# Fermentation Temperature Vs Fridgemate



## clean brewer (29/10/09)

Hey,

After receiving some feedback from QABC in relation to some beers, a couple comments were made in relation to controlling my Fermentation? :unsure: I thought I did....

Anyhow, I have the probe for my Fridgemate attached to the side of the fermenter with a big wad of Blue Tack, now taking into consideration the temperature of the Fermenter(heat from fermentation)and the Ambient Temp of the fridge, could I be right in saying that if my Fridgemate is set to 18 degrees, the temp of the Wort/Beer could actually be higher????

A quote from Butters in another Topic...


> Fermentation is an exothermic process, ie it creates it's own heat. So the actual wort temp will always be higher than the ambient temp, whilst fermentation is active.
> 
> edit: the specific temperature difference varies based on too many factors to worry about on a HB level; suffice it to say that it's usually ~ 2-3C difference. YMMV.



Should I maybe set the Fridgemate to 16 degrees for the Bulk of Fermentation and then raise to 18 degrees for the rest????

Obviously with the probe stuck to the side of the fermenter, its not giving an accurate reading of the core of the Wort???

:icon_cheers: CB


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## glaab (29/10/09)

I cut in half a wet suit stubbie holder and tape it to the side of the fermenter with the probe under it,
it's about 1 degree out at worst compared to a probe in the middle of the wort, close enough for me. Sanitize your probe and drop it in you'll soon find out the diff.
If your at 18 - 20 that sounds pretty good, 20 might be better depending on what your brewing and your type of yeasties. :icon_cheers:


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## dpadden (29/10/09)

Hey CB, have you calibrated the fridgemate against something a little more reliable? Be interesting to know how reliable it is


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## Thirsty Boy (29/10/09)

IMHO - the temperature differnece between the wort and the side of teh fermenter is minimal. I did a few experiments where I measured wort temp with a thermometer inserted in the wort vs temperature read through the sides of the fermeter. They were always within 1C of each other - and thats inside the accuracy of my temp controller. Mind you, this is with a bare thermocouple sensor, not a chunky fridgemate probe.

Two things though - I always, tape the sensor onto the fermenter and then cover the probe with a double thick insulating square of camping mat. This shields the probe from the ambient temp in the fridge. I dont think a lump of blu-tack is a very good insulator.

Second - I don't think that when you are controlling the temp via turning the fridge on and off - that having the probe attached to the fermenter is the best place. Your fridgemate has a swing built in, you probably have it set to 1C?? So if the probe is stick to the fermenter, the fridge is slaved t the wort temp and therefore the wort temp must swing by the amount built into the fridgemate. Now on cooling... with a 1C diff set, the fridgemate will drop your wort to 1C below your set temp and then turn off... then it will let it warm up to 2C above the set temp before it kicks the fridge back in. so with a set temp of 18C ... your wort is actually being _driven_ between 17 & 20 in a wave pattern. And swinging temp is bad for fermentation.

Now if you have the probe measuring ambient - its the temperature in the fridge that swings wildly... the wort temperature is much more stable. It might vary slightly, but nothing like it would with the fridgemate actually forcing it up and down. All you need to do, is stick on a bog standard HB temperature strip... set your fridge temp and see what the fermeter temp ends up at. Then you can calibrate the fridgemate so that the set temp reflects the average temp of the fermenting beer. I'd do the test with water, but as mentioned, the beer will probably be a little hotter during active fermentation.. so you might need to adjust the temp down a degree or so and put it back up once fermentation starts to slow down.

Thats the way I see it anyway, which is one of the reasons I dont control my temperatures like that - but I use PIDS and heaters and you dont need to hear about that. think moving your probe to measuring the fridge temp would give you much more stable fermentation temperatures. I'm sure others will have differing opinions.

Thirsty


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## clean brewer (29/10/09)

Paddo said:


> Hey CB, have you calibrated the fridgemate against something a little more reliable? Be interesting to know how reliable it is



Ill do that this afternoon....


