For those using ferm chambers.

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johnsnownw

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I've waited to post this until I've had consistent results over several brews. I used to use some bubble wrap to isolate the temperature probe from ambient. I now use these two products instead:

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So, the method is as such:

1. Tape the probe to the carboy/bucket.
2. Tape the pipe wrap over the probe (about 4" long strip)
3. Tape the duct insulation over the pipe wrap (About a 5" X 12" piece)

This has given me very good temperature isolation, and has kept my temps within 1° of what I've set. I re-use the same pieces, so this material will last you a long long time. It's a small investment for the results I've been getting.

Anyway, hope someone finds this useful.
 
I use long velcro straps I got at Lowes (3 three foot x 2" straps for $4 iirc) and 4" square pieces of inch thick closed cell foam sheet out of some random appliance carton to pin probes to carboys in the ferm fridge and kegs in the keezer. Takes seconds to install, easily repositioned, totally reusable - and immune to sweating vessel syndrome ;)

Cheers!
 
I use long velcro straps I got at Lowes (3 three foot x 2" straps for $4 iirc) and 4" square pieces of inch thick closed cell foam sheet out of some random appliance carton to pin probes to carboys in the ferm fridge and kegs in the keezer. Takes seconds to install, easily repositioned, totally reusable - and immune to sweating vessel syndrome ;)

Controllers have always read within a half-degree of both LC strips and my Fluke IR thermometer...

Cheers!
 
I’ve often wondered, what’s the insulation for? The one time I did it I put a strip of duct tape on the glass and taped the probe to that. It worked fine, corresponding well with the beer temperature. If I remember correctly the compressor was 5 minutes on, 20 minutes off.

It seems to me that the probe will be strongly correlated to the carboy temperature and weakly to the air temperature. If we start out with the probe and the carboy at the same temperature, the refrigerator air is going to have to be really cold to have much effect. If the beer is still warmer than the set point, conduction will soon start another cycle.

It may shorten the compressor on/off cycle but the duty cycle will be the same. Shorter, more frequent cycles will produce the same average temperature but with tighter regulation.

Isn’t that a good thing?
 
The idea is to use your beer's temperature to control the ambient temperature. To do that you need to isolate your beer temperature from the ambient. The initial fermentation puts out quite a bit of heat, so your beer might be 2-5 degrees warmer than ambient. The best way to isolate is probably a probe inserted into the beer, but then you have sanitation and extra equipment needs. Putting it on the side with insulation is easy enough and still isolates well enough for many brewers.

Edit: Not sure why you would think the probe temp would correlate so strongly with the carboy (I am assumig we are using a carboy here) instead of the air. If its uninsulated the majority of the probe is seeing ambient/air while only a small portion is touching the carboy.
 
I’ve often wondered, what’s the insulation for? The one time I did it I put a strip of duct tape on the glass and taped the probe to that. It worked fine, corresponding well with the beer temperature. If I remember correctly the compressor was 5 minutes on, 20 minutes off.

It seems to me that the probe will be strongly correlated to the carboy temperature and weakly to the air temperature. If we start out with the probe and the carboy at the same temperature, the refrigerator air is going to have to be really cold to have much effect. If the beer is still warmer than the set point, conduction will soon start another cycle.

It may shorten the compressor on/off cycle but the duty cycle will be the same. Shorter, more frequent cycles will produce the same average temperature but with tighter regulation.

Isn’t that a good thing?

Well, I use a chest freezer. I can tell you that there is a large discrepancy, initially, as my freezer brings down the wort to the temperature I wish to ferment.

For instance, when I put the wort in the freezer at 74°, but set the temp. controller to 68°, the freezer will bring ambient down in the 30's before the wort hits the target. Now if you don't have insulation around the probe, it's going to kick off the freezer before the wort is actually sitting at 68°, due to influence of ambient on the probe. As the greater the difference in temperature between ambient and wort, on a probe designed to use the total circumference of the probe to measure, will have a greater impact on that measurement. The cylindrical probe has far more of its surface area impacted by ambient than the small footprint against the "flat" carboy.

You would most likely run into this issue when fermentation is at it's height, with the fridge/freezer trying to keep up with heat produced by the yeast.
 
Try it and see. You’d be surprised. The conductance of air is .025, glass is .800. Plus there’s tape over it, so it’s not much exposed to air. Am I the only one that’s ever tried this?

As for big adjustments, I would temporarily bypass the controller and watch the temp. When it gets close, go back to the controller.

The way you’re doing it obviously works, it’s just that it could be better for no cost.

As an example, let’s say you have a 1F difference on your controller. If you can trick it into running twice as many cycles, you have half the difference, with less than half the overshoot (thermal inertia).

Yeast hate hysteresis. They told me so. They also prefer Celsius, but that’s another topic.
 
Hmmm...I use bubble wrap. I folded it up about 3 or 4 times into a square, wrapped the square neatly in duct tape, and I fasten it to the side of my fermenter with painters tape (sealing it off on 3 sides). Slide the probe down in there and voila. Works pretty good for me!
 
I use a (clean) sock. I fold it a few times, place it over the probe and tape it with some blue painters tape. Seems to work for me.
 
