Budget Herms System - Part One

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Mash recirculation is a popular technique. Most of the new integrated single-vessel packages (Grainfather, etc.) include the feature. A growing number of home brewers today incorporate mash recirculation in their BIAB or multiple vessel rigs, frequently adding temperature control through either a RIMS (Recirculating Infusion Mash System) or a HERMS (Heat Exchange Recirculating Mash System). The advantages of recirculating the mash are frequently discussed. One obvious result is a very clear wort. However, the importance of wort clarity is generally considered minimal. The aspect of recirculation that is most attractive is that it can provide a consistent mash temperature, with little temperature variation from region to region within the mash. This should lead to consistent enzyme activity throughout the mash and consistent wort characteristics from brew to brew.

Control Panel
A RIMS setup directly heats the mash as it is pumped through a chamber containing a heating element and then back into the mash tun, or by direct fire of the mash tun during recirculation. The RIMS approach appears to be the more popular choice these days. One advantage of this scheme is that it has fast response and can raise the mash temperature relatively quickly. This is useful when doing step mashes or heating for mashout. The downside is the danger of scorching the mash, though with modern control systems this is probably rare.

Controller And Other Hardware Connectors
A HERMS setup recirculates the mash through a heat exchanger coil suspended in a vessel containing heated water, usually the hot liquor tank (HLT). The temperature of the water in the HLT is thus transferred to the mash indirectly through the coil. A HERMS rig can be either gas or electric. Many HERMS setups rely on direct fire heating, whether fueled by propane or natural gas. The downside is that there is a lot of volume in the heat exchanger chamber or HLT, so a large volume of water must be heated to raise the temperature of the mash; this takes time. A few degrees per minute is considered a pretty good response. Once you reach your desired temperature, of course, maintaining a steady mash temperature is easy with either system. Because of the slow response time, a HERMS can be operated either automatically via a temperature-controlled burner, as in the setup being described here, or manually by watching the temperature and adjusting the relevant burners regulator or needle valve.
Because I am, for now, committed to gas, a HERMS rig is an easy setup for me to implement. I decided to do some tests to see how such a process would work for me. I first rigged a manual system, to verify that I wanted to add HERMS to my home brewery. It worked well, so I decided to move on to automation.

Coil in HLT
My first test fixture used an old 25 foot, 3/8 inch copper wort chiller that was in the spares pile. I suspended it within my hot liquor tank and pumped the mash through it and back into the mash tun. It worked well enough to intrigue me, but the limited surface area caused a slower response than I wanted. I then purchased a 1/2 inch X 50 foot stainless steel coil from Stainlessbrewing.com and suspended it within my hot liquor tank (a converted commercial 1/2 bbl keg). The price was good, shipping was fast, and the quality pleased me. Now I had something that worked. I could manually crank up the HLT temperature and the mash temp followed right along.