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## BjornJ (29/10/09)

Thirsty Boy said:


> Two things though - I always, tape the sensor onto the fermenter and then cover the probe with a double thick insulating square of camping mat. This shields the probe from the ambient temp in the fridge. I dont think a lump of blu-tack is a very good insulator.
> 
> Second - I don't think that when you are controlling the temp via turning the fridge on and off - that having the probe attached to the fermenter is the best place. Your fridgemate has a swing built in, you probably have it set to 1C?? So if the probe is stick to the fermenter, the fridge is slaved t the wort temp and therefore the wort temp must swing by the amount built into the fridgemate. Now on cooling... with a 1C diff set, the fridgemate will drop your wort to 1C below your set temp and then turn off... then it will let it warm up to 2C above the set temp before it kicks the fridge back in. so with a set temp of 18C ... your wort is actually being _driven_ between 17 & 20 in a wave pattern. And swinging temp is bad for fermentation.
> 
> Now if you have the probe measuring ambient - its the temperature in the fridge that swings wildly... the wort temperature is much more stable. It might vary slightly, but nothing like itwould with the fridgemate actually forcing it up and down. Thirsty



Brillaint timing!
Put my fridgemate together today and have now plugged the fridge in with a cube of tap water in it to simulate (!) the fermenter with the probe just taped on to it to test the fridgemate.
I have read with interest about this discussion before and never having tried it, two arguments both seem to make sense.

1: Bluetack to the side of the fermenter (or a more insulating material).
The temperature is measured on the wort which is what we care about, not the ambient air temp. When the fermentation kicks off and the wort temp goes up, the fridge will cut in "earlier" to control the temperature. Sounds clever.

2: Leave the probe hanging in the air.
Measuring the ambient air temperature of the fridge rather than the wort temperature makes great sense! As soon as the air temperature drops by a degree, the fridgemate will kick in, long before the wort temperature has dropped "by much". So the fridgemate controls the air temperature, leaving the wort temperature much more constant than if the temperature would be controlled by the wort temperature.

But I can't do both!  

Side of the fermenter seems to cycle the entire wort temperature 17-19 degrees = bad?
Air temperature does not control the wort when fermentation increases temperature = bad?
Side of the fermenter can take into consideration the heat from fermentation = good
Air temperature measuring keeps wort temperature more constant = GOOD


Thirsty Boy seem to know how this works, but should we measure in the air or in the fermenter? The post above says that you do it on the fermenter, then the next point says in the air so I'm a bit confused (and haven't even had a beer yet, hehehe)

thanks
Bjorn


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## niggles (29/10/09)

Yep, +1 to Thirsty Boy's input. 

Check out a post I did a while back [post="411990"]here[/post]. 

I stick the controlling probe to a glass of water sitting next to the fermenter. Depending on fermentation activity, I've measured the temp in the beer to be ~1-1.5C higher than at the probe, so adjust the set point to suit. The difference between the beer and the side of the fermenter will be slightly lower, but I've found overshoot and long cycling less of an issue with the probe separated from the fermenter.


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## clean brewer (29/10/09)

niggles said:


> Yep, +1 to Thirsty Boy's input.
> 
> Check out a post I did a while back [post="411990"]here[/post].
> 
> I stick the controlling probe to a glass of water sitting next to the fermenter. Depending on fermentation activity, I've measured the temp in the beer to be ~1-1.5C higher than at the probe, so adjust the set point to suit. The difference between the beer and the side of the fermenter will be slightly lower, but I've found overshoot and long cycling less of an issue with the probe separated from the fermenter.


Cheers guys, this info is what im after and maybe why I have comments about my fermentation, its changing to much...  

:icon_cheers: CB


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## Screwtop (29/10/09)

Some findings of mine re fermentation control using fridgemates. Took a few stalled ferments before I began to become suspicious about what temp my wort was being maintained at in my fridges. Using a few finickety yeast strains I had ferments stall, after taking the temp of the wort using a quality thermometer I found that the wort was lower in temp than the Fridgemate setting by a couple of degrees and sometimes as much as 3.

The second time I dropped a beer to 1C after fermentation I left it for three days and then removed the fermenter to rack to keg and found the beer was frozen in the centre, the outer part was unfrozen. The beer was around 5% ABV and so should not have frozen at 0. Obviously there was some sort of overrun causing the problem, the probe taped on the side of the fermenter at mid wort depth with some foam insulation covering the probe. Had some thoughts that maybe the air/plastic fermenter wall interface has a greater transfer rate than the liquid and so the core of the liquid was amassing lower temps as the outer part near the fermenter wall warmed and the fridge switched on and again chilled the air in the cabinet. 

