Controlling Mash Temperature

For German multi-step mashes, temperature control plays a more prominent role that it would for infusion mashes. The temperatures are constantly monitored and increased over several intervals.

Hochkurz decoction mash with short protease rest

I have a degree in Computer Science from the University of London, so I naturally wrote software to control this process (Interface in Eclipse RCP, controller was in Arduino).  However, I noticed a few shortcomings when decoction mashing.  Back then I had a little motorised agitator, but it really began to struggle as the volumes increased.  Also, having a laptop in a brewery is messy at best.  So I looked for alternative solutions and found that PID Process Controller hardware was a very good solution.  And their PID auto-tuning worked really well — something I struggled with when dealing with the Arduino.

I’ve tried a few and the best value for money was the Omega-CN730.  This controller takes a multitude of inputs such as the widely-spread PT100 RTD, or Thermocouples.  Thermocouples are more sensitive to input and I found them the best to work with, especially when set to display at 0.1 degrees accuracy.

Again, these thermocouples could be mounted more elegantly on top of the kettles.  Right now I just stick them in and it does a fine job like that.  Later this will most likely end up mounted alongside with the agitator.

But for now,  the manual process is totally sufficient. No need to go over board (just yet!).

Another good thing is that this process controller has RS-485 communications — which allows me to engineer software to control setting the various temperatures as well as starting and stopping the device, at a later stage.

Any thermometer would do really.  Just make sure they are lab grade and calibrated.  Electronic thermometers need calibration too!  Don’t assume they will display the correct values when delivered.  They rarely do.

Currently I have two PID controllers.  One for the main mash tun, the other for the decoction tun.   This way I can ensure that the temperature in the main mash tun won’t drop too far once the decoction is being worked over (a process that takes at least 60 minutes as one can see from the graph above).  It’s far less hectic than it shounds, but beware of running the Hendi plates at full tilt!  Many of the mashes assume a temperature increase of 1°C per minute.  Don’t go too fast through the various temperature ranges.  Your enzymes will thank you for it!

My PID Process Controllers mounted on a rustic wood board.
Controlling Fermentation Temperature

Needless to say that any fermentation is best conducted in a temperature controlled environment.  My fermentation equipment consist of one tall larder fridge that I found on Gumtree, as well as one chest freezer sufficiently wide to accomodate 6 x 19l Cornie Kegs.  This is where the beer disappeares for conditioning and harvested yeast is kept.

Temperature controllers for fermentation

PID process control would be complete overkill — and unnecessarily expensive.  The very popular STC-1000 has two signal outputs.  One for heat, the other for cooling.  An inexpensive 60W tube heater provides the heat in the fridge.  The heater is intentionally underpowered so that any temperature changes occur rather mildly and avoid shocking the yeast.  Another STC-1000 controls the chest freezer and keeps it at a temperature at the optimal lager temp at -1°C to -2°C.  The 10 Ampere at it’s teminals is high enough to wire a socket directly to it so that the fridges can be switched on when cooling is required, and the heater when the temperature is too low.  Using sockets with seperate switches for the fermenter is a good idea.

For those of you not so familiar with electrics, you can work out how many watts you can connect to a socket by multiplying the current (in amperes) with the voltage.  In our case that’s

10A * 230V = 2300W

Plenty to power my fridge or my 60W heating element.  If in doubt, do have an electrician check it over.