Building a HERMS system

Herms coil outputThere have been several posts over the past few months about mash tuns and controlling your mash temperature using a HERMS or RIMS set-up.  Controlling your mash temperature via a recirculating system can greatly help with consistency, especially when it comes to hitting and holding your mash temperature.

I have decided to take my own advice and take my personal brewing to the next level, making beers more easily replicable while simultaneously making my brew day a little less stressful by upgrading to a HERMS brewery!

The first step was to convert my 3-tier gravity system to a 2-tier system utilizing a single March pump and a plate chiller.  These two upgrades would allow me to move wort faster and not have to reach to the top of the 3rd tier to fill my HLT with water, which was sketchy at best.  It also would allow for quicker and more precise cooling instead of using an immersion chiller in a 10-gallon batch.

Next, I wanted to use my old immersion chiller as a HERMS coil.  To do this, I fitted the coil with compression fittings on both ends and attached it to the kettle via some lock nuts from bargain fittings.  This would hold the coil in place in the kettle and keep it from leaking.

herms coil in a keggle

To one end of the coil, I simply attached a coupling and a quick disconnect.  This is where the water or wort would enter the coil.  On the output end of the coil, however, I had to be a little more creative.  I had to build a contraption that would allow the wort to flow through while giving me a place to mount a temperature probe so that I could monitor the temperature of the wort or water circulating through the coil.

To do this, I soldered together a 90-degree elbow onto a copper pipe to which I attached an outlet for a quick disconnect as well as a threaded outlet for a temperature probe.  This would attach to the compression fitting at the end of my HERMS coil.

herms temp probe diagram outside of HLT with herms coil

To control the temperature, I am utilizing a PID temperature controller.  This will allow me to set a specific temperature and the PID will turn the heat element on and off to ensure that the exact temperature is held.  The PID will be mounted into a control panel box which will also house the on/off switch for the March pump and the heat element.

Below is a schematic of how everything will be wired up within the control panel.  Luckily, I have a friend that is an electrical engineer who was willing to help me out with all of the electrical work.

HERMS control panel wiring diagram

You’ll notice the large open space in the top left corner of the control panel.  This space is where I will eventually install a timer for the system.  The timer will allow me to set a specific time for the system to turn on (say 8am) and it will kick everything into gear so that when I am ready to brew (9am), all I have to do is walk outside and mash in using the pre-heated water.

control panel front

NOTE: You will want to install timers at your own risk because they could malfunction, causing the system to turn on in the middle of the night.  This would be fine (other than a waste of electricity), unless your PID were to also malfunction, resulting in boiling water all night.  If the water were to boil off, the heat element could dry-fire causing a spark.  Obviously, this is potentially dangerous, but given the many checkpoints (timer, PID, breaker), I feel comfortable going this route, despite the inherent risk.  I would still encourage anyone not to ever use one of these systems to start heating while they are not at home, as it is a potential fire safety hazard.

To mount the control panel and the necessary spa panel, I built a removable shelf on the workbench brew stand.  This will allow me to take the control and spa panels on and off easily and store them inside out of the weather, and only attach the shelf with the panels whenever I am ready to brew.  Just one more of those little conveniences I wanted to build into the system.  If your brewing set-up is in your garage and out of the elements, this would probably not be necessary.

control panel shelf front

I have not yet wired everything up, as I am still waiting on the temperature probe to arrive from China.  But I will certainly post an update on how the first brew day goes once everything gets wired up and tested.  I expect that it will help with consistency and stress.  Remember though, a recirculating system such as a RIMS or a HERMS is not going to make your beer any better.  If you’re making crappy beer, a recirculating system will not make it any better, only more consistent.  Master the basics first, and then when you have some recipes that you want to be the exact same every time, then think about upgrading to a system like this.  It’s more important to master the fundamentals of brewing than it is to spend money buying or building an advanced piece of equipment.

But most importantly, have fun!

If anyone else is using a recirculating system, I’d love to hear how it is going and see some pics!  What works well, what is easier or more difficult?  How has it affected your brew day?


Andrew Bailey

How long have you been brewing electric? Did you have to make any modifications/additions to your home wiring to get 220V to your brewing area?


Hi Andrew – This is my first foray into electric brewing. As for modifications/additions to the home wiring, I have done none. I am unplugging my dryer and plugging in the power cable for the HERMS there. Then running the cord across the hall and out the window to my brew system where it hits a spa (GFCI) box before running into the control panel . The 3-prong cord is expensive (about $1.50/foot), but it allows me to run one 5500w electric element at a time. I can’t tun on both the HLT and (eventually) the boil kettle simultaneously – that is what the 3-way toggle switch is for: , but 5500w of heat should heat that sucker up pretty fast!


Has anyone ever used their HLT/HEX for a wort chiller? I figure after the boil you could Pack the HLT with ice and cold water to cool the post boil sort.


Hi John – that can absolutely be done. I don’t do it personally, but a friend of mine who also has a HERMS brewery does it with a lot of success. He runs his wort through a plate chiller, and then through the HERMS coil in the HLT and can push it at close to full speed and have his wort in the 60s pretty easily.


Hey there,
stumbled upon your site and specifically this post. I live in raleigh. Curious to see if youd ever be interested in exchanging some emails. I have some questions regarding incorportaing a herms system into my HLT keggle. Thanks in advance!

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