HERMS stands for Heat Exchange Recirculating Mash System and is a specific implementation for a brew installation. The HERMS setup makes use of 3 kettles, the hot liquid tank (HLT), the mash tank (MT) and a boil tank (BT).
The Hot Liquid Tank
The HLT is used to control the temperature of the wort in the mash tank by circulating it through a metal coil that runs through the HLT. The HLT is filled with hot water and kept on temperature with the heating element on the bottom. The heating element is controlled by a BrewPi in combination with the Brewblox software. The temperature sensor that is fitted in the HLT will send its readings to the BrewPi who will then power on the heating element to reach the required temperature.
The hot water in the HLT is circulated through a water pump and a whirlpool inlet that will ensure a constant flow and heat distribution through the HLT. The wort is pumped through a separated wort pump that will circulate the wort through the metal coil in the HLT.
The hot water that is stored in the HLT is also used later in the stage when we are going to sparge the wort in the mash tank. The hot water will then be used to flush all the sugars of the brewing dregs to ensure maximum efficiency.
The Mash Tank
Next we come to the mash tank, the mash tank is used for the mash process were we extract all the sugars and flavors from the grain bill that we use in our beer. During this process we circulate the wort through a filter plate and run it through the coil to keep it on a stable temperature. After most of the sugars and flavors are extracted we will drain the wort to our boil tank and will use the hot water from the HLT to sparge the last sugars from the brewing dreg.
During the sparging process we slowly pour the hot water over the grain bill and let it filter through the filter mesh on the bottom of the tank. By using the force of gravity we let the wort drain to our boil tank.
The Boil Tank
The boil tank has a pretty simple setup with a heating element and a temperature senor. The heating element is used to bring to wort to a boil and keep it at a “rolling” boil for the duration of our recipe. To ensure that the wort doesn’t burn on the bottom we use a wort pump to circulate the wort through a whirlpool outlet that will create a vortex during the boiling process.
Depending on the recipe we will add our bittering hops during the boiling process that will add a certain bitterness to the beer. To prevent the hop particles to combine with the beer we make use of a hop spider with fine mesh that will only let through the flavors of the hop.
After we reached the end of our boiling process we will hook up our plate cooler to chill the beer down for the whirlpool. During this phases we will add the hops that are responsible of the aroma and flavors that the beer will have. We lower the temperate to between 70-80 degrees and let the hop sit in the hop spider while maintaining the vortex. Now that the beer has absorbed all of the hop flavors we will chill the beer down to fermentation temperature.
Command & Control Center
As our command and control center we make use of the BrewPi Spark 3 combined with the Brewblox software that is all running on a Raspberry Pi. The BrewPi Spark is used to receive inputs from the sensors in the tanks and output signals to the SSR (Solid State Relays) to control the power to the heating elements and pumps. To process and control this information we make use of the Brewblox solution that is an amazing project to support brewers in both the brewing as in the fermentation phase.