The Homebrew HERMS Mash Tun is simply used to steep the various grains selected for brewing beer. Grain is mixed with water and allowed to steep for a set amount of time (60 to 90 minutes). After the mashing is complete, the liquid mixed with the grain is allowed to slowly drain off through the bottom valve and is sent to the Boil Kettle. At the same time, water is pumped from the Hot Liquor Tank and introduced to the top of the grain bed. This allows the residual sugars to be rinsed from the grain and is known as fly-sparging. Although there are many sparging methods available to the home brewer, I tend to stick with this style. This is the sparging method I have always used so I haven’t really experimented with some of the other popular types such as Batch Sparging.
The Beer Brewing Mash Screen
The Homebrew Beer Brewing Mash Tun is simply a 10 gallon Gott/Rubbermaid cooler that contains a stainless steel screen to filter the grain from the extracted liquids. The screen was sourced from an online home brewing supply store and it is available in several different sizes. It has a bulkhead that connects to a chrome plated ball valve. This allows great control of the output from the tank whether it is going to the Pump or is being gravity fed to the Boil Kettle. Controlling the liquid flow is essential when it is time for the sparging procedure to occur.
The Return Manifold
A stainless steel thermowell (on left by hand) contains a probe that goes to a Ranco ETC temperature control unit. When the temperature drops below your set mash point, it turns on a Pump which moves wort through a coil submersed in the Hot Liquor Tank below. This allows the temperature of your mash to remain constant. The copper Return Manifold allows the returning liquid to be reintroduced to the tank with a minimal amount of grain bed disturbance. Attached to the Return Manifold (on lower right) is a float switch that is used to turn the Pump on and off for the sparge operation. Although this could be accomplished manually, it is amazing the precise control you can have by utilizing a float-switch to control the liquid flow during the sparging procedure.
The Ranco ETC
There are two of these electronic temperature controllers (ETC) in this system. This particular one turns the Pump on when the temperature in the beer brewing Mash Tun falls below your set mash temperature. It seems to maintain the temperature of the Mash Tank to within one degree. The second Ranco ETC is located on the other side of the Stand and is used to maintain the temperature of the Hot Liquor Tank. It monitors temperature through a thermowell and turns on an hot water heater element when the temperature of the tank drops below your chosen temperature. The instruction manual for the Ranco ETC is available in PDF format here.
The Homebrew Mash Tun Wiring Diagram
I have attempted to draw a simple diagram that illustrates how I wired the components of the electrical portion of the Mash Tank. I assume no responsibility if you attempt to use this information on your system. This is just a guide. Make sure everything terminates in a GFI outlet and make sure everything is grounded to keep it safe. For most of the wiring, I bought extension cords and cut them to the necessary lengths. Use the excess wire to create any necessary jumpers. The light bulb in the diagram is a radio shack 120 volt mini-bulb and turns on anytime the Pump turns on. The advantage of this wiring is that the switch overrides the Ranco ETC so you can shut the Pump off at any time. Also, one of the outlets turns on and off based upon the ETC while the other turns on and off based upon the ETC and the float switch. The relay is an Omron G2R-1A-T 120 VAC, but I am sure you can find something similar at just about any electronics shop. If the wiring diagram is too complicated for you, here is a photograph with the wires labeled: Wiring Photo.