First, I strongly suggest that if you haven’t read Part One of this series, it might be a good idea to do so. In that segment, I discussed my reasons for using the approach described here. This portion is more of a hands-on, procedural description of how to achieve that which has already been decided upon.
Second, please be aware that I would be amazed if anyone were to follow through with an identical build. I included everything but the kitchen sink in my version because that was what I wanted to build. Three controlled burners and four PID (proportional–integral–derivative) control modules is certainly overkill for the job at hand, which is homebrewing beer. I believe that most homebrewers will find one controlled burner and one PID sufficient to construct a very effective HERMS (Heat Exchanger Recirculating Mash System). One additional burner, and one more PID would provide the option of using RIMS when desired. For this reason, I would expect that you will initially decide how much automation you want and select only those components of the system described here that fill your needs. Stripping out excess components will only make the controller even easier and less expensive to construct.
Third, I want to comment that this section describes what I intended as the core of an economical HERMS build. The control panel is intended to be a template for a universal gas-fired HERMS platform of whatever complexity is desired. The brewstand, vessels, and plumbing can be whatever works for you. This control panel and the suggested solenoid valves and burners will manage pretty much any hardware you choose.
Part Three describes the system I originally wanted to build. I invested more than I initially intended on kettles, brewstand, and hardware (QD connectors, etc.) I will describe the choices I made at that stage and how I implemented them - but folks should realize that more economical choices can be made in those areas without compromising the intent or functionality of the control scheme. For example, preliminary tests using a cooler mash tun were very satisfactory. I switched to a stainless steel pot not to improve HERMS operation, but to add RIMS capability. You may or may not have any interest in that option. Those tests were run on a gravity feed brewstand; the only pump required was the mash recirculation pump.
I added an additional pump so I could move to a single tier but that isn’t an essential part of this project. In other words, this control scheme is an economical component of a HERMS brewing system; The mechanical portion of the project can be as expensive as you want it to be, or can also be built with economy in mind.
I will provide a list of all components with sources and prices. I won’t provide a total cost because, as I describe above, I anticipate each person will select the components necessary to complete their own version of this design; they can then multiply the cost I show by the number of each component required to arrive at their final cost.
As you can see, the layout changed from my initial scheme. I switched from an STC temperature controller to a PID for the chiller output display module. That is even more of a waste of functionality than the STC controller, as that unit won’t be used to control anything, but I like it. At first, I just wanted a nice, bright digital display. In the end, I decided that a PID matching the others would look nicer and the cost was only a few dollars more. It also permitted me to use another waterproof RTD (resistance temperature detector) sensor rather than the small, unmounted sensor supplied with the STC unit. Other changes involved changing from rotary pump switches to illuminated rocker switches. This was done because they are much less expensive and use less panel real estate. This permitted adding a third pump switch to operate a recirculation pump on the HLT to maintain consistent HLT temperatures. I also added a mushroom “stop” switch in case of a hose or gas line failure.
Step One: Layout
The first step is to lay out the control panel for the components selected. The panel I chose turned out to be about right for the devices I installed. Those using fewer devices could pick a smaller box. I covered the control panel with masking tape and drew all of the holes on the tape. I then cut out the rectangular holes and drilled the round ones. Then I did the same process on the input/output (bottom) panel, laying it out for all of the connectors I would use. That got more crowded than the control panel due to its smaller size, but there was still room to add labels.
Step Two: Mounting
Next, mount all of the components and connectors on both panels. Be aware that the AC sockets I used for the pump power aren’t really intended for a thick plastic panel. I had to cut back the locking tabs so they would go inside. For this reason, I would suggest using normal duplex AC outlets if you have room (I didn’t have room in this case). The rocker switches had the same issue, but they won’t be subjected to the stresses of the power sockets so I wasn’t concerned about them.
Step Three: Wiring
First, you’ll need to acquire the correct wires, and select methods to organize them. I strongly recommend gathering an assortment of different color stranded hookup wire in two sizes. I used 18ga for the 120VAC wiring. That is plenty large enough to operate the pumps (the largest energy users), plus the PIDs and the 24VAC transformer. This isn’t an extension cord or long wire run, it is just a foot of wire inside a cabinet. In such applications, 18ga wire is commonly used for 10 Amps. I used 22ga wire for the 24V circuits. You can choose larger gauges of wire if you like, but that would only increase the cost and make wiring more difficult. As you run each wire, dress it in the path in which you intend to bundle it with others and cut each to length. At the end, you will be using cable ties on each bundle to keep things neat.
