The moment you consider adding some type of temperature control to your mashing process you are usually confronted with two options: to use a HERMS or a RIMS system.

Recirculating Infusion Mash System, or RIMS for short, is a process in which the mash is continually recirculated and reheated to obtain a consistent temperature profile during the mash. Many of these systems employ an electric heating element, a stainless steel or copper pipe, a temperature sensor, a temperature controller, and a pump to recirculate the mash. A consistent mash temperature can be obtained by recirculating the mash through the tube and allowing the temperature controller to heat it whenever it starts to cool.

The second popular type of temperature control for controlling the temperature of a mash is called a Heat Exchanged Recirculating Mash System, or HERMS for short. Essentially you have a coil, usually copper or stainless steel, immersed in a tank of temperature controlled hot water. The mash is recirculated through the coil during the mash, which causes (assuming the mash temperature is lower than the tank temperature) the mash temperature to rise and the tank temperature to fall. The temperature controller controls the temperature of the mash by occasionally heating the tank of water (which is often your hot liquor tank), and also the coil, to the desired mash temperature.

Both systems work and are both heavily used, but I decided to use a HERMs system for the following reasons:

  • Heating of the mash temperature is more gradual, thereby reducing any risk of scorching the wort
  • No need to mount an external RIMs tube to anything when using HERMS
  • Because Kal did too and his system is awesome
Sourcing A HERMs Coil

Sourcing A HERMs Coil

I had considering making my own coil at one point, but thankfully stumbled upon some comments in a home brew forum discussing an exceptionally priced vendor who provides custom stainless steel HERMS coils.

All the reviews I’ve read are positive, so I ended up ordering a 50′ coil of 1/2″ ID stainless tubing with two 90 degree bends, all for less than $100. I would have a hard time finding stainless steel tubing in my home town for that price, let alone trying to bend it, so really it’s an amazing deal.

The HERMS coil will be installed into the HLT using two 1/2″ weldless bulkheads and a set of stainless steel 1/2″ compression fittings.