There is a strong trend these days toward hot side temperature control, whether merely to maintain stable mash temperatures or to permit automatic temperature ramping, as for step mashes or for mashout. The majority of systems seen use modern electronics combined with electric heating elements, and provide very fine control of temperatures and in most cases the use of proportional, integral, and derivative controls to prevent temperature overshoot.
The good news for those who prefer a gas-fired system is that we have that functionality available to us as well, and it isn't terribly difficult or expensive to implement. Broadly speaking, we have three kinds of burner controls from which to choose. We can use our existing high pressure burners and add solenoid valves, igniters, and sufficient technology to safely operate them. The BCS series controllers come to mind. Their job is to command gas flow when required and fire an igniter to light the flame each time. Critically, they must also monitor the flame and if it is not ignited when it should be, they must shut off the gas supply. The Tower of Power is an example of a turnkey system offering similar functionality for low pressure systems. The third possibility is a DIY low pressure setup.
Low Pressure System for Burners
Why go with a low pressure system? For one thing, any natural gas setup will be low pressure, so a low pressure control scheme will be usable by the natural gas crowd. Once one has a low pressure propane system in place, conversion to natural gas is a very small step so a low pressure system inherently offers that option. Best of all, going with low pressure (either liquid propane or natural gas) permits the use of readily available hardware in common use in gas furnaces. This means that we can piggyback on their economy of scale rather than using components manufactured in small quantities (and with correspondingly high prices) for our hobby use.
To use a propane burner at low pressure, a low pressure orifice is required. That is the only difference between burners that are offered as “high pressure” or “low pressure”. You can convert your existing high pressure burners to low pressure with a quick and inexpensive orifice swap. I use the very common 10 inch “banjo burner” (available from many sources) with orifices from brewershardware. They, also, offer a high quality burner mount and the required low pressure regulator.
The next decision is whether to use a standing (always lit) pilot or an on-demand electrical igniter. That choice will drive the choice of solenoid valves. It is about $100 per burner
cheaper to go with standing pilot valves so that is what I did. The Honeywell VR8200/8300 series is just right for our purposes. It is available in many variants but what we want is the version with ½ inch MPT threads on the input and output. This a source offering a good price: I believe this includes necessary parts (one spring, actually) to convert to liquid propane.
Now you will need a standing pilot assembly with thermocouple. This is a suitable burner/bracket assembly
To that you will add a gas line to supply the burner and a thermocouple. This is the thermocouple I used, but you can select longer or shorter sensor lines as required by your configuration: I recommend aluminum gas line to feed the pilot. You can buy 1/4 inch aluminum gas line in 60 inch lengths, including both required connectors, for under $10 at many suppliers. Any inexpensive tubing cutter will make short work of the aluminum, and it is easier to bend without kinks than copper.
Creating A Gas Manifold
To ensure sufficient gas volume at the low pressure being used, you will want to keep everything at 1/2” feeding the burners. A simple gas manifold can be made up of black pipe (available in various lengths and already threaded at any home improvement store) and tee fittings at each required valve. Use gas pipe dope, not tape. Come to think of it, you should probably have this part of the project done by your local heating/cooling tech. A case or two of homebrew should cover the bill. If you choose to do it yourself, as I did, I am not responsible for anything that happens to you and yours.
Each gas valve is mounted directly to a tee connector via a short pipe nipple. Don't forget the dope. Mount the burners wherever and however you choose. Connect a short flexible gas line from each valve to its respective burner. Make sure each valve has the proper regulator spring installed for the fuel you are using. Mount the pilot assembly as directed in the instructions and connect the gas and thermocouple lines (make sure you installed the correct orifice; it comes with both). For propane, rig a low pressure regulator to feed the manifold; for natural gas, just connect a gas line to the manifold. CHECK FOR LEAKS!
At this point you can supply gas and light the pilots. If all goes well there, it is time to get the burners going. To do that, we will need the pilots to be lit and 24VAC applied to the solenoid valve. I used a Honeywell AT140A1000 transformer to source the 24VAC; it easily supplies all three valves at once. You will hear a significant “click” as the solenoid activates, followed (with any luck at all) by a quiet “whoosh” as the burner lights. Once lit, a low pressure burner makes almost no noise so don't rely on sound as an indicator that it is lit.
Gee whiz – that isn't very automatic! Even if you wire a switch, you still have to turn the burner on and off by hand.
Yes, I promised temperature control and here is a quick rundown on how that can be achieved. The very simplest and cheapest way is to use a $35 Inkbird ITC-308 controller just like the one you already have on your fermentation chiller. For my earliest tests of this hardware, I used an ITC-308 with the Honeywell transformer plugged into it. When the Inkbird demanded heat, the transformer activated the solenoid valve, and fire happened. The Inkbird's temperature sensor can be inserted into whatever liquid you are trying to control. With simple on/off control, temperature overshoot can be expected. It is only slightly more complicated and expensive to use one of the commonly imported PID controllers. My final setup uses the $25 MYPin TA4. Watch out – you do not want the version with an SSR interface built in. You need the relay output version (TA4-RNR rather than TA4-SNR). I used RTD sensors from Auber that actually cost more than the PIDS but they are very convenient; they thread directly into a 1/2” MPT bulkhead fitting and have cables protected by steel braid. I will address wiring and programming the PIDs in a later article. For now, just be aware that any PID circuit you see that uses an SSR to control an electric burner can be changed to solenoid control by (a) eliminating the SSR, (b) switching to a relay output PID, and (c) changing the parameters so the integration time is in minutes rather than in milliseconds.