# Placement Of Temp Probe = An Anal Nerd's Findings



## michael_aussie (31/10/10)

Up until now I have used a temperature probe to measure and control my ferments temperature. I have always hung my temperature in the same air space as my fermenter, not actually touching my fermenter. 

This thread inspired me to be a bit more scientific about my fermenters temperature.
*Placement Of Temp Probe For Tempmate * 
http://www.aussiehomebrewer.com/forum/inde...48876&st=20

Unfortunately, I found that I had my head in the sand. I was accurately measuring and controlling a temperature, but it wasnt the temperate of my beer. It was the temperature of the air around my beer.

I have a few STC-1000 temperature controllers, so I decided to use a few of my spares to measure additional information. What I found proved to me that I was wrong to hang it in the air. Without boring you with the individual sets of temperature readings Ill summarise what I have learnt:

1. MEASURE WHAT YOU WANT TO CONTROL. I want my beer to be a certain temperature so I now realise I need to measure my beer .. not the air near my beer, not the air in the fridge . I need to measure my beer. Im not able to measure inside my fermenter, so the next best option is a probe hard against the side of the fermenter, insulated from the air. I suspect that an immersed probe would give an even more true reading. Id be interested to hear from people who put their probe into their beer.. what readings they get there, versus on the outside of the fermenter, hard up against the side of the fermenter.

2. FREMENTATION IS AN EXOTHERMIC REACTION SO INITIALLY YOUR BEER WILL BE HOTTER THAN JUST ABOUT ANYTHING ELSE, OTHER THAN AMBIENT ON A 30+ DEGREE DAY.
I knew fermentation was exothermic, yet somehow I didnt appreciate just how much heat the beer generated. I found the beer was up to 4.3 degrees hotter than the air in the fridge with the door of the fridge closed. Harping back to point 1, therefore the only way I could use the air temperature as the control input, would be to also measure the actual beer temperature, and compensate with an offset .. and clearly this offset would need to change (decrease) as fermenting slowed, and maybe even change to compensate for changing ambient temperatures. 

3. I NEED TO GET A WORKING FERMENTING FRIDGE.
Other than in the deep of winter, the fermenter in ambient will be fermenting too hot =it took 2 days to drop from 26.2 degrees to less than 20 degrees and another 2 days to finally drop below my desired temperature of 18 degrees. Therefore, I actually need to chill my beer for at least the first 2 days to achieve 18 degrees. Clearly, this will only get worse as we enter summer.


Id love to hear about how you control your fermenters temperature, particularly, whether or not it is worth the effort (and risk of infection) of putting your probe actually into your beer.


----------



## felten (31/10/10)

Nice job, it seems only logical to me that if you want to control the temp of your beer, which fluctuates independently of the ambient as you said, that you should measure the temp of the beer itself.

I don't think you will convert any of the true nonbelievers, but if that's how they have their systems dialed in, more power to them.


----------



## geoffi (31/10/10)

Good work. Knowledge is power.

Bold use of 'anal' and 'probe' in the same thread title, btw.


----------



## Silo Ted (31/10/10)

> Nice job, it seems only logical to me that if you want to control the temp of your beer, which fluctuates independently of the ambient as you said, that you should measure the temp of the beer itself.



Makes sense, doesn't it ? I would agree with felten but having said that I am yet to install my STC1000 and christen the new fridge. What surprises me is that other thread discusses at length the ways in which not to do it like this, but instead discuss the justification in an external mount. Which begs the question, is there some theory as to why a direct suspension in the wort isn't a good idea? The only two things I can come up with is that it may deteriorate the rubber coated probe, or that brewres don't wish to drill another hole into their fermenter lid. For me it's easy, being a clingwrap convert from way back. 

Might just pop up to Ikea this morning for one of their $17 external thermo's, and mount that firstly directly in the wort for comparison (which should give identical readings, calibration permitting) and also do some comparison tests with the one probe being mounted on the outside. Its cheap enough to satisfy my interest. 

Not sure why this is a new thread when the other one was so recent but still hope this conversation can be continued, Im very interested.


----------



## felten (31/10/10)

The rubber probe isn't water proof afaik, you need some sort of thermowell for it. 

One of the big cons is that its another possible infection point.


----------



## Silo Ted (31/10/10)

Hi felten, in the case of the STC1000, the device is specifically marketed as an aquarium controller, which would suggest to me that the probe is waterproof. And if that's the case, a bath of iodofor is easy enough. Although that doesnt cover any acidic corrosion from either the wort or the sanitiser. I have two probes so am happy to test it out, and if its showing signs of corrosion, will go for plan B.


