Keezer temerature probe placement

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AnimatedGIF

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I am in the process of building a keezer and would like to know the best place to place the temperature probe (using an inkbird).
From what I have read, there are a few options:
  1. Tape to the side of the keg (I think this is actually more related to bre fridges than dispense systems, so maybe not relevant)
  2. Dangle somewhere in the keezer
  3. In a jug of water at the bottom of the keezer (pretty sure I have seen that mentioned on here).
I don't think option 1 is something that anyone does, from what I have seen, but I could b wrong. I woud have thought it would result in the keezer freezing as the volume of liquid (up to 19L) would take a long time to drop to the desired temperature.
Option 2 is my preference I think, though I feel this will result in the keezer coming on and off as the temperature of the air in the freezer reaches the target, then the beer essentially warms the air up again (thus making the beer cooler), keezer comes back on and the cycle continues until the beer and the air are the same temperature.
With option 3, I am not convinced that the temperature of a small volume of water is representative of a large volume of beer, and so I feel like the same thing would happen as in option 2, albeit less freqent freezer on-off cycles. (Now I think about it, that may in fact be the advantage of this method).

Of course, there may be ptions I haven' considered. I am also aware that there is likely a temperature difference between the top and bottom of the keezer. As my kes dispence from the bottom, I imagine that as ong as the bottom is the desired temp, it should be all good? I know come use fans inside to even it out, but not sure I want to go that far.
 

JockyBrewer

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Personally I think it's worth having a little bit of a damping effect on the on/off cycles by attaching it to something rather than dangling in air, although sticking it in liquid does seem to shorten the life of the inkbird probes.

I've got mine cable tied to a bottle full of water that sits on the compressor hump of my keezer. I have my Inkbird set to 5-7c and it doesn't need to cycle more than once an hour. I have a fan to circulate air in the keezer and right at the top of the collar where the tap shanks are varies between 5-9c.
 

AnimatedGIF

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Personally I think it's worth having a little bit of a damping effect on the on/off cycles by attaching it to something rather than dangling in air, although sticking it in liquid does seem to shorten the life of the inkbird probes.

I've got mine cable tied to a bottle full of water that sits on the compressor hump of my keezer. I have my Inkbird set to 5-7c and it doesn't need to cycle more than once an hour. I have a fan to circulate air in the keezer and right at the top of the collar where the tap shanks are varies between 5-9c.
Thanks. That's a good idea to have a bottle of water inside rather than placing the prob in water. I might give that a go.
How do you power the fan? I have one socket available for the inkbird, but no other power source.
 

HarryFlatters

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I drilled a hole in the top of a plastic bottle, filled it with starsan and put the probe in that, sat on the shelf of the compressor box thing so it's broadly half way down from the top. I used bluetac to cover the hole and hold the cable in place. Seems to work ok.

I bought USB powered PC cooling fans and mounted them onto cheap light switch surrounds, then used L brackets to fix them to the collar. I glued lengths of tumble dryer vent hose to the 'in' side of the fans and draped the hose to the bottom of the keezer, so that the fans draw up cold air and blow it at the shanks. I had foaming issues early on, which was partly due to line balancing and partly due to having a temperature differential in the shanks.
 

xozzx

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I leave mine dangling in the air, I have the inkbird set with 2C range max-min so the freezer isnt on/off too much and have a pc fan wired into an old charger cable with same voltage as the fan, this is plugged into one of those timer socket things (link) so the fan is only on about 50% of the time. After about 2 years still no issues.
 

JockyBrewer

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Thanks. That's a good idea to have a bottle of water inside rather than placing the prob in water. I might give that a go.
How do you power the fan? I have one socket available for the inkbird, but no other power source.
It’s a 12v PC fan that i wired to an old 12v phone charger. It’s plugged into a 4 port extension cable that is attached to the back of my keezer collar, which also powers the inkbird.
You want it running the whole time, not just when the inkbird brings the freezer on.
 

AnimatedGIF

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Coming back to this again nearly a year later, I see I never thanked posters of post #4-6 - how rude of me.
Thank you all athumb..
 

The-Engineer-That-Brews

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Just for reference I think that any of your options will work fine. But for preference I’d tape it to the side of a small water bottle (ideally a metal one) in the bottom of the keezer. I’d avoid dangling it in the water because some of those type-k Inkbird sensors aren’t sealed up too well.
As you say, a dispense setup is a bit simpler in that the brew itself isn’t generating heat so it’s less important to have the sensor closely coupled to the temperature of the liquid itself.
In general the more time delay there is between the compressor coming on and the temperature of the sensor starting to fall, the bigger the overshoot there will be in the air temp inside the keezer. In reality this won’t affect the temperature of the kegs hardly at all because they’ve got such a high thermal mass, but I suppose in an extreme case it might temporarily freeze up the beer lines if they run close to the cooling elements and the temp is set low.
Finally I would say that I’ve done a comparison between dangling the sensor in the brew versus strapping it to the outside of the keg (under a bit of wadded up kitchen cloth) and the difference is minimal (less than 0.5°)
 

johncrobinson

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Control theory states that the monitored proccess should be in as close thermal contact as possible,To avoid time lag effects.
Plastic in its many forms is not a good conductor of heat,Many temp controllers use AI techniques to try to amealiorate this but its still a "fudge".
 

AnimatedGIF

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I did dangled it for ease with perfectly good results in respect to beer experience, but going to go for the option of taping to a bottle. I think I have a metal bottle somewhere.
But what did you decide to do?
Also, so many typos in the OP. I guess I must have had a few when I wrote it.

I came back to this as I am making fermentation fridge at the moment, though I appreciate controlling temperature of fermenting wort vs temperature of kegged beer is a different kettle of fish...
 
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