Wynne-R,
For big adjustments I agree with you that manual control is the most energy efficient because its hard not to overshoot with an on-off control system and a large temperature change.
As for the best results once you have reached your target temperature, its tricky because there is no perfect set up IMO. Since the beer is not being mixed there is a gradient from hot in the center to cold on the outside. Put your probe in the center of the carboy, you get cold sides. Put your probe on the side, you get a warm center.
For the foam vs no foam around the probe, if your temperature sensor is not getting 100% of its temperature measurement from the beer there is no way it can control that temperature as well, even you believe it is only a negligible difference. It may well be negligible in your set up but if, for example, there was a fan blowing on your temp sensor it would respond much more quickly to ambient changes while the bulk of the beer has not seen a significant change.

Edit: After re-reading this it sounds a bit hostile That was not my intent, its just the clearest way I can express the ideas I am trying to get across.
 
Since the beer is not being mixed there is a gradient from hot in the center to cold on the outside. Put your probe in the center of the carboy, you get cold sides. Put your probe on the side, you get a warm center.

Ah, but it is being mixed. Anyone who has watched their fermentation in action (and honestly, who hasn't?) can see that the yeast is rigorously churning the wort. Yes, it sits still after fermentation is complete, but temperature control at that point is far less critical.
 
RoadKing said:
YO! Are you copying me? Thats exactly what I do. Blue painters tape and all......LOL

Ha ha. I keep a roll of electrical tale over the fridge and tape over all the parts if the probe. It's sealed off from ambient temps. Seems pretty good.
 
Ah, but it is being mixed. Anyone who has watched their fermentation in action (and honestly, who hasn't?) can see that the yeast is rigorously churning the wort. Yes, it sits still after fermentation is complete, but temperature control at that point is far less critical.

Good point, I'll give you that one.
 
For the foam vs no foam around the probe, if your temperature sensor is not getting 100% of its temperature measurement from the beer there is no way it can control that temperature as well, even you believe it is only a negligible difference. It may well be negligible in your set up but if, for example, there was a fan blowing on your temp sensor it would respond much more quickly to ambient changes while the bulk of the beer has not seen a significant change.

I think what you’re missing is that the AVERAGE temperature of the air in the ‘fridge is going to track pretty well with the beer temp, though a few beats slow. When the beer gets warm, it warms the air. When the air gets cold, it cools the beer. The only thing that upsets that steady state equilibrium is the small amount of heat from the fermentation.

So, yeah, if you’re averaging air and liquid temps, there will be a small fudge factor. I’m guessing 0- ½ F, depending on how hot the fermentation is. I know people say that it’s 5-8F ambient, but that’s in still air, and I’m talking about a temperature probe that is in contact with the fermentor.
 
I guess we'll have to agree to disagree.

While the fudge factor is small many homebrewers are obsessed with being as accurate and precise as reasonably possible. Sticking a piece of foam on top of the probe to get a more accurate temperature is pretty reasonable. Its such a cheap and easy addition to the process that they do it even for the small increase in accuracy.
 
While the fudge factor is small many homebrewers are obsessed with being as accurate and precise as reasonably possible. Sticking a piece of foam on top of the probe to get a more accurate temperature is pretty reasonable. Its such a cheap and easy addition to the process that they do it even for the small increase in accuracy.

That’s a terrible argument. Say we are using a 62F setpoint with a 1°differential. We’re fermenting at 62.0° - 63.0° not counting overshoot. With my method, assuming twice as many cycles and a half degree offset we’re fermenting at 61.5° - 62.0° with half the overshoot. Which method is more ‘accurate and precise’?

If accuracy were important you’d use a thermowell. The problem with that method is you’re guaranteeing maximum hysteresis. If you stick the probe on the side it will cool a little faster than the beer. Thus you’ll run more frequent, shorter cycles with less overshoot.

By creative placement of the probe you can pick your duty cycle. Look at the engineering tradeoff:

You could place the probe in air for frequent small temperature adjustments. The compressor can’t do it, you would have to program a differential bigger than 1°F.

The other extreme is a thermowell, as mentioned above. The compressor kicks on and runs until the beer is cooled 1°F, but it can’t stop on a dime so there is some overshoot from the very cold air.

Wouldn’t it be fun if you could split the difference? It turns out you can.

If somebody out there wants to experiment, measure your compressor on/off times with different probe placement. Throw in thermowell temps for extra credit. The winner gets better beer.
 
You control your duty cycle with your differential setting. If you want more cycles simply change your differential to 0.5 degrees. Then you can have your temperature probe display the actual beer temperature, not somthing with a fudge factor applied to it. And I already explained above how the foam on top of the sensor is more accurate, also why the foam method has a better cost/time to benefit ratio compared to a thermowell.

I think its just a fundamental difference in what we think a control system should provide you. I would want the beer's temp displayed on my controller, not a beer air mix. Like I said before, I'll agree to disagree, this will be my last post in this thread.
 
RoadKing said:
YO! Are you copying me? Thats exactly what I do. Blue painters tape and all......LOL

I use blue painters tape and a folded paper towel. May have to upgrade to a sock....
 
I control the ambient air temp... I have a thermometer in the fermenter - I've got ambient set to 21.6c with a 0.5c hysteresis and the fermenter reads a constant 70f - maybe swinging half a degree.

Unless you have jacketed fermenters with temperature controlled chillers, throttle valves, etc, precise temperature control is tough.

I'll keep it close but I'm not going to worry about it that much.
 
Yup, me too.

The beer mass does not respond to the individual cycles of air temp, at least within context 3 to 5 degree dead band that I played with, but responds to the long term average of those cycles, indicated by a smooth decline in temp from starting to the setpoint.
 
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