In all grain brewing, heated water is added to milled grain which allows the enzymes in the grain to break down the long chains of carbohydrates and turn them to fermentable sugars. These temperatures control the character of the beer that is being brewed by how much fermentable sugar is produced or not produced and temperature control is the key to success. One of the advantages of using a H.E.R.M.S. is the ability to not only hit these temperatures, but to also hold it there for the required amount of time to allow these conversions to take place. Just hitting the temperature is not enough for a quality product to be brewed, you have to maintain the temperature throughout the mash and that is where the H.E.R.M.S. really shines. Since pumps are used, the mash water can be circulated throughout the mash, eliminating hot or cold spots in the grain bed.

Hot water is pumped from the HLT to the Mash Tun via the main system pump. Calculations have to be made to find the correct temperature to achieve the enzyme reactions for the beer style being made. I use Pro-Mash for these calculations which consider the thermal loss of temperature of the Mash Tun, the plumbing to the tun and the grain temperature. Once these considerations are made, the mash water or Mash Liquor is recirculated to keep them at the proper temperature. Below are pictures of the Mash Tun and the plumbing that takes care of this. An added benefit to using a recirculating system such as this is that you constantly filter the mash liquor throughout the process and come out with a very clear runoff to the brew kettle.

Below is a picture of the ice cream freezer motor that was modified to drive the stirrer within the Mash Tun. More about this is on the "Mash Mixer" page.

The Mash Tun is a converted 15 1/2 gallon keg that has been wrapped with insulation to help maintain temperatures for up to 2 hours in some cases. At first I used 3 inch fiberglass insulation covered with thick gauge aluminum to take care of this. Since then, I have gone to a foam camping mat which seems to work even better at holding heat for long periods of time.

For circulation to be possible, a screen of sorts in the bottom of the tun is required to keep grain and husks from fouling the pump and to allow the wort to clear prior to boiling. Here are pictures of my screen which is made of perforated stainless steel and has a 1" stainless steel braid below it. As one of the new additions I added another internal part of the strainer using 2 stainless screens wrapped and clamped to the copper pickup manifold. The manifold with the braid and screens would do the job by itself, but since I have a mixer in my tun, I needed a way to keep it centered in the tun and a bottom for the mixer to scrape to allow thorough mixing. This is better shown in the "Mash Mixer" Page.