How to Build a Fermentation Fridge – DIY Brew Fridge

The lovely long hot summer we’ve had this year has had one major drawback; I’ve not been able to brew as it’s been too warm for fermentation in the house and stocks are beginning to run low! Most yeast that you use to brew beer likes to ferment around the 20C mark, above 22C you start to get off flavours and fusel alcohol. To get brewing again I decided it was time to make a fermentation fridge.

A fermentation fridge, or brew fridge as it’s sometimes known, is just a normal larder fridge with a 1ft greenhouse heater and an STC-1000 to control the temperature. You simply set the desired temperature into the STC-1000 and it switches the fridge on if it gets too warm and the heater on if it gets too cold.

Being a bit of a novice when it comes to electronics I was slightly nervous about wiring things up (also I was instructed “not to burn the house down”) I found some great guides on the home brew forum and a clear and simple video on Youtube. These were really helpful and actually made building the brew fridge quite an easy process.

What you need to build a Fermentation Fridge for your home brew

  • A larder Fridge – I got mine via Preloved for £20
  • STC 1000 – Ebay or Amazon for around £14.50 -£20
  • 60W 1ft Greenhouse Heater – Amazon or Ebay £13-£17
  • Project Box – Maplin/Amazon £10 (lots of people use sandwich boxes for the electrical bits)
  • 3 core wire – I used an old monitor cable but it’s pretty cheap to buy online
  • 2 plug sockets and Terminal Block -Wickes £4.50

Update: For those less confident around electrics (or who just don’t want the faff) the ready made controllers from Inkbird are getting good reviews. There are two models; the standard Inkbird termperature controller for around £35, or a wifi enabled verison for around £35.

Putting the control box together

All the bits ready to go, and a beer of course

Brew Fridge Build

Holes cut into the top and sides of the project box using a multi-tool. I then stuck the sockets on with super glue.

STC-1000 and Sockets

The inside of the box

Fermentation Fridge

STC 1000 Wiring Diagram (your hot and cold may be the other way around, make sure you label the socket correctly)

STC-1000 Wiring Diagram

All wired up and ready to assemble the box

Temperature Control

Testing it to make sure it works, amazingly it did!

Testing the Control

Heater and fridge plugged in, set to 20C and an FV full of my Sierra Nevada Pale Ale clone ready for fermentation.

The Brew Fridge in Action

Making a Brew Fridge

This really was a lot simpler than I thought it was going to be, there’s lots of wiring diagrams available to help with that side of things but once you get the logic it’s pretty straightforward.

The fridge has more uses than just fermentation, at some point I may try a lager which ferments at a cooler temperature and then needs to stored (or lagered) at a cold temperature for a period of time, I can now do this as the fridge works down to about 1C. I’ll also be able to crash cool my FV at the end of fermentation to help clear my beer ready for bottling, this is something I’ve only been able to do in winter.

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