----------



## felten (31/10/10)

Sorry, I was thinking of the fridgemate rubber probe


----------



## Nick JD (31/10/10)

I suppose the other question to be raised is _when the yeast manufacturers specify a range of temperatures to brew within, are they specifying the wort temperature? Or are they taking the exothermic heat into account?_


----------



## big78sam (31/10/10)

michael_aussie said:


> Other than in the deep of winter, the fermenter in ambient will be fermenting too hot =it took 2 days to drop from 26.2 degrees to less than 20 degrees and another 2 days to finally drop below my desired temperature of 18 degrees. Therefore, I actually need to chill my beer for at least the first 2 days to achieve 18 degrees. Clearly, this will only get worse as we enter summer.
> 
> 
> Id love to hear about how you control your fermenters temperature, particularly, whether or not it is worth the effort (and risk of infection) of putting your probe actually into your beer.



As my fermentation fridge died, I just have the fermenter inside the house in a place where the temp is fairly constant. I extended the theory of lagging my BIAB urn with a sleeping bag to control temp. I have a sleeping bag wrapped around my fermenter. If fermentation is going great guns the exothermic nature tends to warm it up a bit as heat can't escape so I simply open the sleeping bag up for the 24 to 48 hours when fermentation is at its peak if I need. I either put a bottle of hot water or frozen PET under the sleeping bag if I need to adjust the temp. I find this really effective and the sleeping bag smoothes out the temperature fluctuation you'd get if it was just exposed to the open air.

I have my tempmate probe taped to the side of the fermenter. I cut out a probe sized hole into a flat piece of polystyrene and tape that to the side of the fermenter with some extra rags as insulation so the polystyrene protects the probe from ambient temps. In effect the probe touches polystyrene on one side and the fermenter on the other. I've done a number of comparisons of the tempmate reading to a sample of wort that I tap out and measure with my mash thermometer and it's within half a degree.

There's no comment on your method of making your beer, i.e. AG, partial K&K etc but my questions is, why are you pitching at 26? I'd be trying to pitch at about the temperature you want to ferment at. That way you don't need to worry about chilling for the first few days and you won't have the risk of getting undesirable flavours from fermenting too high for 2 days. If you're AGing and not using a NC cube you're clearly limited by how effective your chiller is of course.


----------



## michael_aussie (31/10/10)

Thankyou for your input so far.
I appreciate the open, non-threatening discussions we have on this forum.



felten said:


> I don't think you will convert any of the true nonbelievers, but if that's how they have their systems dialed in, more power to them.


I used to be a nonbeliever, until I measured myself and saw the light.
Others may find that the temperature differential is negligible. However, if they havent measured they wont know.



Geoffi said:


> Bold use of 'anal' and 'probe' in the same thread title, btw.


Youre a funny guy Geoffi Id like to meet you one day.
We share common interests. Beer, Southpark and pushing boundaries.



Silo Ted said:


> Might just pop up to Ikea this morning for one of their $17 external thermo's, and mount that firstly directly in the wort for comparison (which should give identical readings, calibration permitting) and also do some comparison tests with the one probe being mounted on the outside. Its cheap enough to satisfy my interest.


I would love to see your results. I will be doing the same for my next batch.



Silo Ted said:


> Not sure why this is a new thread when the other one was so recent but still hope this conversation can be continued, Im very interested.


I didnt want to hijack. However, I started the new thread to add the poll.

EDIT:- ADDED AN ANSWER TO big78sam



big78sam said:


> I have my tempmate probe taped to the side of the fermenter. I cut out a probe sized hole into a flat piece of polystyrene and tape that to the side of the fermenter with some extra rags as insulation so the polystyrene protects the probe from ambient temps. In effect the probe touches polystyrene on one side and the fermenter on the other. I've done a number of comparisons of the tempmate reading to a sample of wort that I tap out and measure with my mash thermometer and it's within half a degree.


Thankyou for your input. I was guessing that the result would be around a degree so 0.5 degrees sounds about "right".
When your fermenting fridge was a goer, did you compensate at all for this degree? That is if you wanted 18 degrees did you set your controller to 17.5 degrees knowing that the wort would be warmer?? 



big78sam said:


> There's no comment on your method of making your beer, i.e. AG, partial K&K etc but my questions is, why are you pitching at 26? I'd be trying to pitch at about the temperature you want to ferment at. That way you don't need to worry about chilling for the first few days and you won't have the risk of getting undesirable flavours from fermenting too high for 2 days. If you're AGing and not using a NC cube you're clearly limited by how effective your chiller is of course.


