For the last few years I have carried out my homebrewed beer fermentations in a freezer and managed the temperature using a Johnson Controls Digital Thermostat Control Unit (model A419) which is a single stage controller i.e. it can be used in cool mode or heat mode.
For the last year or so I have seen the price of STC-1000 All-Purpose Digital Temperature Controllers drop in price and with a fellow homebrewer completing a build of a Dual Stage Temperature Controller I decided to take the plunge.
The Johnson Controls A419 is widely used by homebrewers to control a freezer or fridge for temperature control when fermenting wort as better temperature control improves the quality of the resulting beer significantly by avoiding off-flavors caused by stressed yeast.
There are however a couple of problems which I have encountered:
- In the summer the controller usually needs to be used in cool mode whilst heat mode tends to be needed in winter. Spring and Autumn/Fall can mean switching between the two which means unscrewing the top and swapping over a jumper which can be inconvenient depending on the frequency that this needs performing.
- When using a freezer there can be a tendency for it to over cool once the sensor probe triggers that a certain temperature rise has been reached and the compressor is run for a minimum period.
The ideal solution is to have a controller with both cooling and heating power outlets that allow a desired temperature to be set then the cool and heat modes can be triggered to lower or raise the temperature respectively depending on the sensor probe reading and cater for the time of year plus any over cooling which might be encountered.
There are a wide range of resources available on the Internet regarding how to build an STC-1000 based temperature controller including instructions, wiring diagrams and videos. I will include links to the ones that I followed so as to avoid any duplication.
Note: Electricity is potentially dangerous and I am not an electrician so every care should be taken and if in doubt always consult a qualified professional to avoid any risk of injury or even death! I live in the USA so all descriptions and photos relate to my geographic location, please research how the parts, wiring etc may differ for your location.
Here are the parts that I purchased*, obtained or already possessed:
- 3-pin Power Lead from an old kettle = $0.
- Electrical tape = $0.
- 6″ lengths of electrical cable = $0.
- Wire Connectors = $0.
- Inkbird All-Purpose Digital Temperature Controller (STC-1000) = $15.99
- Hammond 1591ESBK ABS Project Box Black = $7.45
- Pass & Seymour 885TRWCC12 Duplex Decorator Tamper Resistant Receptacle 15-Amp/125-volt Side Wired or Back Wired Connections, White = $2.68
Total price = $26.12**
* as is the nature of online pricing, these can fluctuate.
** free shipping due to order size being over $35 as I ordered other items at the same time.
With the items that I already had even if you needed to buy these then the total build cost should still come in around $35-40 which is considerably cheaper than the majority of Dual Stage Temperature Controllers which retail for $140+.
The instructions I followed can be found here:
Some useful videos include:
Below are a series of photos from my build:
I found this project to be straight forward and the instructions were clear and easy to follow. My main advice is to do plenty of research and proceed at your own pace and if in doubt double-check anything before making a cut. The result is that I now have a Dual Stage Temperature Controller to power both the freezer that I use as a fermentation or lagering chamber together with a Reptile Tank Heating Mat that I use if the temperature needs raising. The bonus is that I also managed to save myself around $100 and have the satisfaction of completing the project myself.