Basically now I add 2 to all of my temps, so for fermenting at 18 the fridgemate is set at 20 and to drop out yeast at 1 the setting is 3C. Seems to work nicely using my fermentation fridge. 

This may depend upon the size and/or efficiency of different fermenting fridges.

Screwy


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## shonks69 (30/10/09)

Hi all

I have recently set up a fermentation fridge using a sopac air-con thermostat to control my fermenting temp and use the original fridge thermostat to chill the wort via toggle switch (The sopac thermostat measures the air temp of the fridge). I also fitted an electronic aquarium thermometer to the fridge with its probe immersed in glycol measuring the temp inside the fridge, my fermenter also has a stick on thermometer on it.
I have now tried three brews in the fridge and all have stalled approx 4 days into fermentation at approx SG 1020. I have been targeting 18 deg fermentation temps using SAF-04 yeast and have maintained this temp with in +/- 1 deg. 
I the pitch the yeast at 24 deg and leave fridge turned off until fermentation has started (overnight), I then drop the fermentation temp to 18 deg in the fridge (fermenter stick on thermometer colored scale reads a color gradation from 18 - 22 deg).
How accurate are the fermenter stick on thermometers and which gradation of the color scale is the actual temp? 

Cheers
Shonks :icon_cheers:


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## MarkBastard (30/10/09)

Thirsty Boy, that's why I like to stick the probe to the side of the fermenter with minimal insulation outside it.

That way it's measuring both the wort temperature AND the fridge temperature, and giving you something in between.

For example when I have my wort at 30 degrees or so and I haven't pitched yeast yet due to needing the fridge to cool the wort down first, the probe measures 30 degrees, even without insulation (I've tested this). But it does seem to cycle more and not let the wort temp drop down or go up before cutting in. It seems to be the perfect in between. I just use a bit of cardboard as insulation basically.

You're right though, I wouldn't control a fermenting fridge on wort temperature unless my thermostat had 0.1 degrees precision.


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## King Brown (30/10/09)

If the fridge has reasonably efficient insulation on it and you dont open it too often wouldnt the temp swing be fairly minimal?


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## QldKev (30/10/09)

King Brown said:


> If the fridge has reasonably efficient insulation on it and you dont open it too often wouldnt the temp swing be fairly minimal?



The problem is if the fridge controller is set to come on at 17 and turn off at 20, even with the best insulation your fridge will eventually heat until the 20, thermostat kicks in and drops the beer temp to 17 before kicking out. 

Better fridge insulation will mean this just doesn't happen as often, but will still happen.

QldKev


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## technocat (30/10/09)

clean brewer said:


> Obviously with the probe stuck to the side of the fermenter, its not giving an accurate reading of the core of the Wort???



It won't, I have tried this and it gives an erroneous temperature to actual temps in the centre of the liquid being monitored. I found a thermowell in the centre of the liquid not withstanding layering differences was the only reliable way of monitoring near true temps.

cheers


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## Thirsty Boy (31/10/09)

See, beernut finds this phenomenon to be exactly the opposite from me and some others.. but I bet he has a few people who agree with him too - this is why this is such a hard question/topic. I'm pretty sure that so far there has been a "this is the way to do it" AND a "what ever you do, don't do it this way..." for most of the permutations.

Its unfortunately one of those areas where you will just have to try a few different options and combine that with your idea of which brewer's argument makes the most "sense" to you. Basically you will be able to find _someone_ who is making any and/or all of the different options work for them.


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## clean brewer (31/10/09)

Ive now put a Jar full of water in my ferment fridge with the Probe attached to it, my Digital thermometer is reading 18 degrees at the moment as does the Temp gauge on the side of the Fermenter, fridgemate is set to 16 degrees... The wort temp should stay stable this way as the Fridgemate will only have to run to get the Jar of Water down to temp, not 23 litres of wort....

I think this will work much better...  

Cheers for all your input guys, this is what I love about the Forum, so much advice and so many different ways, just gotta work out what works the best for you.....