Im still a noob, so still K&K with a little variations.
Your question about why I pitched at 26 is a good one. I have never tried too hard to ensure the initial wort temperature was my desired fermenting temperature, because, when I was reading the air temperature, I erroneously believed that I was down to 20 within a few hours. 

I now understand that by measuring the wrong temperature (air temperature rather than wort temperature) I have been fermenting around 5 degrees higher than my desired temperature. My controller showed me 20 degrees and so I was happy. Ignorance is bliss. But now knowledge is power.
I was lead to believe that once your wort temperature was under 30 you should pitch ASAP as there was a high risk of infection at the start.
In the future I will be ensuring the wort temperature is down to my desired temperature before I pitch.


----------



## tavas (31/10/10)

I've always wondered why people measure air temp in the fridge and try to compensate for the actual temp in the fermenter. You are measuring air temp, and air is a bad conductor of heat. The problem with this method is you don't add cold to a body, you take heat away. The atmosphere around the fermenter needs to be COLDER than the temp you want to get down to. Measuring the air temp next to the fermenter will give you a colder air temp, but how this relates to the actual temp of the wort is anyone's guess, considering that fermenting wort is exothermic. It could be warmer than the air temp inside the fridge and you would never know. Opening the fridge to check on your yeasties will only exacerbate this problem.

Putting the probe into a jar of water is better, but again, how does the temp of a jar of water relate to the wort temp? You have a bigger thermal mass in the wort and its creating heat. The jar of water is smaller and has an air gap between it and the fermenter, so the temp of the water will not relate to the wort temp. All you are measuring is the temp of the water while your wort is quite happily sitting at a different temp.

If you wish to control the temp of your fermenter, you need to measure that temp. Now ideally you would place the probe in the fermenter but as mentioned that leads to a potential source of infection, and you need to ensure the probe is suited to the task. Yes you will get temp fluctuations - you are controlling around a setpoint so you can expect some hysteresys. To cool the wort you need the fridge to actually be colder than the wort, so that you get thermal transition from the fermenter to the atmosphere around it.

I doubt that ANY residential fridge would give better than 1*C control under these conditions. And anyway, how much "damage" would a 1*C swing from setpoint do the brew? Not much is my guess.

If you REALLY wanted to control your brew to exactly 18*C (or whatever temp you desire), you need to put the probe in the fermenter, and install a cooling coil into the wort so that you direct control the liquid temp.


----------



## mika (31/10/10)

I'm a hanger. In the past I've tried attaching the probe to the fermenter and haven't noticed any change in results, though I certainly haven't done this often enough to say with any conviction. I see the whole fermenting fridge as a less than ideal situation, but it's ten times better than uncontrolled fermentation. If IIRC thirstyboy also did some testing on this and I thought his conclusions were similar to yours except later in the ferment the wort did mor closely follow air temp and you didn't need to follow it that closely.
I have often wondered about stratification in the fridge and in your fermenting beer. I see huge stratification in the HLT and that's with a medium that conducts heat well. I'm sure we've all seen the YouTube videos of fermenting wort swirling around and going nuts, so perhaps in the beer stratification is less of an issue. Still, would be interesting to investigate.


----------



## yardy (31/10/10)

i shove my probe into a piece of retired stubbie holder and tape it to the fermenter, it's just one of the old adflo analogue controllers btw

Dave


----------



## Diggles (31/10/10)

I measure the wort, fitted the fermenter with a piece of tube from a keg, with a crimped end to make it water tight. The temp probe for my tempmate fits snuggly inside. Tube is easy to keep clean as it's made of stainless so there's no issues with bugs.


----------



## QldKev (31/10/10)

Good post, I agree have found the same outcome as you have from my trials. 

Also the options between
The fermenter is in a "live" fridge, with no additional heating 
and
The fermenter is in a "live" fridge, with a heater when required
may have more meaning if you know where they come from. Up here I can maintain 18 in winter inside my brew fridge (only just thou at the peak of winter) without a heater. 
Also I like the idea mentioned about the hot water bottle, if we have a really cold spell I may give that a go.

But remember which ever method you like, it will be 100 times better that sitting the fermenter in the bathroom to keep it cool.

QldKev


----------



## Silo Ted (31/10/10)

> But remember which ever method you like, it will be 100 times better that sitting the fermenter in the bathroom to keep it cool.



