STC-1000 Issue

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petrolSpice

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Last night I decided to move my fermenter out of the chest freezer fermentation chamber. The temp was holding steady at 19.9C before I moved it. I turned off the STC-1000 and unplugged the sensor, then moved the fermenter from inside the freezer to on top of the freezer. I plugged the sensor back on and turned on the STC-1000 and now it was holding steady at 20.6C...

According to the controller moving the fermenter a couple feet raised the temp by 1.3F...

About an hour went by and I heard a *click* from one of the relays in the STC-1000, I look over and the temp shot up to 21.5C. I kept an eye on it and the temp was bouncing all over from 20.6C up to 22.1C. Occasionally it would settle back to 20.6C for a minute or two then start oscillating again.

I turned the controller off overnight because it clearly wasn't going to be reliably holding the temperature. I turned it on again this morning and the temp held steady at 19.8C for about an hour before I turned it off and left for work.

My temp probe is ran through the blowoff tube and dangles down into the wort right in the middle. I did calibrate it with ice water and ended up with a -0.7C calibration value. I've been using it like this for a few batches now without issues. I ordered 5 more temp probes from Digi-Key to see if perhaps the probe is the problem.

Anyone had a similar problem?
 
THis may be a simple question, but are you submersing the probe in water within your fermenter? This will keep the wild temp swings in check since it is measuring the liquid temp (which is the temp you want to control).

I have a small glass of water next to my carboys that the probe rests in.
 
I think he puts it right into the wort.

Sounds like maybe your probe is malfunctioning. I know the probes are supposed to handle the wet environment, but I don't trust them for full submersion. I've had other waterproof probes go bad over the years. I use a thermowell to be safe.
 
Yes, the probe goes straight into the wort. Everyone says they are waterproof since they are meant for aquariums. They look waterproof too.

I do have a thermowell but cannot use it with a blowoff tube since I'm use carboys instead of buckets. I'll probably start putting the probe on the outside of the carboy instead of right into the wort.

The oscillating temps that the controller is showing is indicative of an electrical issue. It will swing +/- 1C in seconds, clearly its not reading actual temp. I'm thinking it's a probe issue, but was curious if anyone else had a similar issue and could tell me what their problem was.
 
....unplugged the sensor, then moved the fermenter from inside the freezer to on top of the freezer. I plugged the sensor back on ....
Is the sensor connected directly to the controller, or have you added connectors? Maybe you have a poor probe connection since that is the activity that seems to have started the performance issues.
 
Is the sensor connected directly to the controller, or have you added connectors? Maybe you have a poor probe connection since that is the activity that seems to have started the performance issues.

I have it connected to the box I built with a phone jack. I wiggled all of the wires and connections it didn't change anything. It's been working fine for a couple months, just started acting up recently.
 
I'm curious... what was the motivation to move the carboy out of the chamber? Regardless, it does sound like a probe issue, but if the temperature difference between the outside environment and inside the chamber is great, I could see actual temperature changes being the culprit.

Do some legwork and check on your connections between the probe leads and the STC-1000. Make sure they're dry and without corrosion so as to rule that out as the culprit. Good luck!
 
I'm curious... what was the motivation to move the carboy out of the chamber? Regardless, it does sound like a probe issue, but if the temperature difference between the outside environment and inside the chamber is great, I could see actual temperature changes being the culprit.

I needed the chamber to cold crash another batch. The 5.5gal batch I pulled out was through active fermentation and only needs to be kept warm at 68F with a fermwrap, it does not need the cooling capability of the freezer anymore.

The temperature outside the chamber was I'm guessing 1-2F cooler than inside the chamber. It only took a few minutes to move it and turn the controller back on, at which point it showed a temp 0.7C higher. So the change in temp the STC-1000 showed was definitely fictitious.

Perhaps there was that much temp variation in the wort itself, and moving the wort caused enough sloshing to mix it up and change the temp? I highly doubt this is the case but who knows.

Definitely looking like a wiring/connection/probe issue. I'll post up results when it is resolved.
 
I know this isn't exactly on topic...

BUT, I used to be one of those people that wanted the probe right there in the liquid. Submerse it, build a thermowell.... whatever, but man that must be the most accurate way to do it! Right?

Well after lots of testing, I now just tape the probe to the side of the carboy and cover it with a few layers of shop towel for insulation. The difference was statistically less than the precision of the probe, so I stopped fussing with the extra complexity.

If it is in fact a submersion issue, it's something to consider.
 
I had a PID start to behave like that, with very erratic +- 1 degC temperature swings at a rate much quicker than could be possible. Turns out I had a wiring malfunctioning and current leaking to earth was causing it - it wasn't enough to trip the RCD strangely.

I'm not sure if this may apply to your set up but it never hurts to revisit your wiring every once in a while anyway!

It could also be the probe, although they are supposedly waterproof as already mentioned, they can give out after a long time of immersion. You can easily and cheaply replace it with another thermistor (10k, B = 3435) if you want to rule this out too.
 
I know this isn't exactly on topic...

BUT, I used to be one of those people that wanted the probe right there in the liquid. Submerse it, build a thermowell.... whatever, but man that must be the most accurate way to do it! Right?

Well after lots of testing, I now just tape the probe to the side of the carboy and cover it with a few layers of shop towel for insulation. The difference was statistically less than the precision of the probe, so I stopped fussing with the extra complexity.

If it is in fact a submersion issue, it's something to consider.

Yep, I'm going to start taping it to the side I think. Much less of a hassle. During active fermentation I know the average wort temp will be slightly higher than the outside of the carboy, so I'll just subtract 1F or so from my set point.
 
Yep, I'm going to start taping it to the side I think. Much less of a hassle. During active fermentation I know the average wort temp will be slightly higher than the outside of the carboy, so I'll just subtract 1F or so from my set point.

If that. I was surprised to find how close it was even during active fermentation. There is a lot of convection going on so the transfer is quick. I ferment in PET, never tested HDPE or glass. But I can't imagine they would be too different. Just insulate the probe from the air in the chamber.
 
The myth of the "aquarium temperature controller" has really long legs. Probably unstoppable.

But did you ever notice neither "aquarium" nor "waterproof" appear even once in the STC-1000 manual?

Cheers!
 
The myth of the "aquarium temperature controller" has really long legs. Probably unstoppable.

But did you ever notice neither "aquarium" nor "waterproof" appear even once in the STC-1000 manual?

Cheers!

Technically, if the manual is a source of authority on these devices then they are fitted with nixie tubes ;)
 
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