Is a 3.5 degree tempurature differential to much?

I just got a temperature controller for my fermentation chamber. It has a fixed 3.5 degree temperature differential. Is that too wide of a range?

In most cases...no, it's not a big deal. Keep in mind that it will take a looong time for a 5 gallon batch to change internal temp in the fermenter since the controller is reading air temp not wort temp. You will find that if set at say 64 deg, your ferment temp might go as high as 68 or so for the first few days because fermenting creates heat. But after fementation slows and stops, it will drop to 64. Use a good thermometer placed in the center of the fridge and you will be able to tune in to your desired air temp. You might have to have the controller at 62 or 66 to get a constant 64, they all read a little different, and I wouldn't count on the temp you set being accurate without checking with a thermometer.

Thanks. I have the temperature probe in a gallon of water. I read somewhere that was a good idea.

JDFlow said:

Thanks. I have the temperature probe in a gallon of water. I read somewhere that was a good idea.

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I think you would be better off taping it to the side of the fermentor.

pelipen said:

I think you would be better off taping it to the side of the fermentor.

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agreed.. grab some bubble wrap and fold it over a few times.. put the probe against the side of the fermentor and cover it with the bubble wrap.. tape it down.

oh yeah I would probably also set it toward the low end of the yeast temp range that way when it does raise the 3.5 degrees and kick on teh cooling you will be good.

It's a chest freezer with refrigeration coils running through the walls which are really thin. The walls get really cold really quick. Do you think that'd tell the controller it's already cold enough in there and shut it down prematurely? That was my worry, but I definitely respect experience over my assumptions.

thats why taping it to the fermentor works better.. it reads the temp of the BEER not the walls or the air.

OHIOSTEVE said:

thats why taping it to the fermentor works better.. it reads the temp of the BEER not the walls or the air.

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This

I just started a similar thread for a fermentation with the probe attached to the side of a carboy and the controller set for a 1F differential. The controller display shows about a 2F rise in temperature before the chest freezer is cycled. A thermocouple with data logger showed a bigger swing as indicated in the graph in the thread.

https://www.homebrewtalk.com/f163/belgian-tripel-trended-fermenter-temperature-330554/

Attaching the probe to the fermenter will create the biggest temperature change to the beer but the least amount of freezer/refrigerator cycling. My experience is that these swings do not effect the attenuation but I typically also raise the temperature by 5F towards the end of fermenation and most of the time transition to a heater controlling air temperature inside the freezer where the beer temperature stays very constant and the heater cycles more often. I'd recommend trying to find a way to end your fermenation at a stable temperature and sometimes a closet or basement is perfect.

It's also interesting to note that the shortest time between cycles indicates where the fermenation was most active.

DSmith said:

It's also interesting to note that the shortest time between cycles indicates where the fermenation was most active.

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Wouldn't that be expected considering that fermentation generates heat? It's cool to see a digital timeline. The temp swings are a lot more often than I imagined. I have fermometers taped to the sides of all my carboys including my secondary. I'm really considering just putting the probe in the open air of the fermenter and monitoring the fermometers to dial in a setting that keeps fermentation steady.

The freezer cycling didn't stop the fermenation when it was most active so it's some proof that that change wasn't too big.

Controlling the air temperature for cooling will be difficult because you will need to change your setpoint depending on how much heat the fermentation is producing. The air temperature gets very cold in a freezer to change a large volume of beer that's producing heat. At least by attaching the probe to the wall you are controlling the temperature of the fermenter in a hands-off way. I don't think controlling the air temperature works out well until the fermentation is almost complete.

I have a few more days of data now and will update my graph in a few days to show how controlling air temperature with a heater after fermentation slows creates a very consitent beer temperature.

I think you're right considering all of the experience that cosigns taping the probe to the fermenter, but my logic tells me that I know when the freezer cycles on the glass of the carboy gets cold quickly which makes me think the probe is actually going to read the temp of the cold glass and not the beer inside.

I insulate over the probe with ceramic fiber insulation in a large zip-lock bag.

When I control the air temperature by heating I tape the probe to the zip-lock bag and set it inside the freezer on top of the carboy so it's a true air temperature measurement. Here is a graph I made a few months ago for heating where the air temperature is controlled and fermemtation is finished. I was building 4W & 8W resistor heaters and both work really well with a 9V DC power supply.

I use a 5 degree temp diff on mine and the beer temp never changes because when the compressor kicks on the temp drops 5 degrees in just 3 minutes but then it takes 30 minutes for it to come back up 5 degrees. The average temp is uniform and the beer temp will not fluctuate a measurable amount.

Jayhem said:

I use a 5 degree temp diff on mine and the beer temp never changes because when the compressor kicks on the temp drops 5 degrees in just 3 minutes but then it takes 30 minutes for it to come back up 5 degrees. The average temp is uniform and the beer temp will not fluctuate a measurable amount.

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Are you using the probe for air temp or carboy temp?

JDFlow said:

Are you using the probe for air temp or carboy temp?

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Air temp. If the beer temp is fluctuating that much that wouldn't be ideal. I use a stick on thermometer on my carboy and insulate it with a rag bungeed around so that it more accurately reads beer temp. Beer temp takes a long time to be effected by small temp swings.

Controlling the air temp and watching the fermemter temp will work as long as you check on it and make the set-point adjustments.

I looked at controller specs and the Love TSS2-2100 (120V model, Degrees F) has a differential down to 0.1F. Knowing now how the A419 operates, I'd buy the TSS2 for controlling a fermenter and choose the differential that is a good trade-off between temperature fluctuations and freeazer cycling.

http://www.scientemp.com/pdf/Dual Stage Love Controller.pdf

Seems my moderate gravity beers using US-05 yeast all rise 5-8 degrees above ambient for the first 4-5 days, then start to cool down so I set my ambient to 61F for the first 5 days and then gradually raise it to 67F over the course of another 5 days and finish out the 21-28 day fermentations at 67F.

I've not had a single off-flavor in my beers since I started controlling temps this way.