Fermenter In Fridge

[QldKev]

I have a fridge set up with tempmate controlling the fridge on one side and a heater belt on the tuther.

Set and forget B)

I, like Boagsy live in "the undemocratic queens republic of Tasmania" (Long story but it has something to do with politics) and brew with this setup all year, hot cold, dosent matter

i insulate my probe to the outside of the ferm..someone once told me that there was up to a 4 deg difference between the centre of the wort and the outside of ferm

I take it whoever told you that has never watched fermentation through a glass vessel. With the amount of activity turning over the wort; I cannot see that possible. But I have never actually measured it.

QldKev

 

[QldKev]

Off to take some measurements of real live values.

QldKev

 

[QldKev]

Back from measurements.

I run 2 fermentors in my fridge; one on an upper shelf and the other on the lower shelf.

Dixel controller set to 18.0

Top fermentor
Edge touching fermentor 18.1 (**** a lot closer than I expected; must have jagged the time between fridge cycles)
Measurements at center, approx just above half height (as deep as my thermometer measures). 18.1 same

Bottom fermentor
Edge toughing side 19.2 ( I thought coldness drops, so thought this would have been colder)
Center 19.2.

Overall
I did expect 0.2 difference between centre and egde, but did not show it at 2 days into fermenting. Maybe later stages once the activity settles down.
I also expected the bottom fermentor to be colder, but now assume that since the top fermentor is close to the cooling area of the fridge it has the best heat exchange. It may be worth setting up a pc fan to circulate air.

QldKev

 

[Oatlands Brewer]

Thanks Kev, i was a little bit dubious of this anyway but it was explained that fermentation was a exothermic reaction thus creating its own heat. i guess following this logic that it would be its hottest at its most active, but you have just proved that incorrect....so i dunno.

 

[QldKev]

Thanks Kev, i was a little bit dubious of this anyway but it was explained that fermentation was a exothermic reaction thus creating its own heat. i guess following this logic that it would be its hottest at its most active, but you have just proved that incorrect....so i dunno.

I think the statements are correct. Beer fermenting is an exothermic reaction, but to what level? While beer is fermenting vigorously at its peak, producing possibly its maximum exothermic load, it is also causing the most activity forcing it to also turn over the most volume of wort recirculation; circulating the wort between the center core and the external layers; hence a uniform temperature dispersion.

Now I am speculating based on what I have seen in activity and what I have just measured. But it does seem logical.

QldKev

 

[Bribie G]

Straying a bit here, but does anyone reading this have a Fridgemate installed and notice that:

Set to 18 it will slowly rise (according to the probe which is just hanging down the side of the fermenter and not stuck on yet) to 20. Then the fridge kicks in and drags it down fairly quickly to 17. Then fridge cuts out and it rises to 20 again.

A check with my laser "pointing" thermometer indicates that the fermenter surface is at 17.8 so obviously the system is doing 18 but the 'cycling' of the temperature numbers on the LED display is a bit slacko.

 

[itmechanic]

Bribie,

As the temp probe is not stuck to the side of the fermenter, it is measuring the air temp inside the fridge which heats and cools a lot quicker than the large thermal mass of a fermenter full of wort. Try sticking it to the side and insulating it from the outside air with a bit of foam or old carpet or something and you will see a big difference and the fridge wont cycle as often.

Cheers,
Paul

 

[GTS350]

My tempmate probe sits at the bottom of a stainless diptube "in-the-wort". The wort temperature is +/- 0.5deg and its one more step toward perfect beer. :beerbang:

The sealed diptube (aka thermowell) hangs down into the wort from the fermenter lid. I sealed the diptube up by welding half a stainless washer onto the bottom, then filing it smooth.

Ive also had great results using a 4inch computer fan to circulate the cold air inside the fridge. That way both fermenters stay at the same temp. highly recommended.