:icon_chickcheers: CB


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## schooey (31/10/09)

Screwtop said:


> Some findings of mine re fermentation control using fridgemates. Took a few stalled ferments before I began to become suspicious about what temp my wort was being maintained at in my fridges. Using a few finickety yeast strains I had ferments stall, after taking the temp of the wort using a quality thermometer I found that the wort was lower in temp than the Fridgemate setting by a couple of degrees and sometimes as much as 3.
> 
> The second time I dropped a beer to 1C after fermentation I left it for three days and then removed the fermenter to rack to keg and found the beer was frozen in the centre, the outer part was unfrozen. The beer was around 5% ABV and so should not have frozen at 0. Obviously there was some sort of overrun causing the problem, the probe taped on the side of the fermenter at mid wort depth with some foam insulation covering the probe. Had some thoughts that maybe the air/plastic fermenter wall interface has a greater transfer rate than the liquid and so the core of the liquid was amassing lower temps as the outer part near the fermenter wall warmed and the fridge switched on and again chilled the air in the cabinet.
> 
> ...



Probably a silly question, but have you ever calibrated your Fridgemate against your 'good quality' thermometer, Screwy, to see what the digital readout says against the actual temp in a glass of water?


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## dicko (31/10/09)

schooey said:


> Probably a silly question, but have you ever calibrated your Fridgemate against your 'good quality' thermometer, Screwy, to see what the digital readout says against the actual temp in a glass of water?



Mmmm!

I have recently found a Fridgemate to be 5 deg c out compared to a Digi Therm thermometer which is used to check fridge and air cond temps in the industry.
I re calibrated the Fridgemate over a period of a week with the unit controlling the temp of a small chest freezer by using the Digi Therm as the standard and now that set up is working just fine.
So; dont just rely on the controller to be the correct temp out of the box.

Cheers


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## clean brewer (31/10/09)

Paddo said:


> Hey CB, have you calibrated the fridgemate against something a little more reliable? Be interesting to know how reliable it is


Paddo, yes I have just checked it yesterday and its spot on correct... So not a issue there...  

:icon_cheers: CB


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## Screwtop (31/10/09)

schooey said:


> Probably a silly question, but have you ever calibrated your Fridgemate against your 'good quality' thermometer, Screwy, to see what the digital readout says against the actual temp in a glass of water?




Four years ago I probably would have been so anal as to to that. Now I basically use results as my yardstick, if a beer tastes like fermentation was too warm I make a note in the recipe to wind back the temp a little on the next batch, or if the yeast drops early the opposite.

Screwy


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## Brewman_ (1/11/09)

Hi,
This is a challenging question. There are lots of opinoins and there are differnet controllers.

Theoretically I agree with beernut in a way. You have to try to measure what you are trying to control. So measure the beer itself or something in the fridge like the beer - a liquid. I beleive that you need a complex, PID, controller to do this effectively, and do you really need it? Is +- 1 or 2 Degrees too much variance? This is ideal.

Thirsty boy's method is probably a good practical solution. Is it exact, - No. Is it close, yes, and as mentioned by some other posters if you validate your controller against another thermometer, you can be sure your temperature is approximately correct.

Just my opinoin.

Fear_n_Loath


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## browndog (1/11/09)

fear_n_loath said:


> Hi,
> This is a challenging question. There are lots of opinoins and there are differnet controllers.
> 
> Theoretically I agree with beernut in a way. You have to try to measure what you are trying to control. So measure the beer itself or something in the fridge like the beer - a liquid. I beleive that you need a complex, PID, controller to do this effectively, and do you really need it? Is +- 1 or 2 Degrees too much variance? This is ideal.
> ...



You can't use a PID for a frigde or you will kill it quickly, frdges are meant to be either off or on, not supplied a percentage of that power as a PID would try to do if it had a cooling mode.

cheers

Browndog


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## Brewman_ (1/11/09)

Hi Browndog,
Thanks for the clarifation, forget the theory - it is not possible with a fridge then.

It just means that there are some limits to control for the average Home Brewer. This is not a real issue IMHO, so will leave it there. 

Fear_n_Loath


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## Diggles (1/11/09)

My setup is slightly different, I've inserted an old dip tube from a keg into the wort after crimping the tube's end to seal it. The probe supplied with the tempmate fits nice and snugly into the tube. Used a rubber grommet around the tube to seal it through the fermentor lid and hey presto!

