag and eliminate any stratification of the air, so it's a win-win for my dual-purpose kegerator/curing chamber.
You have minimized lag (or increased effective thermal response) of the sensor, but may have also increased cycling. It is hard to know exactly without testing, or a bunch of modeling. The air movement will increase the response of the sensor, but there are other variables. When the freezer is chilling, the existing thermal mass in the keezer will also be moderating/warming the air during that phase. During the "off" phase, the air movement around the keg will also moderate the air temps by chilling the air. For chilling a warm keg, the fan will increase cycling, but will get the keg to temp faster.

Either way, you could do your compressor a big favor by putting the probe in/on a vessel. The fan is a good idea either way since temps stratify so easily in a chest freezer.
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Old 05-03-2011, 09:51 PM   #23
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Originally Posted by Catt22 View Post
Whether you have it set to cut in or cut out at the set point doesn't make any difference except that the offset will be much different. The offset being what the beer temp actually is vs. what you set the controller to. The differential setting will affect the actual temp as well. I prefer to measure the beer temp and if it's too warm I turn the controller down and up if it's too cold.
Differential is the temp range to maintain- Setpoint + Diff= compressor on, or on some controller setpoint + 1/2diff = on, setpoint -1/2diff = off.

Offset can be used to calibrate the sensor, or compensate for the temp difference between the sensor temp and the body being controlled temp. This is just a convenience feature, it just combines the offset with the setpoint.
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Old 05-03-2011, 10:15 PM   #24
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Originally Posted by SixFoFalcon View Post
My chest freezer isn't getting any younger, and anything I can do to ease the load on the compressor will benefit me in the long run.

With the water vessel acting as a "buffer", you are instead allowing the air to warm up, and the liquids inside the water vessel and kegs to warm up a couple degrees before the compressor kicks in and cools things down. You end up with a "hysteresis" loop where the compressor is coming on later than you want, and shutting off later than you want, resulting in wider temperature changes.
If the temp diff is set to 1F, the compressor will come on when that is reached, and turn off when the setpoint is reached. This is not "later", since the air temp is irrelevant. There will be some overshoot after shutoff due to relative thermal inertia of the keezer (freon, walls, air, etc) to the mass of the keezer contents. This is usually fairly small, ~1F, and less for larger vessels and higher total mass of the contents. There is also some delay/overshoot caused by the stratification within the vessel if a thermowell is used. That is why taping to the outside of the vessel is popular. It serves to prevent overshoot by being partially influenced by the keezer air, while still accurately measuring the vessel internal temp.

Quote:
Originally Posted by SixFoFalcon View Post
Better to use the ASd to prevent the rapid on/off of the compressor when opening/closing the lid frequently and allow the thermostat to respond more quickly in normal situations so the inside air temp stays stable.
The ASD is specifically to prevent compressor "hot starting" when there is still pressure in the high lines. It is not a device/parameter to reduce cycling.
Instantaneous air temps are not important, only the avg. Faster response + probe in air = more frequent cycling than is necessary.


Quote:
Originally Posted by SixFoFalcon View Post
I still have 0 as the offset, and 2 degrees F as the differential. I've been serving my beers warmer (48-52), which is more appropriate for many styles, and also allows me to cure meats in there.
If all you need is a 2-3F range, that can be accomplished with a 1F diff and the probe in/on a mid sized vessel, and your compressor cycling will be reduce dramatically. You could also do the same thing (reduce cycling) with the probe in air, increasing the diff to 4-6F, and determining the offset (setpoint - avg). Either way, the beer temps could still be maintained within a 2-3F range, or less.
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Old 05-03-2011, 10:20 PM   #25
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I'm not sure I should go any deeper into an "in theory..." discussion on this, since there are so many variables involved. What I will say is that from my experiences over the past couple of years, I like it better without the liquid vessel for the probe. It may just be due to the way I'm using the setup (the frequency & duration of lid opening, adding warm kegs, dispensing bottled beers, curing meats, etc.) but nothing you have presented here immediately compels me to change the way I have my particular system configured.

What sort of setup are you running? Maybe that will help put your comments into context so I can understand better.

