Author Topic: Fermentation Fridge - Thermocouple Placement?  (Read 16874 times)

Offline durrettd

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #15 on: November 16, 2012, 11:37:16 AM »
If your temp controller's sensor is taped to the fermenter, and if there is a 2-to-3 degree difference in your cooling (or heating) on and off temperatures, your beer will be constantly varying between the cut-on and cut-off temperatures. If your temp controller is sensing the air temperature, your beer will be fluctuating a fraction of the difference between the cut-on and cut-off temperatures.

I've read that some yeasts are highly offended by temperature variations. That raises several questions: Do I believe everything I read? (Not for several decades.) How much variation does it take to affect yeast activity? How much does the temperature of the beer vary if the ambient air is varying 2-to-3 degrees? What am I missing here?

Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #16 on: November 16, 2012, 12:22:27 PM »
If your temp controller's sensor is taped to the fermenter, and if there is a 2-to-3 degree difference in your cooling (or heating) on and off temperatures, your beer will be constantly varying between the cut-on and cut-off temperatures.

You are correct.  You solve that particular problem by using controllers with tighter tolerances than 2-3 degrees.  An STC-1000 have a minimum differential of 0.3 C or 0.54 F.  If you heat AND cool...then the total swing is 1.1F. 

Second, if you keep the beer in a cold room (10F or so below desired beer temperature), then you only have to HEAT the beer to hold the temperature...and let it cool naturally.  This approach drops the total swing back to ~1/2 F. 

Quote
If your temp controller is sensing the air temperature, your beer will be fluctuating a fraction of the difference between the cut-on and cut-off temperatures.

In the short term, this is true...assuming that the beer is not producing any heat of its own.  My experience says that its about 1/3rd of the air temp swing.  That said...it is HIGHLY dependent on local factors: size of the batch, fermenter material, size of the fridge, mass of the fridge, etc.   

The other issue to consider is the "assumption" in bold above.  Its not a valid assumption.  An active fermentation produces a LOT of heat.  A completed fermentation produces NONE.  The beginning and the end produce somewhere in between.  The amount of heat depends on how active the fermentation is.  the more vigorous the fermentation, the more heat.  Hefe yeast is notoriously active.  I have seen hefe fermentation raise the temperature of the beer 12 F above the air temperature at the peak of fermentation.  A more typical number is around 5 F, though.

If you hold a constant AIR temperature, then the extra heat of fermentation will simply raise the temperature of the beer by the amounts described above.  So, you are holding your fridge at 60F, and the hefe raises another 12F for a BEER temperature of 72F.  In fact if a Hefe yeast were allowed to get up above 68F or so, it might take off like a rocket and produce even more heat...maybe landing above 75F.  Now you have a bubble-gum flavored beer.

Or....you anticipate this temperature rise...and set your fridge to 50F.  50F is too cold for the Hefe yeast to get started and ferment vigorously...so it ferments very slowly (if at all).  Thus it produces only a couple degrees of temperature rise.  Your hefe ends up fermenting at 53F (or so).  Now you have zero Hefe flavors...and the fermentation may not complete.

These effects are most pronounced with Ales. 

Quote
I've read that some yeasts are highly offended by temperature variations. That raises several questions: Do I believe everything I read? (Not for several decades.) How much variation does it take to affect yeast activity? How much does the temperature of the beer vary if the ambient air is varying 2-to-3 degrees? What am I missing here?

Some yeasts are ABSOLUTELY affected by temperatures, and temperature variations.  Some not so much. 

Kolsch yeast is notorious for dropping out of suspension if subjected to frequent, rapid, large, temp swings. 

I cannot get Cal Ale to ferment below 65F...even that I have a hard time with. 

hefe yeast I've described above.

Saison yeasts are notorious for quitting early without a significant rise in temperature over the ferment.  But, you can't START high, or they will produce nasty high-order alcohols. 

Most belgian strains produce very different flavors over a very small temperature range. 

http://www.whitelabs.com/beer/BelgianYeastStrains.pdf

I'm playing around with WLP570 right now.  And I promise the chart above is very accurate for that strain.