Exactly. Providing your pre-pitch temp is the same as your target temp, its consistency that is the key. If you always use the same gear, just compensate based on your own experience and tasting notes for the next same style brew. IMO the vast fluctuations through the process are what you want to avoid. 

By the way Michael, I did go this morning to grab that IKEA meat thermo. Dont have any beer to start fermenting, but if I rig up my STC controller today and kick the fridge into action, I might put down an easy apple juice cider tonight, and start some testing over the next few days.


----------



## bconnery (31/10/10)

Geoffi said:


> Bold use of 'anal' and 'probe' in the same thread title, btw.


Especially when in conjuction with 'placement'... h34r:


----------



## TasChris (31/10/10)

yardy said:


> i shove my probe into a piece of retired stubbie holder and tape it to the fermenter, it's just one of the old adflo analogue controllers btw
> 
> Dave


+1


----------



## MaltyHops (31/10/10)

big78sam said:


> ... but my questions is, why are you pitching at 26? I'd be trying to pitch at about the temperature you want to ferment at. That way you don't need to worry about chilling for the first few days and you won't have the risk of getting undesirable flavours from fermenting too high for 2 days. If you're AGing and not using a NC cube you're clearly limited by how effective your chiller is of course.


I have the impression (can't remember whether I read it somewhere - hold on,
the Coopers kit instructions say to pitch at 26C) that pitching at temps a little
higher than the ferment temp is good to encourage yeast reproduction at the
start.

The J.Palmer How To Brew state anything more than 10F (5C) above the nominal
ferment range and fusels (bad alcohol) start to be produced too much and I think
21C is at the top of the nominal for Coopers' yeasts, hence 26C. I'm reckoning
that providing you can get the ferment temp down to the nominal value within a
day or so after pitching at a few degrees C above the nominal would be a good
balance between getting yeast to multiply rapidly at the start and then fermenting
at the right temp for the rest of the ferment.

T.


----------



## Banshee (31/10/10)

Nick JD said:


> I suppose the other question to be raised is _when the yeast manufacturers specify a range of temperatures to brew within, are they specifying the wort temperature? Or are they taking the exothermic heat into account?_



Good point. I set and forget. I also use an analouge thermostat and not a digital tempurature controller.
I would like to see a parabola on heat produced and retained in regards to fermenter volume and shape.
Wouldn't a tall skinny vessel loss heat faster than a short stubbie vessel.
More research to be done.


----------



## juzz1981 (31/10/10)

I dont have any temp sensor on my fermenter, i just shoot it with a IR gun


----------



## felten (31/10/10)

You're right, yeast rehydrate better at higher temps, but higher temps aren't good for flavour development. That is why usually you are advised to rehydrate the yeast in hotter water before pitching into your beer. 

Starting the beer off lower and then letting it ramp up towards the end is a lot better solution





MaltyHops said:


> I have the impression (can't remember whether I read it somewhere - hold on,
> the Coopers kit instructions say to pitch at 26C) that pitching at temps a little
> higher than the ferment temp is good to encourage yeast reproduction at the
> start.
> ...


----------



## Nick JD (31/10/10)

The Activator™ package contains a minimum of 100 billion cells in a yeast slurry.. The Activator™ is designed to directly inoculate 5 gallons of standard strength ale wort (1.034-1.060 SG) with professional pitching rates. For lagers, we recommend inoculating the wort at warm temperatures (68-70F/ 20-21C), waiting for signs of fermentation, and then adjusting to the desired temperature. Alternatively, for pitching into cold conditions (34-58F/ 1-14C) or higher gravity wort, we recommend increasing this pitching rate. This can be achieved by pitching additional Activator™ packages or by making a starter culture. Please see the Pitch Rate section for additional information. *Instructions for the proper use of Activator™ packages:*


To activate, locate and move inner packet to a corner. Place this area in palm of one hand and firmly smack package with the other hand to break inner nutrient packet. Confirm inner packet is broken.
Shake the package well to release the nutrients.
Allow package to incubate and swell for three hours or more at 70-75F (21-24C) or immediately direct pitch into wort.
Use sanitizing solution to sanitize the package before opening.
Shake well, open and pour Activator™ into five gallons of well-aerated or oxygenated wort at 70-75F (21-24C). Maintain temperature until fermentation is evident: by CO2 bubble formation, bubbling airlock or foaming on top of wort.
Adjust to desired fermentation temperature.