I began with the 120VAC wiring. There are only four ground connections (power input socket and pump AC receptacles) and I made sure they were all near each other. A quick daisy chain and it was handled. Then the same for the neutrals, except that the neutral also had to be extended to the rocker switch indicator lights, the 24V transformer primary, and the PIDs. The hot lead was routed through a fuse holder, the stop switch, and the power switch.The switched output was run to the other transformer primary lead, the PIDs, and the pump switches. A run from each pump switch to the corresponding pump socket completed the 120V circuits.
Next I connected the RTD sensors. The sensors I used came from Auber Instruments, and each included a socket for the panel with pigtail leads for the internal wiring, making the connections easier. Each RTD pigtail was connected to the corresponding PID. Each lead has two red leads and one white. The red leads go to pins 7 and 10 on the PID (doesn’t matter which goes where) and the white lead is jumpered to both 8 and 9.
Step Four: Testing
At this point you can power up the PID for the first round of tests. If you connect the RTD sensors, you can verify that the PIDs are correctly configured for them (select Pt if you are using PT100 sensors as I am) and that the wiring is correct by observing that all correctly indicate room temperature. The power and pump switch lights should work and you can plug in a pump (or a desk lamp) to verify that the outputs are correct.
Nearly done! Now for the 24V circuits. Choose an output lead to be the switched side and call the other lead the return. Connect the return line to the 24V indicator lights (doesn’t matter which side) and to all of the solenoid output jacks. Connect the switched lead to the 24V fuse holder, and then to a relay lead on each PID. This is where it gets tricky. The schematic shows how I implemented the 24V control leads but you may have a simpler system.You could run the other other PID relay lead directly to a solenoid output jack and you would have PID control of the burner. I recommend including a switch in the line to disable the output when not wanted. You can see how I did that for the HLT and MLT burners in the accompanying schematic. You may want to be able to switch the burner on without the PID commanding it. You would do that by running the 24V hot lead directly to a switch and thence to the solenoid output. Again, the schematic shows how I did that on the boil and MLT burners. You might want to switch a burner between two alternate PIDs, as I did, to enable HLT temperature control when the recirculation isn’t active.
HERMS Control Panel Parts List
- MYPIN® Universal Programmable Digital Adjustor PID F/C Thermostat Temperature Controller Control TA4-RNR, Powered by 90-265V AC/DC, Range: -1999 to 9999, Accuracy: 0.2% （CE APPROVED) - 4 at $23.99 ea
- uxcell® 22mm NC Red Mushroom Emergency Stop Push Button Switch 600V - 10 Pack - 1 at $6.48
- US 3 Pins Power Socket Plug Black AC 125V 15A - 10 Pack - 1 pack at $5.60 (USED THREE)
- 2.1mm x 5.5mm Male CCTV Power Plug Adapter - 10 Pack - 1 pack at $5.47 (USED THREE)
- 5.5mmx2.1mm DC Power Jack Socket Female Panel Mount Connector - 5 Pack - 1 pack at $5.59 (USED THREE)
- Ac 125v 15a 6 X 30mm Panel Mount Fuse Holder - 5 Pack - 1 pack at $5.75 (USED TWO)
- 3P IEC 320 C14 Male Plug Panel Power Inlet Sockets Connectors - 5 Pack - 1 pack at $6.05 (USED ONE)
- 2 Magentoo(TM) AC DC 24V 7mm Red Bulb Power Signal Indicator Pilot Light - 2 Pack - 2 packs at $5.62 ea (USED THREE)
- Panel Mount Red Light SPST Rocker Switch 15A 250VAC 20A 125VAC - 5 Pack - 1 pack at $6.25 (USED THREE)
- BUD Industries NBF-32018 Plastic ABS NEMA Economy Box with Solid Door, 11-51/64" Length x 7-55/64" Width x 6-9/32" Height, Light Gray Finish - 1 AT $21.25
- 22mm Latching 2 NO Three 3-Position Rotary Selector Select Switch ZB2-BE101C - 4 at $5.96 ea
- Honeywell AT140A1000 40Va, 120V Transformer - 60 Hz. - 1 at $16.28