Freezer temp controll

I just got a chest freezer for $40, in great shape.

Does anyone know what is the best way to control the temperature of the freezer?
How much should I expcet to pay for the controller?

Thanks

 

I use a Johnson A419 with both of my chest freezers (one is a ferm chamber, the other is a kegerator). They work great. Very simple and easy to use. Ready to go right out of the box, just set it and forget it.

There are certainly cheaper options out there, especially the DIY options, but I have no experience with those and cannot comment on them.

 

The $20 STC-1000 that many brewers use is a dual temperature controller. You wire it into a standard 2-plug outlet that you mount in some kind of project box (either homemade or bought at Radio Shack). One (cool) outlet is for the freezer/fridge. If your fermenter chamber is placed where it’s cold (like a garage in winter), you plug some kind of small heater into the warm outlet and then put that heater inside the freezer. Otherwise, just use the cold outlet.

Set the target temp (in Celsius) on the STC-1000. Set the tolerance (default is +/-0.5*C). When the temp (as read by the sensor) climbs 0.5*C above the target, it powers up the cool outlet and keeps it energized until the temp drops to the target and then turns it off. Likewise with the warm outlet if it gets 0.5*C too cool. You tape the sensor on the side of the fermenter and place some kind of insulation like bubble wrap over top of it so that it reads the bucket temp and not the air.


http://www.amazon.com/Elitech-All-Purpose-Temperature-Controller-Thermostat/dp/B008KVCPH2/ref=sr_1_1?ie=UTF8&qid=1399600729&sr=8-1&keywords=stc-1000

http://www.homebrewtalk.com/f170/stc-1000-setup-beginners-433985/#post5538096

http://www.homebrewtalk.com/f51/ebay-fish-tank-controller-build-using-wal-mart-parts-261506/


http://www.homebrewtalk.com/f51/ebay-aquarium-temp-controller-build-163849/



http://brewstands.com/fermentation-heater.html

 

Yep, go with the STC-1000. You can get it on Amazon now for about 17 or 18 bucks for the controller. It's really easy to wire if you have any experience at all and works great! I just hooked mine up to my "new" $50 freezer that I'm using as a ferm chamber and am loving it! Took a bit to get it equalized, but now it's running great.

I will add this: get a computer fan (either just buy one off Amazon or get one out of an old computer) and put it in there running constantly. It gets all that cold air off the sides of the freezer and into your fermenter. Without it mine was taking forever to actually cool my carboy. Once I fired up the fan it got the temp where I wanted it very quickly.

 

I like both ideas. I personally went with the Johnson controls A419 from Amazon without the cord... which made it drastically cheaper. Extremely happy with it. One thing though... i read everywhere that you should tape the sensor to the bucket. I understand the theory, but have seen no difference in testing in my unit... I personally just have the sensor taped and hanging about 3" from the top. Although mine can't heat/cool at the same time (you flip a jumper)... i didn't want both items to run at any time anyway. Its either cold OR hot here in Pennsylvania...

 

The reason for wanting dual control for fermenting is when cooling, the fridge may turn off when it reaches your desired temp but it may continue to cool down a few more degrees. It will then stay there for a little while until it slowly heats up passed your set turn on temp which it will then cool again and so on. Having dual control, the heating unit will heat the air up faster so the fridge stays within a degree of the temp you need and won't have temp swings.

The reason for taping to the bucket is to get the most accurate temp reading you can. Having it just hanging in your fridge is only taking the ambient air temp which will always be lower than your beer temp. In a small fridge the difference won't be as much as if you had it fermenting in you closet but it is still a difference and can cause off flavors if fermentation really takes off.

 

I did a data log of the air temp in a freezer vs the temp of a five gal bucket of water.

While the air temp exhibited a clear and definite sawtooth pattern as the cooling cycled, the liquid temp as measured by direct immersion probe exhibited only a smooth line in temperature change. This is because the thermal mass of the bucket of liquid does not respond to changes in temp as short as the individual cooling cycle swings of the air temp. Only the (relatively speaking) long term average temp of the air influences the cooling of the liquid, not the individual cooling cycle swings of a couple/few degrees either way.

If controlling by air temp it is not necessary to have heating and cooling fighting each other to try to maintain a miniscule variation in air temp. The only reason heating is necessary is if the average temp in the ferm chamber is lower than your desired ferm temp.

 

Edit: never mind, misunderstood post

 

Yes I agree with what you found. The 5 gallons of water will stay pretty constant as it takes water longer to heat up than air. However, your experiment is missing one large variable...your 5 gallons of water doesn't heat up like beer does when fermenting. I don't know what the outcome would be but you need to try the experiment again with a good fermentation. Fermentation can put out a good amount of heat. I have seen up around 10* higher. My thinking is during peak fermentation, the beer could be hotter than the ambient air so the probe that is hanging in air will not be taking an accurate reading.

Also, you said the air temp swings were pronounced and sawtooth where as the water temp swings were smooth. What was the high and low temp readings of the water? That will make a difference too. The temp changes can be as smooth as glass but if the swing goes from 61 to 93 (obviously exaggerated) it is not good for the beer.

I wish I had the tools to do this experiment. It would be cool to see what kind of temp swings we would see (if any).

 

You need not make it more complicated than it really is. If you follow a couple of simple steps, it should go quite smoothly.

1) Pitch into wort that's a few degrees cooler than your target ferment temp (usually targeting the low end of optimal for the yeast being used). Set the controller for your target temp.

2) Tape the sensor to the side of the bucket/carboy and insulate over it with bubblewrap or something similar. The reading there is really close to what you would get using a thermowell in the middle of the liquid.

 

In my experience using a STC-1000, taped to the side of the fermenter and covered with foam provided the best results. I tried the sensor in a bucket of water, and the temp swings in my wort were way too much, as well as cycling the heat. cool, heat, cool, heat, you get the idea. I agree with pitching the yeast in a fermenter with the wort cooler than my setting is. Do yourself a favor, pitch yeast, set thermostat, and walk away. Since the wort is going to heat up as fermentation starts, turn heat off, unless your garage is colder than your fermentation temp. If you only turn on 1 action of the controller, ie, cooling only, there will be no heat, cool, on and off. Yes the fermenter will call for heat, but remember the wort will settle down if you let it.
Does this make sense?

 

There weren't any swings, per se, in the water temp. It was a smooth decline to the setpoint from starting of roughly 70F to 50F setpoint of the thermostat, with +/- 2.5F. Not saying this is the most efficient way to use the freezer, but more the point there isn't such a need to have such tightly controlled temp swings due to the mass of the liquid resisting the change.


http://www.homebrewtalk.com/f11/using-fermentation-chamber-378397/#post4749018

 

I am using an Arduino Uno with DS18B20 temperature sensors. Still working out the system but so far I am able to hold temps fairly consistent.