From IBUs and IPAs to BJCP and BIAB, it’s hard to make it through a conversation at ye olde LHBS (local homebrew store) without running up against an acronym or two.
Among the more mysterious acronyms to new all-grain brewers are RIMS and HERMS, which are two advanced systems for maintaining mash temperature, automating the brewing process, and improving consistency from one batch to another. Here’s what you need to know about them.
Recirculating Infusion Mash System (RIMS)
In a Recirculating Infusion Mash System (RIMS), wort is pumped from the base of the mash lauter tun (MLT) through a heater and returned to the same vessel near the top. Recirculating the wort in this way promotes clarity by filtering wort through the grain bed during the mash. It also helps maintain an even temperature throughout the mash and permits brewers to raise the mash temperature easily when necessary.
Heat Exchange Recirculating Mash System (HERMS)
A Heat Exchange Recirculating Mash System (HERMS) is very similar in theory to the RIMS setup described above. The difference lies in the way wort is heated after it leaves the MLT. While a RIMS system relies on direct heat, a HERMS system takes advantage of the hot water contained within the hot liquor tank (HLT) that will eventually be used for sparging. Wort passes through a coil of metal tubing, usually copper, that is within the HLT. As wort flows through the coil, heat is transferred from the hot water, through the metal tubing, and into the wort. In all other aspects, HERMS is the same as RIMS and achieves the same goals.
Advantages and Disadvantages
RIMS and HERMS are advanced homebrewing systems that many homebrewers won’t ever touch. They’re more complex than cooler-based systems and have many parts that can break and require maintenance. But brewers who have the welding and electrical skills to build one will no doubt be rewarded, while those with deep pockets can purchase a ready-made system from many suppliers. And the improvements in repeatability and control are significant.
The choice of one over the other is largely one of personal preference. HERMS uses fewer parts and less energy for most single-infusion mashes, but RIMS may come out ahead for brewers who routinely perform stepped temperature mash regimens.
Either way, once you get one of these advanced systems up and running, you’ll be the envy of your HBC (homebrew club).