Building my own dry-aging unit

[wcpreston]

Update after two days of stable operation.

Right now I have the target temp set at 37F and the trigger at 39F. What I'm noticing is a 100% correlation with warmer fridge and more humidity. Check out two days of it running to see what I'm talking about, also with another image zoomed in on one hour. You can really see the relation in the zoomed-in one.

I am thinking about letting the fridge control itself, since I have such a huge allowable range. I know if I put the fridge on "7," it's highest setting, the temp in there gets below 32F. I'm wonder where it will and if I put it at some lower number. So I'm thinking I'm going to set it at, say, 4 and turn off the upper temp limit on the controller, and seeing how warm it gets. It would be nice if I could find a setting that kept the fridge right in the middle of the range. I know it will still oscillate, but I'm wondering if it will oscillate less, as it's working as designed.

AND i'm wonder if it's oscillating less, if the humidity would not go up and down as much.

Anyway, now that things have chilled out for a few days, I'm going to play with it tomorrow and see what that does.



one.

[Red Man]

It will swing much more than that if you use the built in stat. That is a really small temp variation for a fridge. Your problem is thermal mass. I’m guessing you don’t have much in the fridge. Load that thing up with bottles of water.

[wcpreston]

I think every fridge is different. This is an old ass fridge that's performing like a champ.

I set it at 2 (its second warmest setting) and it cycled between 34.3 and 33.4. Actually pretty stinking tight. I'm going to try the 1 setting and see how it goes for the next 8 hours (sleepy time). (I'll attach the pic in a later post.)

Man I love this wireless temp/humidity sensor I got for $13.

I agree w/you on thermal mass, though. That should smooth things out.

[Red Man]

Also...It looks like your controller is set for a one degree differential between off and on. Is it possible to change that to three degrees? All that cycling is gonna wear out the fridge.

[wcpreston]

Actually, it was set at a 2 degree differential. I found that with a 3 degree differential (set to 36F as target, 3 degree diff), the swings were much wider. It would continue cooling the compartment after the freezer was shut off, and the temps would drop below 32 each cycle.

[wcpreston]

This is what the temps looked like with the fridge just set to "2," the second warmest setting.

[wcpreston]

I changed the setting on the fridge to "1" and nothing changed. I changed it around 11 PM, and you can see the the range hardly changed. Humidity seems to have gone up a smidge, but not much. Really interesting how it peaks at 85%, which is exactly where I need it to be.

Although I'm frustrated that I can't "turn on" the silica beads only when I need them (above 85%), they do seem to be helping. Before I put them in there, I was occasionally going above 85%, but now I don't seem to be.

(I also know that I have changed more than one thing at a time more than once, which is not good practice for such things.)

My next change is to add some thermal mass, as has been suggested by more than one person. Any thoughts, anyone, one whether or not it would matter if I put said thermal mass in the freezer compartment vs the fridge compartment? (This is a very old fridge where the freezer is just a metal box in the upper portion of the fridge compartment.)

The reasons I want to put it there is that it's wasted space, I don't want the water to evaporate, and I was thinking I might even save on some electricity by keeping a big block of ice in the fridge. As long as it doesn't cause the fridge to drop below freezing (which I can't imagine it doing) I think I'd get the benefits of the thermal mass AND save energy. Am I wrong?

[wcpreston]

rickgregory. But they're effectively the same chamber. Just a cold section and a colder section. . Yea.. Evaporation is probalby not a big deal. But space is. I'm already tight in there.

[wcpreston]

BTW in the sense of "change one thing at a time," I just change the fridge setting to 4, and want to watch it over the next hour to see if the temps go up or down. I'm hoping they go up. Because I'd rather the temps be just a tad higher than they've been, but I can't go lower than 1.

After I finish this, I'll add the water. I think I'm going to put it in the freezer first and see if it affects anything. Theoretically, it should cycle less often and maintain the same temp, right?

[rickgregory]

it should. While you don't want to crowd out the meat, you DO want a lack of empty space in there, though. And yeah, one thing at a time is good practice.

[wcpreston]

Here's my latest update. I'm pretty much in a state of equilibrium. It's been maintaining the temp and humidity that I want it at for a few days now.

1. I've put some "thermal mass" in the freezer. (I have a few gallon-sized bags of gel bags they ship w/the food service I use.)

2. I've set the controller to 37F w/a 1F differential. The thermometer ranges looks just like they did when the fridge was controlling things, just a few degrees higher. Now I'm going to see how they look after the gel bags freeze. (I know one of you was concerned that a 1F differential was cycling the fridge too often, but like I said above, it's behaving just like it did when it was running things, just a few degrees higher.)

3. The brisket is looking nice and aged. And it got rid of the smell that was on the surface that it picked up from the small fridge I bought. Man, that was stinky.

I've decided to fashion a silica gel-based dehumidifier by putting it in the bottom of a closed box and putting the same model fan I'm using for the big fan on one end, then turn that fan on with the humidity controller. That would blow humid air across the gel and take out the moisture. Pretty cool idea, huh? I'll take some pics and upload them when I've built it.

[wcpreston]

Here's another update. The silica gel works really well, but too well. So I had to make another change.

Here's what was happening. The silica gel would suck moisture out of the air all the time, and do so until the humidity got below what I set as the minimum, after which my controller would turn on the humidifier. Then the two of them would get in a war, with the humidifier constantly humidifying and the silica gel constantly dehumidifying. This also made the silica gel get "full" a lot quicker.

So here's what I did:

I bought another one of the 6" computer fans (with AC adapter) and a 7" high plastic storage box with lid. I cut two holes in each end, and used duct tape to tape the cut-out plastic at the top, making a kind of hanging door. Then I put the fan in one of the holes and hooked up its power supply to the dehumidifier AC port on the humidity controller. I set the goal to 80%, and told it to turn on the humidifier at 74% and turn on the dehumidifier at 86%. That way it blows moist air across the silica gel only when it has high humidity. I put a couple of pics here to show you how it looks. The box is at the bottom of the fridge below the meat.

at.

[wcpreston]

Here's what the temps and humidity look like now, for the last week. Much more stable, and I think the gel will last a lot longer now. Only problem is I don't quite know how often it is turning on either one. The humidity seems to cycle w/the power. The humidity seems to raise up as the fridge warms up, then drops as the fridge turns on. What I don't know at this point (because the temps and humidity are not exactly the same between the monitors/controllers and my wireless monitor) is how much the two are actually being turned on. I know how to find out, but it would cost me more money.

Here you can see the temp and humidity over the last week. The spikes you see are mem opening the door for longer than I should have.



Here you can see the relationship between temp and humidity.

[tbob4]

This has been a fun, interesting thread. Thanks. Keep it going.

[rickgregory]

This is interesting. But I would not worry about the humidity spikes. The range is narrow and if you average it out, dead on where you want it. Honestly, the graphs are misleading in a psychological fashion. The temp is varying by *2 degrees* and the humidity by 4%. If you zoom out and look at those on a larger scale, they're effectively flat.

[wcpreston]

tbob4 Thanks. It's been stressful on this end, but I'm learning a lot. Like I said, I just wish I had done all this experimenting before putting any meat in there.

rickgregory You got it. The temp is spot on and varies only 2 degrees. The humidity range is actually about 6%, not 4%, but it is hovering right on the magic number. At this point, I'm just trying to find an equilibrium that has me not worried the silica gel gets filled up too quickly.