21-24C wort temp folks (20-21C for a lager). Yeasties won't spit the dummy till they're multiplied up and shittin' alcohols. I always pitch my lager yeasts at 20C. Bring it down to the temperatures you get your best results from afterwards. Personally I think there's a fine line between happy yeast and rampant fusel/ester production with most yeasts. Finding this line is almost as important as freaking out about your anal probe.


----------



## Silo Ted (31/10/10)

> You're right, yeast rehydrate better at higher temps, but higher temps aren't good for flavour development.



Once again I agree with you felten. To extend on your comment, and for the benefit of newer brewers-higher temps might be good for yeast reproduction, but once it hits the wort a brewers main 
interest is in making beer, not more yeast. For stepping up a yeast sample, room temp is fine with me. But when it comes to pitching its probably a good idea to have your starter at a similar temp to the receiving wort.


----------



## gregs (31/10/10)

This is a good topic 
An interesting point made regarding the fermentation temperature to aid yeast multiplication before lowering the temperature to the correct fermenting temp. 

I wonder when fermenting larger volumes re 60 litres, how long will it take that batch size to drop from 21 degrees to the desired 11 degrees when using lager yeast. This would take some time I would presume, especially if placing the temp probe in the actual wort.

I have always for this reason pitched my yeast when the wort is at the recommended fermentation temp.


----------



## razz (31/10/10)

Probably a good point with larger batches gregs, I'm doing 40 lt brews and I pitch at fermenting temps. Keeping the fermenter in a fridge, if I pitched at 18 and tried to take the fermenter to 12 degrees I would wait for approx 16-24 hours and the fridge may not like running non stop.


----------



## big78sam (31/10/10)

Silo Ted said:


> Once again I agree with you felten. To extend on your comment, and for the benefit of newer brewers-higher temps might be good for yeast reproduction, but once it hits the wort a brewers main
> interest is in making beer, not more yeast. For stepping up a yeast sample, room temp is fine with me. But when it comes to pitching its probably a good idea to have your starter at a similar temp to the receiving wort.




+1

A side point - A bit of forethought means the K&K brewer can fairly easily ensure the wort is at the desired temp so there's no need to cool down or warm up. I'm no maths/chemistry whiz but in my K&K days I used some basic maths to work out how much boiling water I should use to get the final wort temp about right.

For example, assume a final volume of 22 litres. 
20 litres of water at 15 degrees (or whatever your tap water is assuming you're using this to top up)
2 litres water at 90 degrees (assuming it cools a bit)

I leave the tins and adjuncts out of the equation as I assume they are about room temp.

(20x15 + 2x90) / (20 + 2) = 21.8

21.8 degrees is about right. So I'd use 2 litres of boiling water when mixing tins etc up. You'll have to work out specifics yourself but it was just a rough rule of thumb that seemed to work for me.

http://www.scienceforums.net/topic/16788-c...er-temperature/ This is a better but brief explanation of how it works.


----------



## Silo Ted (31/10/10)

Sam - that's a handy reference, and for those who need to change temps quickly its ideal. Those who are uncomfortable with using math formulae, but still want to think about forcing pitch temps and play around with mixing solutions for a desired temp (it works both ways) might like to bookmark this calculator. 

http://www.onlineconversion.com/mixing_water.htm

Try it out with Sam's example, the results are the same. 

Keep in mind that you might need to compensate your gravity predictions for the addition of plain water. For example, an initial 21L wort at 1.050 OG would drop to 1.046 after a 2L water addition. An extra 250g of dry malt (or sugar, or dex) would bring it back up.


----------



## big78sam (31/10/10)

Silo Ted said:


> Sam - that's a handy reference, and for those who need to change temps quickly its ideal. Those who are uncomfortable with using math formulae, but still want to think about forcing pitch temps and play around with mixing solutions for a desired temp (it works both ways) might like to bookmark this calculator.
> 
> http://www.onlineconversion.com/mixing_water.htm
> 
> ...




That's a much easier way of doing it. I think I'll bookmark that and use that instead of using a calculator or trying to do it in my head!


----------



## Silo Ted (31/10/10)

Sorry to Michael if this is getting a bit off topic, but in a way its all tied in together with temperature control, and the best way to produce a pre-pitching temp. 

Apologies out of the way, let's get seriously OT  Sam, I wonder if the weight of wort per litre is significantly variable to the assumed weight/volume of water, enough to alter the mixing calculation by a couple of degrees? Your stated formulae, and the corresponding equal result from the online calc, are assuming the solutions to be water, not a sugary solution.


