STC 1000 "Ebay" Temperature Controller Build

If you have an in-line fuse (like you should) you have nothing to worry about.

 

Kinda an off the wall question/thought. I have been using my ferm chamber for about 6 months now. I am also aging some beers and wine(in carboys) in the chamber. It occurred to me (unless I am mistaken) as Co2 fills the chamber it should help protect my aging stuff right?

 

It can still spark with a fuse or breaker. Just not a good practice

 

Sure, and just about any material is flammable to some point. A cigar box should be fine. I wouldn't worry about it. Just do it right the first time.

 

The flammability of an old dried out cigar box versus an electrical junction box are a bit different And doing it right the first time doesn't mean anything when you're working with cheap unreliable screw terminals on the stc1000.

 

This is true BUT! Who uses an electrical junction box for this project? Seems a bit overkill to me (and it doesn't look as cool as the cigar box). Just keep an eye on your connections every now and then and make sure nothing is shorting out. Cheers to innovation.

 

I have been trying to think of a liner that could go in the box and make a little more fire resistant. Fiberglass can be time consuming and the other options are too $$$.

Check your smoke detectors function and go with it.

 

There's a thin lining called formex made for this type of thing. It's a flame retardand polypropylene which you can cut to shape. itwformex.com

 

The wooden box is probably OK, just not my choice.

Me. I really like "overkill" safety with 120 or 240VAC. Our house was wired creatively by the previous owners. A loose screw (literally) on an outlet and all the lights went out and the offending outlet melted. We wuz lucky it stopped there.

So color me nervous. No worries. I will go with PVC or steel J-boxes designed for the purpose. A 3-gang box will fit the controller and 2 outlets. Other project housings are OK.

A proper enclosure will not stop damage from bad work, just slow it down.

 

Just pulled the trigger on my first STC-1000 (currently $19.28 on Amazon). Going to use the above-referenced .pdf as my guide. I notice that his wiring diagram includes a 10A fuse, but his parts list does not.

What's been the general experience of other STC-1000 users? Is the fuse needed? No?

I will be using this in my ferm chamber (an old top freezer/bottom fridge refrigerator). The outlet I have the current analog controller and fridge plugged into is a GFI, if that makes a difference.

Full disclosure. The fridge is very old and does have a loose or bare wire somewhere. If there is too much other load on the circuit, it's been known to trip the GFI. For the most part though, it operates fine in my garage as a ferm chamber when I have a batch going, and beer cooler when I do not.

 

Any fuse holder rated for for 110v+ from Radio Shack should work. You will just put a 10amp fuse in the holder. Here is one for $3.49 on radioshack.com.

 

One other question. I am looking into a thermowell for my fermenter as well. Does anyone have the diameter on the sensor probe that ships with the STC-1000? I have 2 choices in the thermowell I am looking at. I can get one with a .25" diameter or a .3" diameter. I'd like to go with the smaller one if the STC-1000's probe is going to fit.

 

Do you mean the plastic one or the metal one? There are two different probes that could potentially be shipped with the STC-1000...

The plastic one I have here has a rectangular profile with rounded edges, 6mm x 4.5mm (1/4 x 3/16 inches?). I'd cut 6x5 mm to be safe.

The wire itself is 4 x 1.5 mm (maybe cut 4x2mm to be on the safe side?)

Lee

 

I use a Brewers Hardware 16" straight wall thermowell for my STC-1000 with black plastic sensor.
http://www.brewershardware.com/16-Stainless-Steel-Thermowell.html
ID = .305"
OD= .375

 

I took a chance before the STC1000 got here and ordered that same thermowell yesterday. The controller arrived last night and I measured the black plastic sensor to be .25". So I should be good to go with this thermowell.

 

That is really neat, because the probe that comes with it isn't good for much, frankly!

You just insert the probe in the stainless tube and seal it somehow? Do you have to recalibrate the STC-1000?

 

The stainless tube is open at one end and sealed at the other. You insert the closed end into your fermenter (many will use either a rubber carboy stopper with an extra hole drilled in it, or the second port on one of those orange carboy caps)

That leaves the open end of the tube accessible from outside of the fermenter. You just slide the temp sensor down into the tube. This allows the probe to be surrounded by your fermenting beer, giving you more precise control of your ferm temp. By being inside the beer, your STC1000 turns your heating and cooling devices on/off depending on beer temp, not ambient air temp

 

FWIW many people have found that it actually creates less accurate temp control. Because there's so much thermal mass, and it takes a long time for the heat to transfer to or from the center of the beer, using a centrally located thermowell to control temps often results in significant overshoot and wider temp swings. Taping the probe to the outside of the fermenter and covering it with some insulation generally provides much more stable temp control when utilizing simple on/off controllers like the STC-1000. The most accurate and stable temp control would be using a thermowell and a PID type controller.

 

Of course you'd tell me that after I order a thermowell

 

I guess could try both methods and determine which works best

 

I've had good luck with taping bubble wrap over the probe on the middle of the side of the carboy

 

From a "gut feeling" perspective, it doesn't feel right that a probe immersed in the liquid would be less effective than a probe outside the carboy. I understand the temp of a larger volume of liquid changing more slowly. But wouldn't the natural currents in the beer, along with those caused by the agitation of fermentation effectively mix the beer, causing the temperature to stabilize throughout the carboy?