Inkbird Digital Temperature Controller And Burner
Next, I temporarily rigged one of my low pressure Hurricane burners under the hot liquor tank and hooked up a Honeywell valve to be controlled by an extra Inkbird ITC-308 I had on hand. With the sensor inserted into the output of the recirculating mash coming out of the heat exchanger, I could set the desired mash temperature and the HLT burner would follow. I was getting about two degrees per minute rise with the burner mounted well below the position I intended for my permanent setup. I expect performance to increase in the final revision because the burner will be mounted closer to the kettle. All systems are go - time to start putting together a real control panel and begin transferring everything over to a new single tier brewstand. With the pumps installed, I won't need the gravity fed system I've been using.
The cooler mash tun will be no more, I will replace it with a 15 gallon SS kettle with a Jaybird false bottom. This will permit the brewing of higher gravity beers in ten gallon recipes, and will also permit directly heating the strike water in the mash tun. I will have three low pressure propane (for now) or natural gas burners (the next phase of the project), with PID control of the MLT and HLT burners and a simple on/off switch for the boil kettle burner. The stand will be a single tier, with one pump for recirculation and sparging, and another for transferring wort to the boil kettle and from the boil kettle into the counter flow wort chiller (unless I finally give in and try my plate chiller instead).
The control panel will be the topic of Part two, which will include a schematic and parts list for the panel. Part three will describe the mounting and plumbing of the burners, solenoid valves, gas manifold, pumps, and RTD sensors. Part numbers of the exotic bits will be included.
For those of you who patiently worked their way to the end of this segment, I thank you and look forward to seeing you again with Part two.
I have a HERMS system and love it. The one thing I would change from your above plan is that you mention brewing 10 gallons of a high gravity wort in a 15 gallon kettle. I would urge you to go to a 20 gallon kettle for this as I believe the cost increase to be minimal over 15 gallons and the "extra" space very welcoming. I look forward to future parts of your build.
@Roadie I agree. I purchased a ~16g kettle for 10 gallon batches and it get just enough room so not make a huge mess, but I have to watch it very carefully. If I ever switch to HERMS or RIMS, I will buy a 20G kettle so I can relax a bit on brew day. I use a 10G cooler MT for 10G batches and even that is tight.
Thank you for detailing it out like this. I'm using a rinkydink 1 vessel BIAB set up right now, and I'd like to build either a RIMS or HERMS setup by this time next year. Slow and steady will help the budget I think, plus it will give me enough time to read and research everything involved.
The 10G cooler MT I've been using is tight for some 10 gallon recipes. That's why I'm switching to a 15G kettle. The 15G boil kettle works fine for ten gallon batches (13G preboil) but it's best when I remember the Fermcap-S! Some day I may switch the boil kettle over to the HLT spot (eliminating the last keggle) and go to a 20 gallon kettle so I can do an occasional 15 gallon batch. That will be a project because the existing HLT has lots of hardware in it that would have to be transferred. Not impossible, but too much to begin while the main project is under way.
I love my HERMS system (Mash in a cooler and recirculate like above through my HLT). The one part I'll say is a little over-rated is the automation. Once my HLT is at temp - about 3 degrees higher than my desired mash temp - I just keep the burner on ever so little throughout the mash cycle and everything stays +/- 0.5 degrees.
Hopefully you will include where the actual cost came in v. budget.
@203PH I'll include prices for everything that was purchased new (which includes everything in the control panel, two of the kettles, the stand, fittings, and the HEX coil). The HLT, burners, and solenoid valves were bought used, but I'll include current new prices for those items. The only budget buster was the welded stainless steel brewstand; one could save $500 or more by fabricating one or by going to http://www.strutchannelfittings.com .
You mentioned a Honeywell valve in the article. Would you provide more details about the valve you used, please?
It's a 24VAC valve primarily used in standing pilot home furnace systems. I think the particular ones I have are VR8200A2132/U. Any 24VAC standing pilot 8200 or 8300 series with 1/2" fittings should work fine. Intermittent pilot units would be even better but would add at least $100 to the cost of each burner. I decided I could live with standing (continuously lit) pilots. You could rig any solenoid valves, but the Honeywells include safety provisions (no pilot flame means no gas to the burner) that I consider essential.
-NOTE- The use of these Honeywell valves means that low pressure gas must be used. The valves are primarily intended for use in natural gas systems (pressure maybe 5.5 inches wc). They come with the parts to convert to low pressure propane (11" wc). Most burners can be converted to LP propane by swapping the orifice and regulator. For Banjo burners, the LP orifice costs about $7.
I plan to go into more detail on all of these issues in Part 3.
@Mashinations I agree that with a cooler mash tun temperature regulation isn't much of an issue. Even with heat loss from recirculation the temperature is fairly stable. I wanted to move to a larger mash tun to permit larger grain bills so I'll be using a 15G kettle instead. The kettle also permits direct heat so I can heat strike water in the MLT while simultaneously heating the HLT. The new kettle will have greater heat loss so the HERMS will be more useful.
@Roadie I totally agree that a 20 gallon kettle would be awesome. I have a 15 gallon system and those 10 gallon batches get really close to the top.
Thanks for the kind words! Work has been crazy but I should complete Part 2 very soon. Everything is here for Part 3 and there is much less to do, so that segment should follow fairly quickly.
This is awesome I am in the stage of building a similar system. I have been stuck on how to implement the control panel for a while and cant wait to see how you plane on doing it.
I bought some chinese pid controllers a while back (mypin ta4) and the temperature would overshoot badly and keep going, never reaching a steady state or going back down to the set temperature. I ran the autotune and tried some settings of my own but they were just bad. Not sure if the inkbird ones are a step up or not. I ended up replacing them with some pid controllers from auberins that started at 40$ and were lightyears better than anything on amazon.