----------



## michael_aussie (31/10/10)

Thankyou everyone .. some interesting thoughts.



big78sam said:


> For example, assume a final volume of 22 litres.
> 20 litres of water at 15 degrees (or whatever your tap water is assuming you're using this to top up)
> 2 litres water at 90 degrees (assuming it cools a bit)
> 
> ...


ty again big78sam.
I'm going to be more scientific about my wort temp, but can't use just 2 litres of water; I always seem to need at least twice that to dissolve the solids.
I'm going to try adding some ice to counteract the extra heat I introduce with extra hot water.

Therefore SiloTeds link is even more useful as it also allows you to input ICE.
Thank you SiloTed ... I don't mind wandering topics ... it all adds to my knowledge. I always appreciate your input.



Silo Ted said:


> Sam - that's a handy reference, and for those who need to change temps quickly its ideal. Those who are uncomfortable with using math formulae, but still want to think about forcing pitch temps and play around with mixing solutions for a desired temp (it works both ways) might like to bookmark this calculator.
> 
> http://www.onlineconversion.com/mixing_water.htm


----------



## michael_aussie (31/10/10)

Silo Ted said:


> http://www.onlineconversion.com/mixing_water.htm


Using Silo_Ted's link, I need 2 x 1.25PET bottles of ice in my wort.


----------



## big78sam (31/10/10)

michael_aussie said:


> Using Silo_Ted's link, I need 2 x 1.25PET bottles of ice in my wort.


 Not sure what you mean by that - how do you intend to use PET bottles? I assume just mean 2.5 litres of ice.

The other option is to use 4 litres of boiling water, add tins of goop, hops, LDME etc, and then cool this to around 40 or 50 degrees and finally add the rest tap water. It's much quicker and easier to cool 4 litres of near boiling liquid to around 50 than it is to cool 23 litres of wort. I'd do this by boiling water etc in a pot and then leaving the pot in a sink full of cold water.


----------



## big78sam (31/10/10)

Silo Ted said:


> Apologies out of the way, let's get seriously OT  Sam, I wonder if the weight of wort per litre is significantly variable to the assumed weight/volume of water, enough to alter the mixing calculation by a couple of degrees? Your stated formulae, and the corresponding equal result from the online calc, are assuming the solutions to be water, not a sugary solution.




I don't know about that. This was just a rough rule of thumb for me. The formula mentioned in the thread I posted talked about mass and specific heat capacity. I wouldn't have thought the sugar content would make much difference to mass. My understanding is the SG is in effect the ratio off the mass of a volume of liquid to pure water. In other words 1 litre of wort at 1.050 SG weighs 1050 grams or 5% heavier than 1 litre water, so we're not talking about enormous amounts of difference here. I have no idea about specific heat capacity though.

In any event, my non scientist mind figured that the sugar sourced from the tins, LDME etc could be excluded as the temperature is really determined by the water you're adding due to the much larger volumes of water. For example if you added the boiling water and the tap water and then end up with say 23 litres at 20 degrees and then added the extras the temp isn't going to change much. Common sense would tell me that the order in which you combine the ingredients shouldn't matter, i.e adding the boiling water to the tins etc, then adding tap water last should give the same result as combining the water first. I have no scientific basis for this.


----------



## Silo Ted (31/10/10)

LOL you said what I was thinking. Does he cut the bottle off the ice ? 

Michael, if youre getting into this solution mixing conversion concept, are you sure your tap water is 15 degrees? Not being in the same climate as you, but I just went and measured my tap water and it's 23 degrees. Also just checked my loungeroom Galileo Thermometer (imprecise functional art) and it's around 24 degrees. 

This is a good sidestep discussion, and I reckon more people should be thinking about controlling their pre-pitching temps with mixing. To extend on Sam's last one, work out the least amount of boiling water you need to dissolve the LME, DME, whatever, and then dunk your saucepan into cold tap water. After about five minutes, drain the water, and do it again, leaving for 10 minutes. Then a third time for 15 minutes. Leave the lid on the whole time, apart from in between baths, where you might want to stir it with a spoon so get some currents going. You'll be surprised how much heat will dissipate, so when you tip the high SG solution into your fermenter, and top up with tap water, there's no 90 degree factor to push the overall readings up.


----------



## Silo Ted (31/10/10)

> I don't know about that. This was just a rough rule of thumb for me. The formula mentioned in the thread I posted talked about mass and specific heat capacity. I wouldn't have thought the sugar content would make much difference to mass.



