HERMS Theory

HERMS stands for Heat Exchanged Recirculating Mash System.  Much has been written on the web about the technical details of the HERMS and its sibling the RIMS (Recirculated Infusion Mash System) and the pros and cons of each compared to the other.  I do not intend to repeat this as you can find it all from the links page.  What I will do is give a brief overview of what the HERMS actually does........

When brewing, the body and alcoholic strength of the finished beer are, in part, determined by the temperature at which the grist is mashed. 

The HERMS allows the brewer to recirculate the wort from the mash tun, through a heat exchanger and back into the mash tun.  The temperature of the recirculated wort is controlled by the heat exchanger which, as a result, controls the temperature of the mash very precisely.  The added benefit is that the action of recirculation clarifies the wort by using the grain bed as a filter.

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