Fermentation Fridge Quandary

[MartinOC]

Yesterday, I hooked-up a single-chamber fridge (ie. no separate freezer compartment) with an STC-1000 (wired it up myself & tested functionality - all good), fitted a heat-pad in the door, put a full 25L cube inside (temperature probe taped to the cube, covered by an old stubby-holder) & set it to 18C. All sweet after a few hours.

I then decided to find out just how low I can get the temperature (for cold-crashing & lagering purposes). I turned the fridge to it's coldest setting (still controlled by the STC) & set the desired temp. to 1C. That was 7am today.

Up until now, it just won't go below 8C.

I've tried turning the whole shebang off, figuring that the compressor needed to take a rest (it actually stopped of it's own accord earlier), then turned it on again (showing internal 9.5C), but even so, 7.8C is the best I can get. That's not good for a domestic fridge that would need to maintain at least 4C for food-safety.

So, a few questions of the more experienced in these dark-arts:

Am I perhaps asking too much of the compressor in one go (ie. should I be ramping-down in 1-2C increments every few hours/days)?

Do fridges have some sort of "I've had enough for today, so I'm not going to play" failsafe/timer mechanism built-in that the STC can't control?

Would a cold-crash from ale temps to 8C be enough to achieve the desired effect?

Anyone else experienced this kind of thing before?

The fridge cost me nothing & if this is the best I can get from it, it's not a huge problem, 'cos I'm mostly an ale-brewer/drinker.

Your thoughts/experiences & input/feedback would be greatly appreciated....

 

[O-beer-wan-kenobi]

Is the temperature controller wired into the fridge thermostat circuit or does it switch power to the fridge?

 

[MartinOC]

It switches power on/off to the fridge via the STC. I figured that as long as the desired target temp. hadn't been hit, it would continue to make demands of the compressor to get colder....?

 

[Dan Pratt]

you will still need the dial on the fridge thermostat on 5 or 6 or on high to get it to go cold. If its only set to 1 or low then thats all the compressor will do.

I have mine set to 5 and that gets it to cold cond temps no worries.

 

[O-beer-wan-kenobi]

It could be the fridges internal thermostat that stops it from getting the temperature down. It could be faulty or it may see the internal temp at 4 degrees (usually the lowest temp a fridge can be set to) but the insulated probe on the cube sees the temp higher. It may just take some time for the cube to catch up and equal out the temp.
You can link out the fridge thermostat or wire it into the controller depending on the type of fridge you have. Obviously you need to be qualified or get somebody qualified to do it.

I'm not saying this is the problem but it could be.

 

[krausenhaus]

Sometimes mine still tends to be around 8ish degrees at the 12-hour mark, but gets down to temp after another 8-10 hours. It does seem to pack it in and take a breather for a while like you describe, so I'm assuming its some sort of overheating protection or something.

 

[mxd]

if the fridge thermostat on coldest and you can't hit the temp then the fridge is stuffed.

 

[MartinOC]

Thanks guys, you've given me more food for thought.

For now, I think I'll sit on it overnight & see if it's just thermal-lag from the cube, or a potential fault with the unit (which frankly, I don't intend spending $'s on fixing).

Like I said, it's not the end of the world if a free fridge won't give me the cold-shoulder....

 

[Camo6]

Sounds like it's on the way out. I've had a couple of fridges go the same way and it seems cheaper to replace them then fix them. Even the free ones!
You could let the probe hang away from the cube just to see what the ambient temp gets down to without waiting for the cube to catch up.

 

[Yob]

Had the same issue, disabling the fridge thermostat will make it spunky.. Will try to dig up the thread that I got advice on to do so.

Cheers

 

[drifting79]

I have a pretty modern fridge
I gutted the internal draws and air channeling parts then disconnected the temp sensors
It tends to stop for 10 min at where ever I have it set to . Currently at 2 deg for ccing but after a day it has kinda found it self and is working fine




Sent from my iPhone using Aussie Home Brewer

 

[MCHammo]

My fridge was doing the same thing when I got it a few weeks ago. Got down to 12C in no time at all, then took several hours more to hit 8C, and about another day to hit 4. On about the third or fourth day it managed to hit zero. It's entirely likely that it was overheating and needed a rest, or it had inbuilt protection to prevent such an occurrence. Mine also has a freezer, so that could have been a problem for me (freezer reaching temp or defrosting, etc). It's working fine now, though I do have some mods planned down the track...

 

[GalBrew]

Sounds like that means your brewing hiatus has come to an end then? When can we expect the first brew?

 

[MartinOC]

Sounds like that means your brewing hiatus has come to an end then? When can we expect the first brew?

Take a place in the queue, pal!!

I owe SWMBO's uncle beer for a new motor for my grain mill & more beer for an old CUB 18 Gallon keg & yet more beer for other bits & pieces (with beer-"interest" for his patience). Then I have to get the plumbing bits to update the whole system & drag it out of the stoneage....& into the HERMS-age. This forum has been great for getting inspiration & information.

....but yeah, I am ACTUALLY brewing again (Geez! It's only been 10 years!). Right now, I've got a yearning for a Saison, but the Uncle wants a 6+% Porter.

I'll get there (eventually!!).

Update: The fridge is currently running at 4.7C

 

[punkin]

I'd be disconnecting the fridge from the STC and plugging it into the wall if it kept happening, but sounds like it's resolving itself. Definately seems like a conflict between the fridge thermostat and the STC probe. The thermostat is measuring the air temp (or wall temp) and turning the fridge off while the STC wan'ts it to keep running.

The box of water will eventually catch up, but it will only get down as far as the fridge thermostat will allow it if you know what i mean.

Agree with those who say disconnect the thermostat.

 

[MCHammo]

One of the mods I want to perform is to replace the thermostat with my own temp controller. Will switch the fridge on and off the same way the thermostat does, but using my own microcontroller, temp probe, etc. No more STC1000 then. Could easily run different temperature profiles automatically, log data, etc.

 

[Ducatiboy stu]

Thats actually realy easy. I would replace the fridge thermo with an stc etc. But not everyone can do that.

 

[MartinOC]

I'd be disconnecting the fridge from the STC and plugging it into the wall if it kept happening, but sounds like it's resolving itself. Definately seems like a conflict between the fridge thermostat and the STC probe. The thermostat is measuring the air temp (or wall temp) and turning the fridge off while the STC wan'ts it to keep running.

The box of water will eventually catch up, but it will only get down as far as the fridge thermostat will allow it if you know what i mean.

Agree with those who say disconnect the thermostat.

Yep! I'm absolutely with you on all of that. Logic prevails. I'm going to see how far the unit itself will go first over the next few days before getting drastic.

 

[Kingy]

I'd run it without the controller to see how low it goes. Some controllers also have a compressor rest period set as factory settings. I'd also just sit the probe at the bottum next to where the cube sits. No big deal. Good luck with it.