Probably not enough to worry about, but I suspect there is a variance in weight between a volume of water and a volume of wort. It was more in the spirit of the discussion rather than for any practical application. Since posting that, I'm starting to wander off into heat dissipation variances of water vs wort. God help me, this hobby gets the old grey matter working  



> I have no scientific basis for this.



Off topic again (sorry Michael). A mate of mine came up with a funny statement about brewers, in that many have failed basic high school chemistry, but own hydrometers, refractometers, pH readers, build our own stir plate circuits to propagate micro-organisms, discuss water alkalinity profiles, have a range of thermos for various applications, work out attenuation figures, manipulate temperatures for ester production and all manner of other scientific applications.


----------



## Ross (1/11/10)

razz said:


> Probably a good point with larger batches gregs, I'm doing 40 lt brews and I pitch at fermenting temps. Keeping the fermenter in a fridge, if I pitched at 18 and tried to take the fermenter to 12 degrees I would wait for approx 16-24 hours and the fridge may not like running non stop.



Razz,

Don't worry about over running your fridge, the fridge thermostat is not disconnected & will run as per normal, all that happens with your controller is that it turns the whole fridge off once fermentation temperature is reached.

cheers Ross


----------



## piraterum (1/11/10)

yardy said:


> i shove my probe into a piece of retired stubbie holder and tape it to the fermenter, it's just one of the old adflo analogue controllers btw
> 
> Dave




The idea of wrapping the temp probe with an insulator defies logic :blink: 
This would effectively insulate the probe against temp change. You would have to wrap the whole fermenter in insulation the same as the probe, for this to be a viable option.

The most accurate way to measure the temp would to have a probe directly inserted into the wort. Preferably inserted between the the middle of the fermenter and the surface of the wort to account for the variation of temperature within the fermenter. The wort near the surface will be cooler than the wort in the middle. A quick google search can provide plenty of info on this:

Emerson Process management

Yokogawa proccess doc


Anyone have any pics of how they fitted a probe with a neat seal?

cheers,

piraterum


----------



## Thirsty Boy (1/11/10)

You have misinterpreted the insulation of the probe method.

You put the probe directly onto the surface of the fermenter, and tape the insulation on so that its between the probe and the ambient air. Insulating it from the inside temperature of the fridge and making it read what is for all intents and purposes, the internal temperate of the wort.

The test have been done and described enough times over the years by various people, one of whom is me, that show the temperature measured via an immersed probe is usually not significantly different (ie less than one degree) to the temperature measured by an insulated, probe taped to the outside of the kettle.


----------



## MarkBastard (1/11/10)

Thirsty Boy said:


> You have misinterpreted the insulation of the probe method.



I think he may be suggesting that insulating the probe in this way would mean that as the ambient gets colder than the liquid, the insulation will block that ambient cold air from hitting the wort behind where the probe is, and thus the probe will not be accurate.

I disagree and I think this is actually a positive benefit.

I imagine when you want your wort to be 18 degrees and the fridge gets the ambient air down to say 14 degrees, the edges of the wort get colder first, with the middle remaining warmer. With that in mind the area on the edge of the fermenter that is insulated may read a closer temperature to what the middle of the fermenter would be, so it's a good thing.

Either way this is all theory. In insulate using some leftover camping mat and I have zero cause to ever change this. It's just too easy.

My only concern is that my temp controller is only accurate to one degrees so the wort temperature itself needs to change a fair bit for the fridge to turn on.

Ideally the temp controller would have a greater accuracy but I'd use the same method.


----------



## sinkas (1/11/10)

Anal Nerd?, wrong forum dude.....


----------



## SpillsMostOfIt (1/11/10)

tavas said:


> I've always wondered why people measure air temp in the fridge and try to compensate for the actual temp in the fermenter. You are measuring air temp, and air is a bad conductor of heat. The problem with this method is you don't add cold to a body, you take heat away. The atmosphere around the fermenter needs to be COLDER than the temp you want to get down to. Measuring the air temp next to the fermenter will give you a colder air temp, but how this relates to the actual temp of the wort is anyone's guess, considering that fermenting wort is exothermic. It could be warmer than the air temp inside the fridge and you would never know. Opening the fridge to check on your yeasties will only exacerbate this problem.



... etc. I've snipped to conserve your electrons...

I agree with this almost entirely. However, I have my probe measuring the temperature of the air inside the fridge - or a side panel of the cabinet.