So, if you want to target a specific flavor from a belgian yeast, you have to control the BEER temperature withing a degree or two during the first 72 hours of fermentation---after that it doesn't matter as much.  But, this is during the lag and ramp phases of fermentation where the heat produced by the yeast is increasing.  Without good sensing of the beer temperature, you'd never be able to hold the needed temp range.

You don't have to believe what I'm writing....go do the experiments yourself.  You will quickly find that sources like Jamil Z, White Labs, and Wyeast are very reliable...and won't need to continue to prove everything they say to yourself.  I don't quote information from any source other than the ones I just listed.  I've done a few tests of my own, and I've never managed to do anything except confirm the results reported by these authorities. 

At this point, I take those sources information at face value.  Any experiments I might try, in this regard, are limited to assessing a specific desired recipe characteristic rather than trying to completely characterize a yeast.  If I want spicy, I target the spicy temp range.  If its too much/not enough, I adjust a degree or two on the next iteration.


R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline Wingeezer

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #17 on: November 17, 2012, 09:05:09 AM »
I use those flat elastic bungie cords that you can now buy with the plastic hooks on the end.

The elastic is maybe an inch or more wide.  The ones I have are adjustable so I can easily use them on different size carboys or on kegs.  I just wrap the bungie around the container,  clip the hooks together and put the probe under a small pad of foam insulation and secure it under the bungie tight  against the container.

Never really tried tape, this just seemed and easy way to do it.

Brian
 

Offline durrettd

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #18 on: November 17, 2012, 01:24:05 PM »
Tom,

Nobody told me when I stared brewing that I was going to have to THINK!

Thanks for doing the hard work to research and quantify so many of the moving parts of brewing. Thanks also for the endorsement of Z and the yeast labs.

Dan

Offline ihikeut

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #19 on: November 17, 2012, 08:12:32 PM »
I have to second that. I learn as much from Tom's post as I learn from many books I have read on brewing beer.

Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #20 on: November 17, 2012, 08:59:02 PM »
::blush::

Thanks.   Full disclosure, I'm an aerospace engineer. So, a lot of this mathy stuff is old hat. :-)

I only have 5 books on brewing:

How to brew, John palmer
Brewing classic styles, John Palmer & jamil z
Yeast, Chris white & jamil z
Designing great beers, ray daniels
Brew like a monk, Stan hieronomous

Other than that I listen to the brewing network every day.

I try to pass on what I can.


R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline grathan

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #21 on: November 18, 2012, 05:14:20 PM »



Good stuff tom. Any idea if the hot side of the stc-1000 10amps could handle a 1500 watt heating element?



Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #22 on: November 18, 2012, 08:08:16 PM »
Nope.

1500 watts / 120 volts = 12.2 amps.

For longevity, never run a relay past 75 percent of its rating. 

R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline grathan

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #23 on: November 25, 2012, 10:52:44 AM »
You've got the right idea, Phil.  If you want to control the beer temp, you need to measure the beer temp.  The activity of fermentation generates quite a bit of heat.  So, your controller will have to work hard before fermentation starts, and after fermentation finishes....but, in the middle the yeast will do a lot of the work themselves.

In the future, you will want to get more controllers.  One for the air temp inside your fridge, and one for each beer.  I use heating pads to heat each carboy or bucket while keeping the air temp down at 45F or so.  I can ferment several different beers at several different temperatures this way...

I've been thinking about this lately.... Can you do a lager 45.0F next to an ale 68.0F using this method? You don't happen to have a link to the type of heating pad that you use?

Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #24 on: November 25, 2012, 09:45:28 PM »
http://www.amazon.com/gp/aw/d/B000F54AOW

But, if I do more I will use heat tape.

My fermentation room is sitting at 8C.  I have routinely ferment ales at 21C. I use buckets with the above heating pads, and an stc1000 temp controller. Then I cover the fermenter with reflectix insulation. 

Attached is a pic of half of my setup.
R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline piper55

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #25 on: November 28, 2012, 08:22:17 PM »
I use a brew hauler on the carboy and stick the probe in between the hauler and the carboy