Cheers,
Richie

 

[Bribie G]

Thanks for that guys, will tweak the system, and I'm sure the poor old fridge will breathe a sigh of relief and won't be going "WTF" every ten minutes

 

[bum]

As the temp probe is not stuck to the side of the fermenter, it is measuring the air temp inside the fridge which heats and cools a lot quicker than the large thermal mass of a fermenter full of wort.

Which is why I leave my probe just hanging in the fridge so the temp of the wort doesn't swing for each cycle. Yeah, this method cycles the fridge more often but still not as much as a fridge used for normal domestic purposes so I should still get a fair run out of it.

 

[Barley Belly]

I used to hang mine Tempmate probe just in the air but the temp fluccuated too much
So I changed to strapping to the fermenter under some styrofoam, similar probs

Then I came up with strapping it to a Coopers PET bottle filled with water and insulated with camping mat, works well

 

[Pennywise]

I get very stable temps just sticking the probe to the side of the fermenter with a big piece of blu-tac over it, I figure the blu-tac keeps a pretty stable temp too sothe actual ferment temp is being measured.

 

[theredone]

My tempmate probe sits at the bottom of a stainless diptube "in-the-wort". The wort temperature is +/- 0.5deg and its one more step toward perfect beer. :beerbang:

The sealed diptube (aka thermowell) hangs down into the wort from the fermenter lid. I sealed the diptube up by welding half a stainless washer onto the bottom, then filing it smooth.

Ive also had great results using a 4inch computer fan to circulate the cold air inside the fridge. That way both fermenters stay at the same temp. highly recommended.

Cheers,
Richie

how do you go about wiring in computer fans? they run on an 18v system dont they?

sounds like a great idea and i heave access to a heap of these things

 

[QldKev]

how do you go about wiring in computer fans? they run on an 18v system dont they?

sounds like a great idea and i heave access to a heap of these things

computer fans run on 12v, easiest way is just use an old power supply from something like a phone. Anywhere from 6v to 12v will work; obviously the higher voltage will turn the fan faster.

QldKev

 

[Jamieman]

Maybe not relevent to this thread, but will mention it anyways.
I had issues with inadequate hygiene that only became apparent with fermentation commencing a little later in a refridgerated enviornment compared to 22-23 deg ambient.
Cleanliness becomes even more critical at lower (12 deg) temps.
Cost me 3 batches to discover this. (Dirty Tap)

 

[RobboMC]

I take it whoever told you that has never watched fermentation through a glass vessel. With the amount of activity turning over the wort; I cannot see that possible. But I have never actually measured it.

QldKev

Theoretically the temperature difference reflects the SPEED of the heat movement.

So if you are using your fridge to get a warm wort down to a cooler temp then by definition
the wort must be warmer in the middle than the outside. If the outside temp is constant day after day
than again the internal temp MUST be the same as the outside, otherwise the outside temp would change
to balance it. Think of a playground see-saw, you only have to measure where one end of the see-saw is,
and measure the slope, to know where the other end is. The heat must always be flowing from hot to cold,
just like water running down a slope. A temp strip on the inside wall of your fridge will help immensely.
If fridge inside wall temp equals fermenter outside temp then you very probably have no temp variation inside fermenter.

I used this concept effectively in the metal industry to 'measure' the internal temp of big metal blocks,
by measuring the outside over time and measuring heat flow through the surface. Sound complex but is
quite easy in practice.

Big temp variations can occur on brew day. I once was pouring kgs of ice into a warm brew and it wasn't cooling
much on the temp strip, so popped in a thermometer and found 5 deg difference, had a cold centre and warm around
the outside due to lack of stirring and impatience.

But after a few hours the temp differences will resolve themselves through natural convection and conduction even without
any fermentation turbulence. Hot and cold will find and balance each other just as relentlessly as yeast will consume sugar.

 

[QldKev]

Theoretically the temperature difference reflects the SPEED of the heat movement.

