FAQ: HERMS vs RIMS?

 

A HERMS coil submerged in the Hot Liquor TankA HERMS coil submerged in the Hot Liquor Tank

Blichmann RIMS RocketBlichmann RIMS Rocket. A popular choice for RIMS.

 

Introduction

We get asked all the time which is better for heating the mash / wort: HERMS or RIMS?

This FAQ will provide some information as to why we choose HERMS over RIMS for our Electric Brewery design.

Both HERMS and RIMS add heat to the mash through a separate heat source while the wort is recirculated continuously. When properly designed and used, both provide a means to very accurately control mash temperature. They are both 'set it and forget it' approaches.

On a HERMS (Heat Exchanged Recirculating Mash System) setup the wort is gently heated by pumping it out of the Mash / Lauter Tun (MLT) and recirculating it through a (usually) stainless steel coil submerged in the Hot Liquor Tank (HLT) water before it is returned to the mash (see pictures below).

Hose hookup in a HERMS setupHose hookup in a HERMS setup

STEP 5: Mash

In an electric HERMS setup the heating element in the HLT heats the water and the water heats the wort passing through the coil. This is an indirect approach to heating the wort. The two liquids are never more than a degree or so apart, and the wort can never go above the temperature of the water.

A RIMS (Recirculating Infusion Mash System) setup is similar in that the wort is also pumped out of the MLT but this time it passes through a small chamber (often a pipe or a tube) that contains a heating element. The wort is directly heated by the element, often to a temperature much higher than the target point. The wort is then returned mixed in with the rest of the mash.

Because of the constant recirculation during the entire mash period (usually 60 minutes or more), both HERMS and RIMS produce an incredibly clear wort going into the boil kettle. Think of it as a continuous vorlauf (German for "recirculation"), the process of clarifying the wort being drawn out of the mash tun. This helps minimize the amount of grain particles introduced in the boil which is a good thing, as boiling them can produce unpleasant flavours (mostly from the lipid-rich embryo and the phenolic compounds in the husk).

Wort collecting in the Boil KettleWort collecting in the Boil Kettle. After a long recirculation the wort is very clear which helps reduce astringency.

 

Which is better? HERMS or RIMS?

Setups can be designed around either HERMS or RIMS. Both can and will make excellent beer when properly designed and used. Our Electric Brewery design however is based around HERMS as we find there are less risks, less caveats, less cost, less complications as compared to RIMS based designs.

 

What are the downsides to RIMS?

  • With RIMS there is a risk of scorching the wort if the pump is stopped for even a short period of time (seconds), ruining the entire batch. This makes the beer taste like an ashtray. It is not a subtle smoky flavour like in a rauchbier (a type of beer with a distinctive smoke flavour). It is not something that can be fixed. If this happens the batch has to be dumped. This situation can never present itself with HERMS given that the wort in the HERMS coil is never heated past the temperature of the HLT water. If RIMS is to be used, we'd suggest interlocking the RIMS element with the wort pump so that the element can't be on if the pump is not also on. Even better would be some sort of flow interlock as the pump head may be clogged or the pump valve closed. In other words, use a flow valve to check if wort is flowing before you allow the RIMS element to be on. This of course adds extra cost / complexity / cleaning.
  • You can't run the RIMS element at the same time as the HLT element on a standard 30 amp dryer circuit so a larger 40-50 amp circuit is required, increasing cost. RIMS is used to heat the mash while the HLT element is needed to heat the sparge water. With HERMS used in our brewing process this is not an issue as the HLT and mash are heated using the same element. The mash always follows the HLT temperature so it's only natural to use one element to heat both. We see no advantage to using separate heating elements as you will always want to increase both to eventual mashout temperatures (~168F) before starting to sparge. Controlling them separately has no benefit.
  • With RIMS the non-gentle heating of the wort may deactivate the enzymes due to overheating. With HERMS the wort is never heated past the HLT temperature since both are at mash temp. Note that this is generally considered one of the lower risks with RIMS given that alpha amylase (the primary enzyme in conversion of the malt starches to sugars) begins to break down at temperatures above about 160F and evidence shows that it takes a considerable period of time before a significant portion of the enzymes are compromised. The relatively short period of time the wort is at a high temperature is probably not a problem.
  • RIMS is more expensive, more complex, and requires more parts. RIMS requires a third element and in most cases will require more than 30 amps so a larger control panel with more parts is required. A tube or chamber of some sort to hold the RIMS element is also required. This RIMS tube needs to be safely mounted somewhere. Given that the tube must be cleaned after each use it's often held together by quick release Tri-Clamp (Tri-Clover) fittings, further increasing the cost. Some will use less expensive NPT pipe fittings but having to take a wrench to your RIMS tube to disassemble / reassemble every time you brew grows old fast. A separate HLT is still required to heat up water, including the sparge water. With a HERMS setup the HLT with integrated HERMS does double-duty. Because the mash temperature and HLT temperature are always in sync, it makes sense to combine instead of having separate vessels.
  • RIMS is more difficult to clean. The extreme localized heat and use of a hidden / embedded heating element in the RIMS tube means the element gets baked on crud, sometimes even more than what happens in the boil kettle. The boil kettle element needs to be sponged / cleaned and the one in the RIMS tube is no different. This requires that the RIMS tube be disassembled completely to clean the element after every use, unless some form of strong (caustic) cleaners made for CIP (clean in place) is used instead. With our Electric Brewery design the HERMS coil is automatically cleaned during sparging because the hot sparge water is slowly passed through the HERMS coil first (see our Brew Day Step by Step guide for complete details). No disassembly or cleaning is ever required.
  • An improperly designed RIMS tube may explode if clogged. The Blichmann RIMS Rocket (for example) has a pressurized red rubber stopper that will blow if ever a dangerous pressure situation was to present itself, allowing the boiling wort to escape. We guess boiling wort spraying all over the room is less dangerous than shards of metal! 😉 This situation can never present itself with HERMS given that the wort is never heated past the temperature of the HLT.

