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Greg`s Tech blog

Building a Temperature Controller from an STC-1000

Sunday 04 of August, 2013
My son & I have been brewing beer together for 8 months now. We've been very intentional about moving slowly into the process of building both our knowledge and our brew system. As I'm already a tech geek, it is real easy for me to become a brewing geek as well and to go broke in the process. When we started collecting brewing equipment, I agreed to try to buy everything half price. Home Brew Findshas been invaluable when looking for the cheapest way to solve a brewing problem.
With the summer months and the need to lager a Dopplebock, I converted a 20 yr old dorm fridge into a fermentation fridge using 1.5" foam insulation.
Fermentation Fridge
Fermentation Fridge
And while this allowed me to lager, in this configuration it doesn't actually control the temperature so I went looking for a way to do that.
I settled the Elitech STC-1000 as it is a cheap alternative to the Johnson Controls controller (cache). Of course, the latter controller is a full package with power cord and power connectors for the cooling and heating units. The STC-1000 unit by contrast consists only of the controller and control panel. Oh, and it is Celsius only so you need to convert. But Google makes that easy ("convert 68 to celsius") My unit cost $35 to make while the Johnson is about $70.

To make use of the STC-1000, I had to build it into a package that allows for convenient use. Here's how I did it.

When I looked at the size of the STC-1000, it appeared the right size to fit in a standard outlet box (in the US and it was real close in size to the GFCI cutout. I bought a plastic cover to hold the GFCI and duplex outlet. I then modified to make the GFCI opening maybe 1/4" longer.

faceplate mod Mounted STC-1000


Next step was to mount the duplex outlet and wire it up. Keep in mind we need to control heating and cooling so we need to power the outlets individually. To do this, you have to break the copper tab on the black wire side of the outlet. I didn't take a before picture, but here it is after mod.
Outlet Modification

Now we can run a wire from the heating side to one outlet and from the cooling side to the other.

The other tricky piece is understanding that the STC-1000 only provides a relay service for activating the heating and cooling circuits - it doesn't actually supply power. I dealt with that by tapping the in-bound hot lead (black wire) to both the heating and cooling connectors. This is seen here with the first loop coming from the power in going to heating and the second loop from heating to cooling:
Outlet Modification

To power the outlet, I took a short wire from the heating to the outlet and from the cooling to the other outlet. The white wiring is pretty straight forward. Simply tap the in-bound white wire and connect it to one of the white lugs. No need for separate connections as the common wire is, um, common.
Finally, we add a tension-reliever to the box, run the temperature sensor through it, mount the outlet and buckle it up
tensioner Mounted STC-1000

Notes:
- I used a new orange 25' extension cord for the power side. I cut it in half and used wire from the unused half to do the wiring. I then added a new plug to the remaining cord so I had a usable cord.
- The STC-1000 was $19, the extension cord - $10, the box and cover $6. So this controller cost $35 plus two hours labor.
- Here is a wiring diagram
Wiring Diagram