Have double checked the temp in the fridge (air) with another cheaper thermometer and both looked to be tracking eachother, with a little lag time as you'd expect.

I figure, you need to be measuring the thing you're attempting to control...the wort. :icon_drunk:


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## Thirsty Boy (1/11/09)

Mildly OT - 

You can't use PID with a fridge if you are controlling the fridge itself -- doesn't mean you cant use a PID. I ferment in an uncontrolled fridge set to about 5 or 6 degrees (fridgemate) and control my fermentation temperatures with a heater immersed in the fermenter, the heater is driven by a PID. Insulation on the fermenter keeps the heat transfer rate low and the fridge runs only about 10-20% more frequently than "normal" operation when fermenting an ale, less with a lager.

Solves all the problems - I get to measure and control via the wort temperature (through the side of the fermenter), but because I am using a PID rather than an on/off controller, I get accuracy to one degree with basically no swing. Plus I get to cold crash/lager beer in the same fridge, use it as a secondary keggerator, store my yeast and bottled beer in there and my hops in the still functional freezer ... all at the same time as I am fermenting at anywhere from 9-22ish.

Me - I dislike limits to my levels of control. I want to be able to control every temperature in my whole brewing process, accurately, to within less than 1C. Anything else is guessing as far as I am concerned.


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## O-beer-wan-kenobi (27/9/13)

I use a fridgemate and was thinking about this same issue which led me to this thread.

I fix my probe to the side of the fermenter and cover with insulation. But as the posts in this thread state the fridgemate has a minimum of 2 degree swing from when it kicks in to when it cuts off. As my probe is on the side of the fermenter measuring the beer only it means my beer swings 2 degrees during fermentation. Which to me is not ideal.

One solution I have is to use a PID controller. I know you cant use this as a true PID controller with the solid state relay (SSR) but you can set them for on off control and adjust the differential.
So far I have set mine at 18 degrees and the differential is only a few point of a degree each way giving me a much tighter temperature control. The differential is the factory setting so will play around with it to see what parameters I can adjust to.

As the temperature of the beer will not fluctuate up and down very quickly, this should not damage my fridge by coming on and off at a fast rate, unless the differential swing is only 0.1 of a degree each side of the set temperature.


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## stm (30/9/13)

So, it seems to me (based on the analysis by niggle and thirsty) that if you don't have access to very sensitive control equipment like kenobi does (eg, you just have a standard fridgemate), then the best approach for a stable wort temperature (at the desired actual temp) is to just hang the probe in the air at about two degrees below where you want the wort to be. The fridge will cycle more often, though. If you control against wort temp, you are going to get at least a two degree variation and probably more, given that there will be overshoot, both on the way up and on the way down. Niggle's graphs demonstrated that very well.

This is what I do (probe in the air, measuring fridge air temp) and it seems to work well for me. My fridge (very old) does not cycle frequently at all, and it seems to handle it fine (particular at ale temps such as 16 degrees). If you are concerned about frequent cycling, then maybe a compromise of measuring a cup of water would do (but it is a compromise).

YMMV!


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## Rocker1986 (1/10/13)

I use an STC-1000 on my brewing fridge. I tape the probe to the side of the FV underneath a double layer of foam and set it to whatever temperature I'm fermenting at with a differential of 0.3C. Fridge comes on when it gets 0.3C above set temp and turns off when it reaches set temp. It never overshoots either up or down, so my wort is only moving that 0.3C (or thereabouts) per cycle. Certainly no 1-3 degree swings. I have measured the temp of the wort itself when taking samples at various stages and it's always pretty much spot on to what the STC is telling me it is, so I'm happy with that and my beers always turn out well. Or well enough for me to be satisfied with them.


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## O-beer-wan-kenobi (1/10/13)

Rocker, I just checked out the STC-1000 and that has settings of 0.3 degrees each way. I think these units would be fine as its only a 0.6 degree fluctuation overall. The trouble is a fridgemate has 1 degree setting each way, so to have the probe on the side of the FV and insulated is going to potentially have the beer fluctuate by at least 2 degrees while fermenting.