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Old 05-03-2011, 10:26 PM   #26
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Hey SixFoFalcon,

FYI, I've been running some tests just for the heck of it. The first run I had the controller probe submerged in a one gallon jug of water. This resulted in a 3.4 *deg temp swing also measured in that same one gallon jug. The temp swing should be less in a full keg or a keg containing more than one gallon. Fan ran continuously. The differential was set to 1*F and the Asd to 12 minutes. The cycles were much longer than 12 minutes, so the Asd was never activated even when the freezer was opened.

The second test was run with the controller probe in the air stream of the continuously running fan and the differential set to 1*F. The temp swing in the one gallon jug was very small with this configuration, only 0.3*F. Again, kegs with a larger volume should vary even less. I set the Asd to 5 minutes, but it only comes into play if I open the freezer lid before the time has lapsed since the last cycle.

Next two tests will be similar with actively fermenting beer. I can log min/max temperatures, but I have no way to keep track of the compressor run times. I do have a Kill-A-Watt meter hooked up. The freeszer is using very little power. Only 3.04 kwh over the past 109 hours. That's only about 5-10 cents per day depending on what the power costs are in your area.

I'll post an update when I get around to running the tests with a fermenter.
The critical data missing from this is compressor cycling. The total on time will be very similar for any probe placement since a fixed amount of heat is being removed. The number of cycles is the big issue, since that is what is likely to kill the compressor.
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Old 05-03-2011, 10:45 PM   #27
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Quote:
Originally Posted by SixFoFalcon View Post
I'm not sure I should go any deeper into an "in theory..." discussion on this, since there are so many variables involved. What I will say is that from my experiences over the past couple of years, I like it better without the liquid vessel for the probe. It may just be due to the way I'm using the setup (the frequency & duration of lid opening, adding warm kegs, dispensing bottled beers, curing meats, etc.) but nothing you have presented here immediately compels me to change the way I have my particular system configured.

What sort of setup are you running? Maybe that will help put your comments into context so I can understand better.
These are not theories. These are the Laws of Thermodynamics. If you are experiencing something that appears to defy them, an experiment can help find out why, but it isn't going to change them.

I don't have any data logging, or min/max sensors, but I had it out with Catt22 in another thread with a guy who did have logging stuff. Putting the probe in a vessel, he reduced cycling by 50% with less than a 1F variance increase due to overshoot, and that was in an 8oz glass. It would be less overshoot with the probe in a larger vessel, and less cycling.

You are cycling your compressor much more than is necessary, even to maintain the temp variance you currently have. You can place the probe where ever you like, but it contradicts the peppering of the "I love my compressor" statements scattered throughout the post. No one knowledgeable recommends setting a temp diff of 2F with the probe in air.

It also doesn't change that instantaneous air temp is irrelevant, and only avg air temp is relevant when controlling the air to control beer temps (as long as the beer temp stays within variance limits, that is). The avg will not (usually) be the setpoint, and that is what offset can be used for, or the setpoint adjusted to account for it.

For fermenting, putting the probe on/in the vessel is the only "hands off" way to control ferm temps accurately with a typical controller. Putting the probe in air for ferm'ing requires continually adjusting the controller setpoint to account for the varying difference between air and wort temps during the exothermic fermentation phase. This is due to using a secondary indicator, the surrounding air, as the controlled medium.

If you are doing multiple uses in a single keezer, it is very difficult to have a single probe placement without some compromises. For balancing priorities, or choosing a optimized placement for a scenario, it helps to understand what forces are at work.
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Old 05-04-2011, 01:58 AM   #28
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Interesting. Anyone else care to chime in?

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Old 05-25-2011, 03:22 AM   #29
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Quote:
Originally Posted by SixFoFalcon
Interesting. Anyone else care to chime in?
Yeah sure, I use a thermometer. :-p

In all seriousness I just bought a JC A419ABG-3C and am just trying to figure out how I should set the damn thing (jumper config, etc)... Didn't mean to stumble upon a thermodynamic meeting of the minds. It's like James Prescott Joule & Baron Kelvin are locked in a room debating what the best flavor of ice cream is while everyone else went off to Rudolf Clausius's crib for the keg party.

Hey - you asked for a chime-in; you got it.
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Old 05-25-2011, 09:18 PM   #30
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You could print out the instruction manual for the A419, and take it over to the keg party.

The discussion was more about sensor placement than a specific controller. I don't own an A419, but have seen many conflicting posts about how to set the jumpers, parameters, etc. I would cross reference a few threads on it to get a consensus, or just RTFM myself to know for sure (which I just did, and took me less time than it probably took you to write your post).

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