I am putting together a whole system with the fridge, an STC1000, a thermowell and a heat source. It shouldn't be too hard to do a few tests with just water in a carboy to see which method proves more stable.

 

The issue is alleged.. The freezer cooling system runs until temp sensor in the center of 5 gal of liquid reaches the target temp.

At that point the freezer has cooled the chamber and most of the liquid to a temp colder then the target temp.

No idea who makes this claim,,,,, but it's not I.

<My STC-1000 set to the smallest differential, and target temp of my desired set point holds to within a deg.
Thats an STC-1000 sensor in a 16" thermo well, sunk mid way in a 6.5 gal bucket containing 5 gal of wort (beer).

YMMV, but it works for me.

Oh and the whole deal about fermenting beer being higher by up to 10 deg has not proved out either with my last three batches. Perhaps the temp differential is more significant in non temp controlled high ambient temp fermentation situations. (like trying to ferment in a 70+ deg area using a very aggressive yeast)

 

I would think over cooling would be less of an issue in my set up as I use the refrigerator compartment of a traditional freezer top fridge bottom refrigerator. The temp of my fermenting beer changes slowly. I usually chill to 3-4 F below my desired ferment temp and use my analog controller to control the top end temp. I am using the STC to add a heat cycle to my set up so I can continue to ferment in the garage through the winter months.

 

It's not just an alleged issue, it is a very real phenomenon that many people have witnessed first-hand. I have a DIY thermowell I made out of a damaged corny diptube, and have tested several probe placements myself. The temp of the wort during active fermentation will be relatively homogeneous due to the churning action of the yeast, so it's not that the wort near the edges of the fermenter gets colder. In this case, it's just the interior of the ferm chamber and the fermenter itself that experience the initial overshoot, which is then transferred to the wort. Depending on the thermal mass and specific heat of these items, it can transfer a substantial amount of heat, causing an overshoot of the wort. My experience with sankey keg fermenters showed a temp overshoot of several °F using the thermowell placement. I would imagine someone fermenting in plastic buckets would see much less variation since they have considerably less thermal mass than a sankey keg.

FWIW the biggest difference is witnessed when changing temps. Once the wort is at the set temp and the temp differential is relatively small, the thermowell placement results in pretty stable temps (although not quite as stable as taping to the outside of the fermenter). When trying to get down to ferm temps from a higher temp, or ramping up temps towards the end of fermentation, or cold crashing however, the temps yo-yo significantly for a long time before finally settling. The larger the difference between the wort temp and the set temp, the worse the temp swings are.

I'm not trying to suggest that using a thermowell for controller probe placement doesn't work, or is going to cause major issues. It works fine for many people, and any temp swings it causes usually aren't significant enough to be problematic. I'm simply relaying my experience that it's not quite as accurate as other methods in some cases.

The most I've seen was 9°, and that was on my first batch before I had a clue about proper ferm temps or ferm temp control, and the ambient temp was in the mid 70's. The fusels that Nottingham throws at those temps render a beer nearly undrinkable. With the tightly controlled ~63-65° ferm temp I use for most of my beers, it's generally only a couple of degrees.

 

I found stc1000s on newegg. Ship from the states for the same price.
Prost.

 

Those are Newegg Marketplace sellers, so who knows where they ship from. I noticed the first one also sells on ebay, amazon, etc.

Still no Fahrenheit either :-/

 

Just stick a carboy thermometer on all your carboys. Now you have a double check for your thermostat AND a F to C conversion chart.

 

Oh I didn't notice that.
Yea but F to C and back isn't a terribly huge headache.

 

Good point!

 

IMO, those provide poor accuracy during a cooling or heating cycle, since they are not thermally isolated from the chamber air. In-between cycles they are fairly accurate. YMMV

 

The STC 1000 I got this week (from one of the amazon links earlier in this thread) appears to have shipped from Las Vegas.

 

I have bought three STC-100 From three different Amazon retailers.

One shipped from China direct, two came from US locations, ALL THREE came in the same packaging, not just the OEM inner cardboard box, but the same plastic tape and outer overpack.. leading me to believe, they all started at the same place,,, and a US retailer is just ordering in bulk, and reshipping.

 

Regarding the issue of measuring beer temp instead of ambient temperature in the fermenter, I have one I made using a mini-fridge.

I tried my setup first with the probe wire taped to the wall and the probe in open air. The heating and cooling cycled continuously. The compressor would come on, the temperature would drop, and when the compressor shut down the temperature would keep dropping until the heater (a 60-watt ceramic heating element) kicked in. When the heater turned off, the temperature would keep rising until the compressor turned on again...

I tried dropping the probe directly into a 2 quart tea kettle set in a corner behind the carboy. It slowed the cycling down, but didn't stop it. So I taped the probe directly to about the middle of the carboy, and covered it with a good-sized piece of foil-covered bubble wrap (about 8"x8").

