Johnson Temperature Controller


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  • Johnson Temperature Controller


Most ales can be fermented at room temperature, which is usually about 70-75 degrees F. But did you know that most breweries ferment their ales at no higher than 65 degrees F and some at 55-60 degrees F? Why? Because you get a smoother, cleaner tasting beer at lower temperatures. And lagers need to start out fermentation at 60 degrees F or so, but need to be slowly brought down to just above the freezing point. And if you would like to serve your kegged (or bottled) beer at "cellar" temperatures (50-55 degrees F), your standard refrigerator won't usually maintain a temperature this high.

How do we solve these temperature control problems at home? The best way is to use a separate refrigerator or freezer with an external temperature controller. This is a device that overides the internal thermostat in the refrigerator or freezer and allows us to set the temperature more precisely and in the range we need.

To understand how the external temperature controller works, you need to understand how a refrigerator or freezer works. Basically there is a compressor that pumps cold refrigerant through some cooling coils. These coils then cool the air inside the refrigerator or freezer. Most people are not aware that a standard home refrigerator has only one set of coils and these are located in the freezer compartment. A fan blows some of the cold air from the freezer into the refrigerator portion to keep that section cool but not frozen. A freezer, of course, just has one set of coils to cool the enitre unit. Inside the refrigerator or freezer is a thermostat. When the temperature inside the compartment is above the setting on the thermostat, a switch is closed which applies AC power to the compressor, causing the air inside to cool down. When the temperature gets to the thermostat's setting, the switch is opened shutting off the compressor. Since no more cooling is taking place, eventually the temperature inside will rise again causing the switch to be closed, turning on the compressor and so on.

An external temperature controller works in the identical fashion, in fact it is a thermostat. It has a plug which plugs into a wall socket, a socket where you plug in your refrigerator or freezer and a temperature sensor that goes inside the refrigerator or freezer. You turn the refrigerator or freezer's internal thermostat to its coldest setting (so it's basically always on), set the temperature that you really want using the dial on the external controller and it takes over, turning the power to the refrigerator on and off just like the internal thermostat would do. If you're concerned that this will be hard on your refrigerator or freezer, don't be. It is doing exactly the same thing as the internal thermostat would do - in fact it will run less. is an industrial grade thermostat made specifically for this kind of application. It is housed in a rugged metal enclosure which you would normally attach to the wall next to your refrigerator or freezer with some screws. Alternatively you can velcro or double-stick tape it to the side of the refrigerator. It has an 8 foot capillary tube with the temperature sensing bulb at the end. This is easily bent around the door frame. When the door is closed the door gasket will make a fine seal around the tube without needing to cut the gasket. It has an 8 foot cord which has a special plug/socket assembly on the end. The plug side goes in a wall socket, and the refrigerator or freezer plugs into the cord's socket. Set the dial to the desired temperature and the HopTech Temperature controller will turn on the refrigerator or freezer, cool down to the setting and shut off. When the temperature rises to 3 degrees F above the setting, the unit will turn back on again. This 3o "differential" keeps the compressor from constantly shutting on and off. The temperature is adjustable from 20 degrees F to 80 degrees F - a much wider range than you'll ever need. It can handle up to a 12 amp load. It comes with a temperature adjusting knob. The overall temperature accuracy is within 2 degrees F.

Comes with instructions.