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Old 10-26-2013, 03:22 AM   #1
Aug 2013
Kalamazoo, Michigan
Posts: 21
Liked 9 Times on 5 Posts

In this thread I will describe the steps I took to replace the stock temperature controller that came with my Chest Freezer with an aftermarket controller. Most of the temperature controller threads I have seen involve creating an outlet that the controller turns on and off, plugging the freezer into that outlet, and then hanging the probe inside the freezer. My preference was to utilize the existing space to create a cleaner and simpler design. I initially intend to use the freezer as a fermentation chamber, and have future plans to modify it further into a Keezer. The steps I took for this project were gathering supplies, removing the old controller, and installing the new controller in its place.

Step 1:Supplies
  • Chest Freezer (Mine is a 7.0 cubic foot GE Chest Freezer (model FCM7SUBWW).

  • 12 gauge stranded copper wire
  • Twist-on Wire Connectors

Step 2: Removing Old Temperature Control
First I removed side vent, which let me access the clips on the back of the front face plate. I removed the clips, and was able to detach the face plate from the freezer. The connection I had to unplug were the positive/negative for the ‘Power On’ light (Red/Black & White/White), the positive/negative for the temperature control unit (Red & Black), and the natural ground (green).

The only connection left was the temperature probe, which came inserted into a plastic tube into the bowels of the freezer. I pulled this out and removed the entire controller. This left a hole in the front of the freezer where the previous controller and faceplate were.

Step 3: Installing the New Temperature Controller
The first task was to remove the connectors from the ends of the wires for the old controller, which looked like this:

I cut them off and stripped them. Next I cut four 6” lengths of wire, stripped them, and inserted them into the new controller. I now had bare wires coming out of the freezer, and bare wires coming out of my new temperature controller. All that was left was to connect them. This diagram outlines the connections I made.

Using the stencil that was included in the instructions, I measured a spot for the controller on the lid of the junction box. I cut out the stenciled shape with a coping saw, though a Dremel or other power tool would have been much easier. I set the junction box lid, now my new faceplate, into place and primed the screw holes with a drill. I inserted the new controller into the freshly cut lid, and connected the loose wires to the freezer’s wires using the twist-on wire connectors. I inserted the new temperature probe into the plastic tube that housed the old probe. Before I screwed the new face plate onto the freezer, I tested to make sure everything was working properly.

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Old 10-26-2013, 03:28 AM   #2
NTXBrauer's Avatar
Sep 2013
Dallas, Texas
Posts: 1,139
Liked 152 Times on 117 Posts

Nice job. I built a temp controller, with an external utility box, using the same digital controller you have. I like how you were able to integrate it into the front of the freezer where the original control panel was.
"A fine beer may be judged with only one sip, but it's better to be thoroughly sure." -Czech Proverb

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Old 10-26-2013, 02:23 PM   #3
Jan 2011
Pittsburgh, PA
Posts: 1,538
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Nice job. Does that controller allow you to set a temperature range to prevent short cycling the cooling unit?

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Old 10-26-2013, 08:16 PM   #4
Aug 2013
Kalamazoo, Michigan
Posts: 21
Liked 9 Times on 5 Posts

Thanks for the feedback!

@Seven: Yes the controller does allow you to adjust the temperature range. The default is 2 degrees, but I upped mine to 3 degrees to reduce the number of cycles. It also lets you specify whether its heating or cooling, delay the start, and offset the temperature for any corrections that may be needed. Here is the Diagram that comes with the unit.

CP is the temperature range, i've heard this referred to as the hysteresis cycles, but the manufacturer classifies it as "Slewing Range".
CA is the temperature correction, I have mine set 3 degrees, because my probe is built into the wall of the unit, not hanging free in the freezer.

Hope that helps, it's an amazing unit for the price. You could defiantly get a higher quality one with more features, but at $14.66 you can't lose.

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Old 10-26-2013, 08:28 PM   #5
dbrewski's Avatar
Oct 2011
Posts: 1,011
Liked 52 Times on 46 Posts

Well done. I have a Frigidaire I want to use as a fermenation chamber and a very similar controller. This is a very clean way to do it, hope I have the same panel.

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Old 10-26-2013, 08:59 PM   #6
Oct 2013
Twin Cities, MN
Posts: 179
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Nice work, thanks for the write-up!

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Old 10-26-2013, 09:08 PM   #7
Aug 2011
Montreal, Quebec
Posts: 209
Liked 13 Times on 11 Posts

I did the same thing with mine, but I haven't added a nice plate like yours (haven't got to it yet). The temp controller is just hanging out in the opening for now. The only problem that I have without the added heat source is that sometimes it gets too cold when I am lagering. If the temp is set very low the compressor will come on and end up dropping about two degrees lower than what I set it. I think maybe the censor recognizes that the temp has reached the target but because it is a new unit the combination of the compressor working very hard and the insulation ends up dropping it a bit lower.

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Old 10-30-2013, 03:34 AM   #8
Aug 2013
Kalamazoo, Michigan
Posts: 21
Liked 9 Times on 5 Posts

@Oddball: I believe the way this unit (and the STC-1000) works is that it cools/heats until the probe reaches the set temperature. I know this sounds obvious, but if you have your controller set to 34 degrees to lager, the compressor will be on full blast until 34 degrees. This may account for the temperature dropping below freezing. I suggest initially setting your controller to a higher setting (40 degrees?) and then dropping it down in the increment that your "slewing range" is set to.

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Old 12-02-2013, 09:09 PM   #9
Nov 2013
Posts: 22
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new poster to homebrewtalk here. I've read many posts on how to install one of these STC-1000 and, until this thread, it has appeared that people have been adding an STC-1000 to work in tandem with the existing temp. controller. So the STC-1000 will tell the existing controller when to turn on the compressor.

It appears your method is to remove the OEM temp. controller altogether, and simply install the STC-1000 as your sole temp. controller. So my questions:

1) Am I correct in what I am seeing here?
2) Am I over-thinking this? This method seems way more simplistic than using the STC-1000 in tandem with the OEM temp. controller. Why don't more people do this?
3) What are the pros/cons of this method vs. using the OEM temp controller + the STC-1000?

I should note that I'm only interested in cool temps to chill my beer, not heating the unit.

Thank you!

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Old 12-03-2013, 02:14 AM   #10
May 2011
Stow, MA
Posts: 17,824
Liked 3074 Times on 2300 Posts

fwiw, I'm pretty sure a wire is transposed in the "after" diagram.

The black wire from the plug should be going to the controller pins 3 (power) and 1 (or 2) for the relay to the compressor. The other black wire should go from the relay pin 2 (or 1) to the compressor.

As drawn the controller would never power up...


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