End of problem; the temperature normally overshoots the set point by 0.1*C; once in a while it'll go 0.2*C past it. I suppose if I made a large change in a short time, things might be different. But I normally raise or lower the temperature 1 or 2 degrees C at a time, and let it stabilize for at least a few minutes before going farther..

 

I'm trying to understand why a thermowell into the middle of the beer would cause cycling. Normally, thermal mass is your friend if you want steadier temperatures. And although liquids sometimes stratify vertically, I seriously doubt you'll find a measurable difference between the temperature in the center of a carboy vs. temperatures at the sides.

I can think of only two possibilities so far: one, the metal thermowell is conducting ambient temperatures to the probe at its end faster than the beer can heat or cool it. Doubtful, but I guess possible. The other, more likely possibility is that there's enough air circulation in the thermowell to mingle with the ambient air outside it. If that's the case, closing the upper end after the probe is dropped into it should take care of the problem. Shouldn't take much - silicone, bubble gum, a piece of tape....

 

I don't have direct experience but have studied a lot of engineering physics. I would expect this issue would be prevalent in systems with a high thermal mass besides the carboy itself. What's happening is that in order to get the liquid down to temp, the fridge would need to stay on until the temperature at the probe is satisfied. But at that point, the rest of the mass is at a high temperature differential to the carboy. (The walls and internals of the fridge are a lot colder than the carboy.) So when the STC shuts off, the temperature continues to coast down, and then the STC will turn on the heat to compensate. I think by taping the probe the way you did, you found a happy average between the thermal mass of the carboy and that of the cooling agent. It's the same for heat of course.

 

I think that with the fairly big patch of foil/bubble wrap insulation over the probe, the temperature read I get is actually for the beer itself. Of course my 5 gallon carboy is in a very small converted fridge, one that doesn't have enough thermal mass of its own to sneeze at. In fact, when the carboy is full it weighs more than the entire fridge does - including the compressor.





The insulation on the door is there because I had to notch through the insulating foam inside after I removed the door shelving, to make room for the carboy. I ordered the fridge online from Walmart sight unseen, and it turned out to be smaller inside than the one I measured at work - which is the same size outside, but loses less depth inside to the compressor unit. But for $99.00 with free delivery, I'm not going to complain.


The pic's are from before I installed the heater and my STC-1000 build.

 

I bet you're right - there isn't much thermal mass of that small fridge, and a lot of it's plastic. Plastic has a very low thermal conductivity as well. I am using a fridge that is large and has lots of metal lining the inside. I'd be willing to bet that the 'coasting' would be an issue, but the effect would taper off as the whole shebang reached target temp, since all that mass would hold temp very well.

 

I think you mean in systems with a high thermal mass besides the wort. The fermenter also has a lot of influence. And it's not just the thermal mass, the specific heat of the materials is a significant factor too. A sankey keg fermenter in a full size fridge with heavy shelving and a few six packs of other beer will have a lot of temp carryover when there's a significant temp differential. A better bottle fermenter in a mostly plastic mini-fridge with nothing else in there will not.

 

Off topic (kinda)

I still wonder about the difference some people report between thermowells and taping the probe on the side. What I am about to say is based purely me thinking it through with whatever common sense I possess. I have no science to back this up.

Is it possible that the "overshoot" in temp is caused primarily by the fact that some people use a chest freezer for a ferm chamber, while others use a refrigerator? I would think you would have the opposite problem of an overshoot when using a chest freezer and taping the probe to the outside.

Think about it this way. If you put the probe in a thermowell, the thermal mass prevents the controller from turning off, because the temperature of the wort at the core takes longer to change temp. Therefore the freezer runs longer, holds its own temp better, and by the time the beer at the core of the volume hits the set temp, the beer on the edges has chilled below the set temp, causing an overshoot of the entire volume as it reaches a temperature equilibrium.

If you were to take the same wort, in the same chest freezer, but tape the probe to the outside of the fermentor, your compressor would shut off when the wort on the edges of the fermentor reaches set temp. This would mean that the same wort at the core that was more resistant to temp change before, is still resistant to temperature change now. It would still be warmer than the set temp. Partially because it is fermenting, and partially because it no longer has the compressor's cooling power acting on it. If you do not place your wort in the chamber at or slightly below your desired fermentation temp, I would think that this method would take you longer to get there.

So to me, the discussion shouldn't be thermowell vs. taping the probe on the outside. It should be rather, which type of fermentation chamber provides the most consistent cooling?

For me, even with my old analog Johnson controller, I have seen more consistent results by cooling most beers 3-4 F below my desired fermentation temperature before pitching yeast. By whirlpooling my wort and recirculating ice water through my immersion chiller, even on the hottest summer days I can get my wort below 65F. I usually pitch about 60-62F and let my beer free-rise over the first several hours.

That, combined with using a refrigerator vs. a chest freezer, seems to allow me to make gradual temperature changes. Mind you, my thermowell is still in transit so I have been doing this with an old Johnson analog capillary probe taped to the side of a better bottle. So I am only speaking speculatively with regard to a thermowell.

But It makes sense to me that the the starting temperature of your wort and type of chamber you're using would have more to do with over (or under) shooting your temp than whether you're using a thermowell or taping your probe on the outside