New Take On Freezer Conversion

So my awesome Fiancé found me this sweet freezer on Craigslist for free. It was in a basement flood and one of the connectors shorted out. I took it apart fixed the short and plugged it in and it kicked on. It got cold immediately and sounded fine.





Right now it’s just hanging out with some buckets in it (Scottish Ale and Russian Imperial Stout) that are done fermenting and are now conditioning. I put some frozen jugs of water in there to get it chilly in there. As you can see it has been holding steady at an ambient 49F for about 18 hours now and the buckets are reading about 53F on the thermo strip. Theoretically it can hold 4 fermenters (got to strengthen that shelf).

Now, for my idea. I have a programmable Honeywell Thermostat. It doesn’t matter that it’s programmable because I can set it on a permanent temperature and keep it held there. I'm thinking of adopting an idea from the Son of a Fermenter Chiller and Mother of a Fermenter Chiller concepts. I'm thinking of using the Thermostat to control a relay to control the power of the freezer. It would have to be a 12VDC Coil capable of supporting 120VAC on the switch side. The freezer is only 5 amps so I won’t have a problem with supporting that.

The Thermostat has a swing of +/- 1F and the freezer seems capable of holding temperature very well so my question is:

Has anyone tried this, or heard of this idea?

And, does anyone have any comments/concerns/ideas?

As soon as I get out and find a relay I will report back.

Edit:

How does this look?

http://www.123securityproducts.com/rdc12.html?CS_003=691061&CS_010=rdc12



* 12VDC operation.
* Coil draws 80mA.
* 10 amp/120VAC/28VDC or 10 amp/277VAC DPDT contacts.
* DIN Rail mountable.
* Dimensions (approximate): 1.375”W x 2.7”L x 2.375”H

I know it's a Double Pole, but I don't have to use both poles. its $14.00 plus shipping.

 

Not sure what a relay costs, but this isn't really any different than buying a Ranco controller for $50 or so and using it.

If you can get a relay cheap, then it should work just as well.

 

Was actually just talking to someone today about this. Apparently they make thermometers that do this... off the shelf.

 

Yes (10 char)

 

If you can't adjust the temperature swing by more than 1 degree, you might be cycling the freezer a bit much. Most temp controllers have increments of up to 10 degrees allowing more change in ambient temperature before the power kicks back in.

 

I just committed to buying a Johnson Controls Unit on ebay for 24.99+7.95.

I'm still going to try out my idea on another unit.

 

see these links:
ENGINERDIA: Fermentation Temperature Controller
Digital Controller
temp controller - Realbeer.com Beer Community

It's been done, and you can do it!

 

subscribed

 

To follow up on this, the problem is that air temp swings wildly, and the probe will pick up on that.

To solve that issue, you want to build in a thermal buffer, something with a lot more thermal mass than your probe so that the wild swings aren't constantly cycling your fridge.

Easiest way to do this is to immerse the probe in some liquid. Fill a pop bottle with water, punch a hole in the cap, and stick your probe through the cap and into the water. Voila...now your probe will take a lot longer to respond, (as the water will take a while to heat up and cool down), and your fridge wont' cycle as much, BUT will still hold the same temperature on average....and you are worried about the temp of your beer anyway, right?

If your probe isn't waterproof, a quick dip in some hotglue/wax, or plasti-dip, should do nicely.

 

Your idea with the relay and home thermostat will work just fine. Just remember that you need to supply low voltage to the thermostat relay so that it can turn on the external relay.
All in all though you made a good decision, there are so many temp controllers out there that are cheaper than the cheapest digital thermostat...

 

I stumbled into the Johnson controls so I will be using that but I am still curious as to how well it work. I'm going to attempt it at some point and document my results and everything here for everyone. I was concerned about the cycling issue but with a thermal buffer I think it will work just fine.

 

I tried this method years ago and abandoned the idea soon after. IMO it's better to have the controller probe in the air and a separate thermometer immersed in the water bottle. I use a cheap indoor/outdoor digital thermometer with it's probe in the water bottle. The probes are well sealed and designed to be weatherproof. I don't bother with a thermowell. Basically I set the controller fairly low (varies, but 62 F isn't unusual) initially while monitoring the temp. Then I monitor both the airlock activity and the temp and adjust accordingly. The water bottle approximates the wort in the fermenter and I adjust downward 4-6 deg to compensate for heat generated during the ferment. I usually let the temps rise to 68 F when it's pretty much finished out. This gives the yeast a little assist to clean up any remaining sugars they can savenge.

 

http://www.homebrewtalk.com/f51/diy-temp-controller-build-133364/

It also has a link to reelbeer.com that someone else posted int his thread.