 

What are the benefits of RIMS?

  • RIMS may have faster heat times. Because a much smaller chamber is used to heat the wort, all things being equal a RIMS setup will heat the wort faster than a HERMS setup as there is less volume to heat. A HERMS setup may have 10-12 gallons of water to heat in the HLT while a RIMS chamber may only hold half a gallon to a gallon. When combined with the MLT volume that could mean that a RIMS setup may need to heat half as much volume as HERMS. Logic dictates that it should therefore heat about twice as fast as the less volume an element is heating, the faster the heating will occur. Unfortunately most things are not equal however between RIMS and HERMS setups: In order to avoid the risk of scorching, RIMS users will often use less powerful heating elements in their RIMS chamber. A 5500W/240V element running at 120V is a popular choice as it produces 1375W (1/4 the power). At this lower power output the risks of scorching or denaturing enzymes is greatly reduced, but of course, heating times are increased as it's only 1/4 the power output. The higher the power output on the RIMS heating element, the higher the flow rate has to be to avoid scorching. This may require faster pumps and careful attention to design. Unfortunately the faster the flow, the more chance of we have of compacting the mash grain bed too which in turn impedes the flow and we're right back to possible issues with scorching. It's a balancing act that RIMS users who want the fastest heat times have to live with.

 

Conclusion

For us, HERMS is simply a better choice with less risk, less cost, and works well with our brewing process. We see no advantage to using RIMS, only higher cost, more risks, more complexity, more cleaning.

We've been using our HERMS setup since 2009 and there hasn't been a single situation where we wished we had a RIMS setup. There's nothing we're missing, nothing we wish we could do that we can't do today, nothing that we can think of that we won't be able to do in the future. This includes complex 3-4 hour multi-step mashes (possible on either setup).

If a brewer prefers to minimize heat and ramp times in the mash and HLT, we still recommend HERMS but suggest doubling up the number of heating elements in the HLT. That will cut your heat time in half. Our 50A Electric Brewery Control Panel for 30+ gallons is perfect for this, and therefore isn't just beneficial with larger batches. Someone brewing 5-10 gallon batches could use this control panel and stick with one heating element in the boil and use two in the HLT. The benefits of quickly ramping through temperatures in a multi-step mash is questionable however as enzymes don't act instantly. We would only consider more power in the HLT for brewers looking at shortening their brew day, not because they're interested in making better beer. 

You may have different needs/requirements so make sure to review and consider everything before starting your brewery build.

Questions? Visit our FAQ: HERMS vs RIMS forum thread.

More information on HERMS is also available in our Hot Liquor Tank build article.

For complete details on our brewing process from start to end, see our Brew Day Step by Step guide.

Good luck and happy brewing!