Fermentation Temperature Vs Fridgemate

[Brewman_]

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

 

[browndog]

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

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

 

[Brewman_]

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

 

[Diggles]

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:

 

[Thirsty Boy]

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.

 

[O-beer-wan-kenobi]

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.

 

[stm]

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!

 

[Rocker1986]

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.

 

[O-beer-wan-kenobi]

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.

 

[Rocker1986]

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.

 

[Thefatdoghead]

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.

 

[Rocker1986]

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.

 

[O-beer-wan-kenobi]

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.

 

[Rocker1986]

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.

 

[andy@67]

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.

 

[jacknohe]

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.

 

[Parks]

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.

 

[Bax]

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?

 

[Parks]

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.

 

[Rocker1986]

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: