STC-1000 wildly inaccurate temperature reading

[kombat]

Just wondering if anyone else has encountered a similar issue with their STC-1000. I've been using it for quite some time with no problem. However, recently, I've used it to control the temperature of a Czech Pilsner I've been fermenting. I had it set at 54 F for 2 weeks, then I bumped it up to 64 F for the D-rest.

However, I came home tonight and the STC-1000 read 118 F. Of course, I panicked and ran over to the freezer, which was running full blast. The beer was in fact very cold, but not yet frozen. The probe was inside a thermowell, deep inside the carboy, and the beer was obviously not at 118 F, despite the fact that that's what the STC-1000 was reporting.

Has anyone else seen this issue before? Is this a problem with the probe, or the STC-1000 itself? Is my unit hosed? Do I just need a new probe? Is it a connection problem?

 

[microbusbrewery]

Probably a bad probe. I've never experienced that with my STC, but I recently purchased a single stage Willhi temp controller for my beer fridge (it looks exactly the same as an STC, but the features/programming are slightly different). It worked great for a few weeks then I started noticing it was reading a few degrees high. The discrepancy got a little bigger every day until it was reading about 50 degrees off. I contacted the guys I bought it from and they sent me a replacement probe and it's been working great ever since.

 

[TallDan]

Bumping a bit of an old thread, but I had a very similar thing happen to recently. I had two imperial stouts fermenting in my stc-1000 controlled chamber (upright freezer). Checked on them and saw the temperature reporting something like 26C when it was set to 16C. Opened the freezer to find the fermenters near freezing. It was late in the evening, so I unplugged everything and put the fermenters in the basement outside of the fermentation chamber.

The next day, it seemed to be working fine, and i started to question whether the probe was really a problem or if it had just been outside the freezer (since that temp would have been believable for garage temperature.)

A few days later, i decide to take a look again, and see the same high temp reading, but as of right now it seems to working correctly again.

So, question for the OP, ever figure anything out with this? I'm tempted to just buy another temperature controller at this point...

 

[kombat]

I had a similar failure with one of my STC-1000's. It worked fine for a while, then one day the probe reading was WAY off from the actual temperature. I swapped the unit out with a spare, and the problematic one has been sitting on my shelf ever since. I'm afraid to trust it again. If anyone ever figures out why these units do this and has a solution (replace the probe?), I'd love to hear it.

 

[day_trippr]

If you have two units, why not swap the probes now and figure out what's up?

Cheers!

 

[kombat]

LOL! I just noticed I was the original thread starter. TallDan brought it back from the dead, and I basically just repeated myself.

I guess I could swap the probes, but that would involve opening both units, unscrewing and rescrewing a bunch of stuff.. I guess the answer is, "I'm lazy and what I have right now works."

 

[Yeastacular]

I just had a similar problem, but it was with two of them. One read over 100 degrees and froze my lager. I swapped it out with a unit that was controlling another fridge (working fine). When I checked the next morning the new one was reading 116 and the lager froze again.

I'll work on troubleshooting, but if anyone has a tip, I'd love to hear it.

I was curious if it's not rated for as high of wattage as the freezer consumes, would it behave this way?

 

[TallDan]

Fairly sure the relays in them are rated for loads we're using. Maybe it's a heat issue though? Higher load may increase heat. I never saw this issue with my old fermentation chamber, but my new one would certainly be a higher load. It's also in the garage now, (was in the basement before and i saw the issue when ambient temps were fairly high...

 

[microbusbrewery]

I just had a similar problem, but it was with two of them. One read over 100 degrees and froze my lager. I swapped it out with a unit that was controlling another fridge (working fine). When I checked the next morning the new one was reading 116 and the lager froze again.

I'll work on troubleshooting, but if anyone has a tip, I'd love to hear it.

I was curious if it's not rated for as high of wattage as the freezer consumes, would it behave this way?

Might be a dumb question, but did you swap out the probe in addition to the unit itself, or did you just swap out the unit?

 

[Yeastacular]

Might be a dumb question, but did you swap out the probe in addition to the unit itself, or did you just swap out the unit?

I swapped out the entire unit (probe, display, cords, outlet). None of the same parts as the original.

I have a third that I'm going to swap probes and see if that affects it.

 

[TallDan]

Ugh. Mine was working fine for a week cold crashing a blonde, brewed an American wheat today and it's acting up again.

 

[TallDan]

Based on some testing with a DMM, it seems like the temp probe is not the issue, and that it's the STC itself. Guess it's time for a new one or an itc-308...

 

[StainlessBrewing]

Anyone ever have this issue? Temp is reading correctly and currently on heat but the fridge is still running. There is nothing hooked up to the heating side at all and I can't get it to do it again intentionally. I heated up the probe, cooled it down and the fridge shuts off. This has happened a few times and it seems like it never completed the switch to turn off the fridge once it reached the temp.

 

[day_trippr]

Did it ever work properly?

I've seen similar behavior when a duplex outlet was wired to the two relays but the hot-side bridge wasn't snipped. That connected the Hot and Cool relay outputs together, so if either was active, anything plugged into either duplex socket would turn on.

But if that's not the issue, either relays are sticking closed or the "brain" has lost its mind...

Cheers!

 

[laredo7mm]

Anyone ever have this issue? Temp is reading correctly and currently on heat but the fridge is still running...

I had something similar happen the other day, but not with an STC, but instead on my BrewPi. I only mention it because I think the STC and the little relay board I bought probably use the same 10A relays.

Anyway, my kegerator seemed to be running for a long time so I checked the BrewPi web interface and it said it was not cooling. I went over to the kegerator and the relay LED wasn't on, but the compressor was running. I unplugged the compressor and plugged in a fan, and the fan ran. I unplugged the fan, smacked the replay a couple times, plugged in the fan, and it didn't run.

It was like the relay was stuck in the closed position. I am using a 1/3 HP compressor and evaporator from a vending machine in my set up that has an 8 amp current according to the name plate. I have measured 7 amps on start up and it settled down to about 4A when running. I am wondering if the start up current is too much for the little 10A relay to handle. It has been running fine for the last two months so maybe the relay is slowly degrading.

Long story short, I switched to a spare relay board and ordered a 25A SSR and heat sink. I don't want the thing to get into that runaway condition again, especially when I am not home. The air temp in the fridge when I caught it was at 19 °F. A few hours at that temp will start freezing and breaking things.

 

[StainlessBrewing]

So far so good and the meads are still bubbling away. I've been using this controller for about a year now. It seemed to only do this 2-3 times and it's only when the fridge was off for awhile and then plugged back in. I think a relay might have been stuck but it's all good for now.

 

[Smellyglove]

I've found out that one of my STC1000+ controlled fridges is weird. It's the probe. When I touch the cable to it the temperature starts to fluctuate. Mostly stable, but still. I set a hefeweizen to 22C, and the display showed 24C, so I opened up the fridge and checked the probe, then suddenly it dropped down to 22-ish. If I bundle the cable to the probe it starts acting up. Anyone had this issue before? New probes are allready ordered, but god knows what temp I fermented this beer at.

 

[augiedoggy]

Something I have found recently in regards to the probe that may be effecting some of you. While I no longer use my stc1000+ units in fermentation controller I do still use the stc thermistor temp probes with the bru control system I built and have noticed the rubber insulation seems to be drying up allowing cracking and breakdown in the area at the top of my thermowell where the wire exits and folds over... anyway this had started to cause intermittent shorting and required a rewire to correct the issue..

In short, the wire insulation on these probes appears to be some sort of low quality stuff that breaks down and hardens over a short period of time.

 

[ScrewyBrewer]

I had the same issue with my STC1000+. I resolved it by soaking the thermowell in PBW then using a small brush to remove the gunk that had built up inside. Once the inside of the thermowell was rinsed clean and allowed to air dry the temperature readings were accurate again.

The silicone plug that shipped with my controller has two holes in it. One for the thermowell and another for an airlock. After years of use the overflow from the airlock dripped inside the thermowell and over time a thick layer of goo built up inside it. Now that everything is clean and dry it's been working good as new again.

 

[Smellyglove]

I think I wrote my last post prematurely. I took another look at the wiring and it seems by now, that one of the leads were a bit loose in the STC. I've tried wiggling the cord after tightning it and it seems stable at this point.