Yep, temp diff and the substance


So if you are using your fridge to get a warm wort down to a cooler temp then by definition
the wort must be warmer in the middle than the outside. If the outside temp is constant day after day
than again the internal temp MUST be the same as the outside, otherwise the outside temp would change
to balance it. Think of a playground see-saw, you only have to measure where one end of the see-saw is,
and measure the slope, to know where the other end is. The heat must always be flowing from hot to cold,
just like water running down a slope. A temp strip on the inside wall of your fridge will help immensely.
If fridge inside wall temp equals fermenter outside temp then you very probably have no temp variation inside fermenter.

I used this concept effectively in the metal industry to 'measure' the internal temp of big metal blocks,
by measuring the outside over time and measuring heat flow through the surface. Sound complex but is
quite easy in practice.

Big temp variations can occur on brew day. I once was pouring kgs of ice into a warm brew and it wasn't cooling
much on the temp strip, so popped in a thermometer and found 5 deg difference, had a cold centre and warm around
the outside due to lack of stirring and impatience.

But after a few hours the temp differences will resolve themselves through natural convection and conduction even without
any fermentation turbulence. Hot and cold will find and balance each other just as relentlessly as yeast will consume sugar.



I agree a difference in the initial period of cooling would become evident, but unless the outer edge had a huge exchange of temperature; or in your case dropping ice in, large variations shouldnt be the norm. But given extremes of heating / cooling maybe 4 degrees is possible during the initial drop of temperature. In a liquid, as opposed to the solid, convection currents causing the warmer liquid at the centre to rise, and the outer edges to fall, rotating the liquid. Hence the temp difference with become lesser quicker. Also I was thinking of high krausen, which would also cause more wort mixing; but I should have thought about the time prior to yeast activity.

It will be a good experiment next time I pitch, to measure initial temps, and at a few stages for the initial period until it stabilises. But if Im pitching at 22 and dropping the wort to 18, which would take my fridge say 3 to 4 hours, I dont think I will achieve a 4 degree variance.

 

[theredone]

I used to hang mine Tempmate probe just in the air but the temp fluccuated too much
So I changed to strapping to the fermenter under some styrofoam, similar probs

Then I came up with strapping it to a Coopers PET bottle filled with water and insulated with camping mat, works well

heatpad under each fermenter and a heat belt? looks like nice set up but is all that needed?

im going to be converting a fridge soon and i have a heatbelt and a pad. living in bris i wouldnt need both of these(if any) would i? if so was thinking of just haveing one on either side or maybe just the belt on one side with some fans blowing around

 

[QldKev]

heatpad under each fermenter and a heat belt? looks like nice set up but is all that needed?

im going to be converting a fridge soon and i have a heatbelt and a pad. living in bris i wouldnt need both of these(if any) would i? if so was thinking of just haveing one on either side or maybe just the belt on one side with some fans blowing around

I'm up in Bundy; and actually got through last winter without draging out my heat belt. It will depend where your fridge is located, mine does get hit by the morning sun for an hour to warm it up a bit (not so good in summer). Hanging the heat belt with fans to get airmovement, does sound like a good idea. I originally thought that the belt may get too hot as it won't be in contact with the fermentor; but by the looks of others it is ok.

 

[theredone]

I'm up in Bundy; and actually got through last winter without draging out my heat belt. It will depend where your fridge is located, mine does get hit by the morning sun for an hour to warm it up a bit (not so good in summer). Hanging the heat belt with fans to get airmovement, does sound like a good idea. I originally thought that the belt may get too hot as it won't be in contact with the fermentor; but by the looks of others it is ok.

yeah id have to say that even in our colder months i dont think the heat belt would even get switched on that often or for long periods of time so even if its not a pressing requirement i dont think it would hurt to have one in there anyways. especially if you have a fan blowing air from bottome to top across it.

maybe another fan on the other side blowing down to get some good circulation going on. will post in the next couple of weeks when i do mine and let u know how it goes