I bought a temp controller II from williams brewing and i cant get it figured out??

I found an old chest freezer and i plugged the controller up and put my fermenter in the freezer, taped the controller probe to the side of the fermenter with a piece of styrofoam insulating it from the ambient air. I set the controller to 68 with a diff of 3 and an asd of 1. The controller let the probe temp drop to 60 and the ambient air temp was 40? Any suggestions? I'm sure it's oversight on my part but I'm stumped. Any and all help or suggestions are appreciated. Thanks

Did you just turn it on, when you put in the fermenter? I find that I don't get the wide initial variance if I turn on the chamber an hour or so before I put the fermenter in. But yes, when I first turn it on, it turns off the chamber but keeps getting colder, going lower, until it stabilizes.

FWIW, I use a diff of 1 and an asd of 1.

Do you have it on heating or cooling mode? You want it to only turn on if the reading is above your target for cooling, so it sounds like you've got the wrong mode.

I've got it set to cooling. The interior of the freezer in the off position is above my target, it sits at like 75, so I plugged in the controller and set it to 68 and it kicked the freezer on but it didn't stop cooling once it hit the target plus diff. It continued to drop the temp to 60. Almost seems like I need a cooling setting and a heating setting going at the same time.

I will try to turn it on and put the probe in a bottle of water to test it out an see if I can get it to stabilize, maybe spend an evening just monitoring the temp with a tasty beer. Thanks for the tip.

I wouldn't put the probe in water, they aren't usually waterproof.

If you are sure it is in the right mode and it turns your appliance on when it reads below your target then it's broken. or you have it in heating mode. It should be a qui k switch and you can see if the appliance stays off when the temp is below target. Then you can put the probe in your hand to warm it up and watch it shut off the appliance.

You might give the homebrew shop a call or email to confirm settings.

Question, did the refrigerator actually switch off at the setpoint (accounting for differential)? Usually there is a little bit of latent cooling, like you will see the temp drop some amount even after the fridge turns off. If the controller switches the refrigerator off at the right temp it's working properly. Residual/latent cooling that happens afterwards you cannot address with an on/off cooler, you'd need a PID if you really wanted to tune against that.

Thanks both for the comments. I didn't get a chance to check on it today but tomorrow ill watch and see when the freezer motor shuts off. I thought about the latent cooling an thought that could be it. I will keep testing an may just have to send it back. Talked to Williams brewing and they said what's happening isn't common.

i.e. I use the STC-1000, with two 6.5g carboys in a 7cu ft chest freezer, I see 1 degree roughly of 'latent cooling'. After the freezer turns off, I get roughly 1 more degree (C) of temperature drop. So if you can observe that, you just set your setpoint that much above the minimum you want the temp to go, then adjust your differential accordingly. The largest diff you can get away with is going to be what gives the longest life to the freezer because of less on/off cycles. Usually I keep the compressor protect timer at the max, which is 10 minutes on the STC-1000 anyway, to reduce short cycling as much as possible (though if you have the diff set high enough that won't be an issue anyway).

Another 'trick' would be to fill extra space in there with water bottles, this is will slow down the response of the system.

Where the temp probe is yes can have an affect, just in the air is going to be much more sensitive than in a small container of water or taped to a carboy.

So I did a little test run this morning...the controller is set at 70, differential at 1, and asd at 1. When I got to my freezer, the controller temp was at 69 and the freezer motor was off. I pulled the probe from the water bottle, placed it in my hand for a few seconds and warmed it up to 76 degrees. Once the temperature on the controller hit my 70 degree mark, the power to the freezer turned on (good sign). Then once the temp hit 76, I placed the probe back in the freezer between the water bottle and a towel that I folded over and taped to the side. I also put a regular thermometer in the freezer to monitor ambient air temp.

I found the freezer power stayed on until i hit 69 degrees (success, controller is working fine). Once the power to the freezer turned off, the air temp of the freezer continued to drop to 53 degrees, and the probe stopped dropping at a temperature of 66 degrees. So it appears that my controller works fine, it just has a little swing when the freezer motor kicks up but isn't a huge swing.

Porcupine, I will start collecting water bottles and will fill up my freezer with those to try and decrease the dramatic change in air temperature. good tip.

One possible cause of my temperature variation may be that my freezer is in the garage. During the day, the temps are reaching high 70s-low 80s; but at night, they're dropping to high 50s-low 60s. could the outside air play such a major role? The freezer is highly insulated and I've got a 20lb weight on the lid to ensure it is completely sealed. Does anyone think I'd actually need to switch it to heating and get some heating element in the winter if left in the garage? Or should i stop asking questions and just move the thing inside?

Oh yes if the ambient temp is ever going to be less than the temp you want in the chamber, you're probably going to need a heater inside too. The refrigerator's insulation would slow heat leak from inside to the cooler outside but it is not going to stop it. I.e. especially in the winter if it's say freezing or below in the garage and you want 60F in your chamber you'd definitely need a heat source too. Not sure what your controller has, the STC-1000 has heat and cool contacts to handle that type of application, to activate the cooling if it gets too hot, and to activate the heating if it gets too cold.

Ideally for longest compressor life you want it to cycle on and off as infrequently as possible, which means having a good thermal mass inside the unit and using as large a differential as possible. So that when it does come on it runs for a longer period of time, but it comes on less often.

What is happening in the meat freezer is called "temperature glide". It has to do with evaporating temps and transfer. Once the temp sensor is insulated from the air in the space and reading the temp of the medium you want to cool. The compressor will cool the space below set point. You'll need to find a balance point. Wort has more weight than the air in the box. There is no such thing as residual/latent cooling. They're two different things. Residual cooling is sensible, you can sense it. It's what the T-stat adjusts to and what the thermometer shows. The word late is in latent and that's about it. Latent is the energy hidden in the air being cooled. Latent is in the form of water vapor. The water vapor (latent) has to be removed first, before the air can be cooled. Adding a 50 - 70 degree thermal mass cooling load and running a freezer at high temps adds to the total heat of rejection, that the compressor has to deal with. Add to that a shortened run time. The compressor runs hotter. The pressures are higher, the amp draw is higher. The refrigeration system never has a chance to balance out.

So Vlad, what do you recommend?

Don't know if anyone is still subscribed to this or is still reading but I found a happy medium. Seems to be the ideal solution for me. The Ranco dual stage temp controller. You plug a cooling unit in one outlet, and a heating unit in another. So you're able to create a dead space between the two and run both at the same time. So in essence, it allow me to run the freezer in the summer without the temp dropping too much, but also allows me to run a heater in the winter without it getting too hot. The two units solve the issue of the temperature swings from the other... I'm quite satisfied, especially since its about 75 during the day right now and 40 at night, I can set it and don't have to worry about constant daytime/nighttime monitoring.