I think the best way for temp control is to measure the beer temperature, that way you know exactly what the temperature is and you are reacting immediately to any temp change. If I was going to buy a temp controller I would be looking at the difference set value range and get one that has the smallest range or go for the STC-1000 that has a range of 0.3 - 10 degrees.


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## Rocker1986 (2/10/13)

I'm not familiar with the fridgemate, but from my experience with the STC on my brews, they don't overshoot in either direction, using the method of taping the probe to the FV. It switches the fridge off once it hits the set temperature, rather than letting it go 0.3C under that first. Occasionally it might drop 0.1 of a degree, but usually the fermentation activity seems to be enough to prevent this. Once it goes up 0.3C, it kicks the fridge back on to bring it down again. And so on and so forth. It sounds to me like the fridgemate lets it go the differential value under the set temp before kicking in heating or whatever to bring it back up, is that right?

I have noticed the temperature overshoot downwards when measuring the ambient air temperature in the fridge, even though the STC turns it off when it reaches set temp, but given that I get accurate readings from taping the probe to the FV, that's the method I use.


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## Thefatdoghead (2/10/13)

Rocker1986 said:


> I'm not familiar with the fridgemate, but from my experience with the STC on my brews, they don't overshoot in either direction, using the method of taping the probe to the FV. It switches the fridge off once it hits the set temperature, rather than letting it go 0.3C under that first. Occasionally it might drop 0.1 of a degree, but usually the fermentation activity seems to be enough to prevent this. Once it goes up 0.3C, it kicks the fridge back on to bring it down again. And so on and so forth. It sounds to me like the fridgemate lets it go the differential value under the set temp before kicking in heating or whatever to bring it back up, is that right?
> 
> I have noticed the temperature overshoot downwards when measuring the ambient air temperature in the fridge, even though the STC turns it off when it reaches set temp, but given that I get accurate readings from taping the probe to the FV, that's the method I use.


How long have you had your STC set-up with 0.3 degree differential? 
Just wondering because my fridgey mate told me the compressor wouldn't last long if the controller was set to less than 2 degrees.


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## Rocker1986 (2/10/13)

I thought it was more dependent on how often the fridge comes on than the differential setting, although I guess that would affect it. It does have a compressor delay in it too in case the temp rises too quickly. Anyway I've had it set like that since about the start of the year, or whenever it was that I got it, haven't had any problems so far. The fridge is about 60 years old too.


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## O-beer-wan-kenobi (2/10/13)

Gav80 said:


> How long have you had your STC set-up with 0.3 degree differential?
> Just wondering because my fridgey mate told me the compressor wouldn't last long if the controller was set to less than 2 degrees.


If you are measuring the temperature of the beer from the side of the FV and the probe is insulated you should be OK. It will take some time for 20l of beer to move from 0.3 degree below the set temp to 0.3 degree above.

If the probe was hanging in the air the fridge is likely to be switching on and off much more frequently.

Like Rocker said you should be able to adjust the compressor delay time so that there is a delay before the fridge comes on and you are not constantly turning the compressor on and off.


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## Rocker1986 (2/10/13)

Yeah, it usually takes my brews at least 10 minutes, if not 15-20 minutes to rise 0.3C from the set temp which kicks it back in. Mine never go below the set temp anyway. The only brew that did drop was the current batch. It dropped to about 17.5 (set at 18), during the lag phase, but once the yeast got going it didn't go below 18, just fluctuated between 18 and 18.3, which confirms for my situation at least that the yeast activity prevents overshoot downwards. Having said that, I've noticed after fermentation has finished, it doesn't overshoot downwards either, so maybe it was just because the fridge was on a bit longer at the beginning to bring it down to 18 from 22 or 23 or whatever it was at when I pitched it.


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## [email protected] (2/10/13)

G'day All,

I have one of the 16 amp Keg King temp controllers (fridge and heat pad) which has a hysteresis of .1, although I have it set to .2. I have the probe into the fermenter via a plastic bulkhead, also from Keg King. It seems to hold he temp within the .4 range fairly well with little or no over/ under shoot. Although I must admit that I have not calibrated my controller I will need to address that. 

Thirsty Boy's idea is interesting I had not thought of controlling the temp that way before.

Regards,

Andrew.