You can happily and correctly assert that you want to know the temperature of the beer as it ferments. I won't argue with that.

I will argue that if you put your probe into a vessel of liquid, what you are effectively doing is going into the controller's setup and increasing the hysteresis.

My base position is that none of it matters, unless you want it to. (And there is nothing wrong with that!)

I've come around to the position where I want to know 'a number' at which good beer results for any given set of other numbers (yeast strain, OG, etc.). I tend to use a quite small number of yeast types and try to make my process the same across batches (ignoring the Shepherds Flat Brewery's Continual Improvement Policy). After *cough* 'enough' *cough* experimentation, I know that when I set the temperature controller so that it maintains a temperature of X+/-Y degrees Celsius, the beer turns out the way I think I want. And that is good enough for me.

Good work on the part of the OP. If it helps you get where you're going, even better.


----------



## Brewindo (1/11/10)

Please correct me if I am wrong.

I put the temp probe of my digital controller "next to the fementer, within 2" in the air".

Why? Even with the probe in the air, I have noticed that when the fridge cyles "on" and reaches the set point temp (say 18deg), the fridge cuts out. However the temp continues to fall. This is like a sort of thermal acceleration, as the fridge was working to get to a low temp but the controller interviened at 18deg. So the residual cooling effect is continuing to cool the cabinet beyond where the temp is set. Gets down to arround 16.5deg then slowly starts climbing back up.
With this cycling effect, I guess that the resultant average temp of the fermenter would be somewhere between 17 - 17.5deg.

Alternativley, if I was to imerse the probe dirrectly in the fermenter, I would imagine that this would just increase the effect of what I described above. The ambient air temp inside the fridge would get much lower before the "core" of the fermenter was reduced to the desired temp.

Anyone done any testing with this in mind? I'm not a scientist but this is my thinking.

:icon_chickcheers:


----------



## mika (1/11/10)

Have noticed this effect as well and it resulted in my fridge with newly included heating source 'bounce'.
I haven't got round to figuring it out yet, so I simply increased the differential temp to solve it for the moment.
Be interesting to know whether having the probe connected to the fermenter would solve this.


----------



## Nick JD (1/11/10)

I'd say as long as you can hold temperature within a 3 degrees C range you won't be making beer that tastes any different to that held to within a 0.1C range.


----------



## Banshee (1/11/10)

Yesturday after reading yet another where do you place your probe question I got my two digital thermometers out and put one in the wort and the other in placed on the fermenter lid exposed to the air. Both meters are reading 13C. Tempurature outside of the fridge is 40C.
So for me I don't bother placing it in my fermenter as long as it is in a constant surrounding tempurature I dont' give two hoots what the temp of my fermenting wort is as long as it is in a controled enviroment and it tastes good in the end.
Relax and have a homebrew.


----------



## Brewindo (1/11/10)

Banshee said:


> Yesturday after reading yet another where do you place your probe question I got my two digital thermometers out and put one in the wort and the other in placed on the fermenter lid exposed to the air. Both meters are reading 13C. Tempurature outside of the fridge is 40C.
> So for me I don't bother placing it in my fermenter as long as it is in a constant surrounding tempurature I dont' give two hoots what the temp of my fermenting wort is as long as it is in a controled enviroment and it tastes good in the end.
> Relax and have a homebrew.




Thank you... I will worry no more. Your point is loud and clear. I will leave my probe outside my fermenter and poor a cool one. :kooi:


----------



## wessmith (1/11/10)

Try Bluetack to hold the probe on to the fermenter wall. It works a treat.

Wes


----------



## argon (1/11/10)

yardy said:


> i shove my probe into a piece of retired stubbie holder and tape it to the fermenter, it's just one of the old adflo analogue controllers btw
> 
> Dave



Exactly what i do... beers turn out fine... i have found that the air temp it slightly below that of the fermenter. Not sure if this really matters though.


----------



## Mutton Chops (4/11/10)

Brewindo said:


> Please correct me if I am wrong.
> 
> I put the temp probe of my digital controller "next to the fementer, within 2" in the air".
> 
> ...




To control that bounce you would need to start looking at PID control (or if possible adjusting your deadband setting) but I would have thought that with a well insulated fridge On/Off control would be sufficient, or does the fermenation generate that much heat?

Being new to the process I will definitely have temp control down the track and would be interested to know (depending on ambient temps) how hard the old fridge cycles to maintain brewers desired set point using the On/Off control method and what kind of error across the various conditions.

Cheers


----------

