I get a lot of hits on this blog from people searching for HERMS systems and I feel bad that although I designed this brewery to have one, I have yet to build it. If you came here looking for one all I have is the design on an old post, back from when I was planning the system.

A HERMS (Heat Exchanged Recirculating Mash System) system recirculates the wort during the mash through a heat exchange, like a copper coil, suspended in a vessel filled with water. The water can be heated to different temperatures and the recirculating wort will adjust to that temperature thereby raising the temperature of the grain bed.

The benefit to this design is that there is no direct flame on the MT so there is no scorching. The vessel can be the HLT, as it is in my design, or a separate container altogether.

These days most of the grains used in brewing are fully modified and don’t need (according to most sources) to spend time mashing at the lower temperatures in order to convert. Most homebrewers simply do a single infusion mash at their desired temperature.

So why would someone want to build a HERMS system?

There are a couple of reasons why it may make sense. One really good reason would be if the MT insulation was not holding the proper mash temperature long enough. This occurs to some in the colder months and even my well insulated MT will drop a couple of degrees when it’s really cold out. The temp of the HERMS can be adjusted to insure a proper mash temp.

Another reason is that by recirculating constantly throughout the mash, the grain bed will set up as a great filter for itself and the runoff will be very clear. This is one of the biggest reasons I plan on building one. I use a False Bottom in my MT and it takes quite a lot of time before the runoff clears of small particles. Right now I always keep a hop bag tied to the end of the hose to the kettle to catch any that get through. Not the most effective of techniques.

One more reason is the ability to repeat subsequent mashes. Even a degree or two difference will produce a different beer so the ability to regulate the mash is highly desirable.

And one more reason that I certainly hope is true is that the constant recirculation should improve my brewhouse efficiency. In other words, I should get more sugars from the same amount of grain.

Now why haven’t I built the HERMS yet? Two main reasons come to mind. #1 is that I’ve had pump issues up until very recently. One of my pumps was not working well enough and constantly needed to be stopped and started. After a very nice guy donated a pump head from a blown pump, I think that problem is fixed and we can move on to the next reason. #2 is simply money. Copper is very expensive. As are all the additional valves and parts necessary. At this point I’ve got nearly everything except the copper coil. I need at least 25 feet of soft copper tubing. Next time you are in your hardware store, take a look at the cost of copper tubing and this reason will be very evident.

But just so you don’t have to go all the way back through my old posts let me pull up the orriginal design to give you an idea of what my plan is.

I will further modify this before constructing it. Not everything on this design is accurate to the way the rig was built. The main difference is that the plumbing will be simplified (if I can get my brain around it) and both the entrance and the exit for the HERMS will most likely be near the top of the HLT.