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## jacknohe (2/10/13)

Not sure if this will add much value but I use a 1.25L glass bottle with water in it and place my probe in that. The glass bottle sits right next to my 20L jerry can fermenter in the fridge, which is a small bar fridge. I've found that this stops any wild swings from opening the door, etc. I've found that once the initial temp is aligned, the probe will be about 1c less than the stick on thermometer on the side of the fermenter. I just set the controller to 1c less than what I'm aiming for and my ferments are orsum!

This has been working great for a couple of years now.


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## Parks (2/10/13)

It's worth noting that even though your fridgemate will cycle +-1 degree (eg, from 17-19 for 18 degree setpoint) it's really only a 1 degree swing when you realise that 17.4 is rounded down and 18.5 is rounded up.

I had a thermometer in my fridge which read 10 degrees on a brew fermenting at 18 (probe stuck to the side covered with a stubbie cooler).

I know this was 4 years ago but Screwy - there's no way your wort could be colder than your fridge temp with the heat fermentation creates.


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## Bax (2/10/13)

Rocker1986 said:


> I thought it was more dependent on how often the fridge comes on than the differential setting, although I guess that would affect it. It does have a compressor delay in it too in case the temp rises too quickly. Anyway I've had it set like that since about the start of the year, or whenever it was that I got it, haven't had any problems so far. The fridge is about 60 years old too.


I'm in the exact same boat, the fridge is an old Kelvinator that was left behind when I bought the house, it was the old owners beer fridge. It seemed fair that I should convert it into the fermenting fridge.

I also use an STC1000, I believe my swing is at .5 but I feel as though that could drop to .3 easily. We've had some really hot days here the past few weeks, 35 kind of average temp. And truth be told, 9 times out of 10 when I'm downstairs in the vicinity of the brew fridge, it's off. 

With all those people measuring a jug of water or something, how is that allowing for the temp rise of the wort. Doesn't the temperature of that increase slightly as the yeast does its thing?


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## Parks (2/10/13)

Bax said:


> With all those people measuring a jug of water or something, how is that allowing for the temp rise of the wort. Doesn't the temperature of that increase slightly as the yeast does its thing?


The jug / bottle of water method should only be used in the keggerator IMO.


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## Rocker1986 (2/10/13)

Yeah, I personally don't subscribe much to the idea of sticking the probe in a jug of water. For starters it's a much smaller volume of liquid, so it will change temperature faster, secondly, it's not fermenting and thereby not creating any heat, as the yeast will do in the actual wort. It's basically comparing apples and oranges from my viewpoint.

I actually measured my beer temp sample with a Hanna thermistor thermometer today when I took a reading and it read about 1 degree lower than the STC was reading.. so I'm gonna chuck a 5 litre flask of water in there once it's bottled with the STC probe in it set to whatever, and see if it reads different on the thermometer.. might need a calibration. :unsure:


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## Thefatdoghead (2/10/13)

Rocker1986 said:


> Yeah, I personally don't subscribe much to the idea of sticking the probe in a jug of water. For starters it's a much smaller volume of liquid, so it will change temperature faster, secondly, it's not fermenting and thereby not creating any heat, as the yeast will do in the actual wort. It's basically comparing apples and oranges from my viewpoint.
> 
> I actually measured my beer temp sample with a Hanna thermistor thermometer today when I took a reading and it read about 1 degree lower than the STC was reading.. so I'm gonna chuck a 5 litre flask of water in there once it's bottled with the STC probe in it set to whatever, and see if it reads different on the thermometer.. might need a calibration. :unsure:


Bit off topic but I think its worth mentioning that the centre of the fermentor is going to be a few (from memory)degrees warmer than the wort closest to the fermentor wall. 
I haven't tried measuring the centre of my 60L ferm but there was a good article in one of the BYO mags that pretty much proved the heat difference from centre to wall. 
Some sort of wireless floating temp probe would be good to try. Or one that records for a week and then shows a graph of what temps did what and when.


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## Rocker1986 (2/10/13)

That's a good point actually. Although when I measured the temp with a different thermometer on previous readings it's come out basically exactly what the STC was reading, so one of them is out by a bit. The Hanna measured 100.7C in boiling water, although I know that can be affected by surrounding environment.

At the end of the day it can't be too bad.. the beers taste bloody good. :lol:


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