Justin teased it a bit in his photos from last week, but I wanted to bring all our avid readers up to speed on our Thermal Interchange Manifold project.

We were able to put TIM back into action during our last brew and everything seemed to work pretty flawlessly this go around. We were able to hold our mash at the exact temperature we were shooting for the full 60 minutes, with never more than a degree or two of variance between the grain bed and the inflowing wort. Maybe it was the thermowell…maybe it was the Desitin. Regardless, our temperatures were steady as a rock.

Take a look at those temp readings! TIM’s readings are on the top left and the grain bed temp is shown on the controller to the right. Can’t get much closer than that!

tim in action

So how does all this fanciness work?

Elves. Tiny elves chock-full of tiny elven magic. We supply them with beer and Zagnuts and they do the rest.


Sadly, Zagnuts are kind of hard to come by these days, so when Plan A fails and the elves hit the road, we are forced to turn to our backup plan…our HERMS system, which looks something like this:



Here’s how it works. Hot water and grist are added to the MLT in a predetermined ratio…typically 1.5 quarts of water per pound of grain. We stir it all together, then seal the beast up. We then start a timer, and let it sit undisturbed for 30 minutes. Prior to our dough in, we take the temperature readings of our crushed grain and on the mash tun. Using that information, we can extrapolate exactly how hot our water needs to be before transferring it to the MLT. If we get it right, which we probably do more often than not these days, once everything is mixed together it will be at our ideal mash temperature. With that target hit, we can sit back for a half hour and let the enzymes do their thing undisturbed.



Once we have hit the 30 minute mark, we switch our HERMS system on and let TIM do the driving for another 30 minutes or so before increasing the temperature for mash out. While we have a temperature probe near the bottom of the MLT, that is really just used for reference. It allows us to see what the temperature of the grain bed is, which is good information to know since that is where our sugars reside and where the enzymes are doing the core of their work.

Wort leaves the MLT and moves to our grant, drawn out by nothing more than gravity. The wort collects in the grant, where it is then sucked out by our pump and sent one of two directions depending on the temperature readings being sent to our HERMS control unit by the probe inside the thermowell at the center of our Thermal Interchange Manifold. If that probe says the wort is too hot, the controller will open the solenoid that just recirculates the wort. If it is too cold, it opens the solenoid that directs our circulating wort through the heat exchanger in our Hot Liquor Tank.


This is probably as good as a point as any to discuss the actual brains that make this process work – our MH1210F temperature controllers. These temperature controllers are very cheap (just $15 including shipping through Amazon) but they do a very good job….with a few modifications.



First off, no matter what the page or reviews might say…the probes that come with the MH1210F are not that waterproof. You will need a thermowell. We learned this lesson after burning out a probe within minutes of its first use. That said, the probe that comes with these controllers does read things pretty fast even when stuffed inside a thermowell. When we were calibrating our probes before our last brew, they equalized out faster than our “insta-read” thermometer could. Not terribly shabby.

Secondly, these controllers are only single stage controllers. You can use them to heat things up, or you can use them to cool things down…but it won’t automatically switch between modes. You can switch between modes with just a press of a few buttons, but with a little bit of extra wiring, you won’t even have to do that.

We leave our controller in “heat” mode and connect it to a DPDT relay to handle the rest. For those not in the know, DPDT relays are the bee’s knees when it comes to this kind of stuff. Essentially you can use them to automatically switch between two different circuits. Instead of controlling our “heat” solenoid directly, the circuit coming from the controller just flips the relay between the heating and circulation circuits. When it needs to heat, the heat circuit becomes live. When it is done heating, it automatically flips the juice over to the circulation circuit.

This eliminates any delay that many temperature control units have built into them to protect compressors and the like. The change is instantaneous. As such, when our HERMS system is running, the clicking of our solenoids is almost constant. Back and forth…back and forth…all mash long.

The only other notable drawback I can think of, one which I have no real workaround for, is that these controllers are very small and their buttons are pretty tiny and are a pain to work with…especially if you have big fat fingers like me. The biggest pain comes with calibration, but once you have that done, you really don’t have to mess with them much. Just set your target temps, and let them do their respective things.

That said, while they may look very similar, I highly advise against the STC-1000 temperature controllers. We started off with these in our control panel, and while they are two-stage controllers, their configurable options leave much to be desired. Even with the DPDT relay setup, the built in compressor delays would cause temperatures to skew more than we would like. Beyond that, they only read in Celsius, and while I am pretty handy with my unit conversions it’s just a step I would prefer to avoid if an equally affordable option is available. We will be keeping our STCs, but have earmarked them for a few fermentation related projects instead.

But back to our TIM and HERMS discussion.

Wort constantly flows past the thermowell inside the TIM unit. If it is at the right temp, it just flows in from the recirculation side. If the wort is a bit cool, it comes in from the heat exchanger. The source might change, but the flow does not stop. It’s a constant mingling of cooler and hotter wort, and the HERMS controller automatically switches between the solenoids to result in a mixture that comes out of the interchange manifold at just the perfect temp.

It then reenters the mash tun through the return manifold, and then the entire cycle repeats itself. Many times over until the mash conversion is complete.



That said, I’m thinking that it might be high time to glue all our parts together and call this a job well done.

I love it when a plan comes together.