Heat Exchange Recirculating Mash System (HERMS) is a brewery system that uses two or three kettles to brew beer:

  1. Hot Liquor Tank (HLT)
  2. Mash Tun
  3. Boil Kettle

Water is heated in the HLT, then transferred to the Mash Tun using a pump. During the mash the wort flows from the Mash Tun into a coil sitting inside the HLT and back into the Mash Tun.

By passing through the coil that is submerged in hot water within the HLT the wort is kept at a consistent temperature.

After the mash the wort is usually transferred through a filter into a third kettle to be boiled.

The main difference between a HERMS and a Recirculating Infusion Mash System (RIMS) is that the heating element in the RIMS comes in direct contact with the wort while the heating element in the HERMS doesn’t.