Controlling fermentation temperature with a brewing fridge

In the UK, while most people's houses are usually kept at around 20-21°C, temperatures do vary. In the summer it can be hard to keep the temperature down and in winter, even with central heating, the temperature will often drop too low. In addition, not everyone has the space or desire to brew indoors and may be looking to brew in an uninsulated garage, shed or outbuilding.

Temperature control is important in brewing. Too cold and the fermentation can take extended periods of time, or even stop altogether. Too hot and the yeast become stressed, producing phenols and esters which will add undesirable flavours to your beer, wine or cider. If the temperature is allowed to rise too high, then the yeast may even die.

One of the best ways to control your brewing temperature is to build a brewing fridge. Normally a fridge will be too cold for brewing, but with the addition of a digital temperature controller, we can easily set the temperature to a specific point, which will usually only fluctuate by ½ to 1°C!

Using a brewing fridge, not only can you brew beers, wines & cider at exactly 20°C, if you choose to, you can set the temperature to say 13°C for lagers. You can also use a technique called crash cooling, which is lowering the temperature over 2-3 days to around 3-4°C (or lower if the fridge is capable), which will help to clear your brew. This is particularly useful for beer that has had hop pellets added, as it will cause the hops to drop to the bottom of the fermenter. It is also a very effective way to clear wine and cider, prior to bottling.

What you need

Firstly, find an old fridge with removable shelves, that does not have an ice compartment and which is large enough to take a fermenting bucket. You can also use a freezer, but not a combined fridge-freezer. It doesn't usually matter if the thermostat is faulty, as the controller will be bypassing it. You can find fridges on eBay, Gumtree and Freecycle, sometimes for free, but you can still find good ones for under £20. Next you need a digital temperature controller, such as the STC-1000 (as seen at the top of the page), which you can find on eBay. For heating in the winter, a 60w tubular heater can be used.

How it works

The STC-1000 has it's own temperature probe, which is what will be used to control the fridge. You will need to remove the fridge's plug and wire it into the STC-1000, then wire the STC-1000 into the mains. A wiring diagram is shown below, but if you are in any doubt, please use a qualified electrician.

STC-1000 wiring

Wiring diagram explained

Neutral from mains to pin 1. Use a terminal block to connect the neutral to the fridge's, and heater's neutral

Live from mains to pins 2, 5 and 7.

Live out from pin 6 to heater live

Live out from pin 8 to fridge live.

Fridge and heater neutral to mains supply.

The STC-1000 does not have an earth connection

Connect the temperature probe to pins 3 & 4

Heating and cooling 

Using the STC-1000, you can heat the fridge up, as well as cooling it down, which you may need in the winter. We use a 60w tubular heater, as used in greenhouses, which can be mounted inside the fridge. We have run the power cable through the fridge's drain hole at the rear, then connected it to the STC-1000. In this way, the controller can either turn on the fridge, or the heater, to keep your brew at exactly the right temperature.

Setting the temperature

Place the temperature probe half way up your fermenting vessel, cover it in a couple of layers of bubble wrap to insulate it and fasten it in place with gaffer tape. The temperature probe will now measure the temperature of your brew, and not the air temperature inside the fridge. Refer to the controller's instructions for operation, but normally, to set the temperature press and hold the S button until the display reads F1. Press the S button again and the temperature setting will be displayed. Now use the up and down arrows to set the temperature required. Once you the correct figure is displayed, press the power button to store the setting. You can change the temperature at any time, by repeating this operation.

Build a booze fridge, too

Got room for a second fridge? Why not make your very own beer or wine fridge? Simply connect up a fridge to an STC-1000 and set the required temperature. 

It's easy enough to change the temperature up or down, so if you know you will be drinking one particular style, you can easily set the appropriate temperature, then change it back to something else, when needed.