Basic HERMS questions: location of temperature probe, whirlpooling mash tun, etc.

[MatthewMoisen]

I would like to build a HERMS system with a RaspberryPi, Powerswitch Tail 2, DS18B20 temperature probe, and a Bucket heater.

Do I put the probe in the mash tun or in the HLT? Given that the temperature varies in the mash tun, if I were to put the probe in the mash tun would that require I slightly whirlpool the wort returning from the HLT into the mash tun to even out the temperatures, or does the fact that the wort is recirculating in the first place imply that the temperatures in the mash tun are evened out?

If I put the probe in the HLT, can I assume that this is exactly the temperature in the mash tun, or do I need to do any corrections?

Will angling the returning wort from the HTL into the mash tun to cause a small whirlpool result in a "stuck sparge"? Is this method advised or not?

How do I prevent grain from clogging the pump? Would I need to use a filter of some sort to catch the particles, or would I simply Vorlauf before connecting the mash tun to the pump?

Regards

 

[RBGilbert2]

Matthew-
When I built my HERMS system a few years ago, I based it on a system I saw on the web (powersbrewery.com). Two 10 gal. coolers. HLT uses a water heater element built into the cooler bottom controlled by a Johnson digital controller; probe in the HLT water. Mash tun has a false bottom filter that outputs to a March pump that circulates thru the homemade HERMS coil and delivers the heated wort back to the grain bed by a homemade sparge arm. Mash tun temp is controlled by another Johnson with the probe in the grain bed; pump cycles on to heat wort via the HERMS coil, shuts off at temp.

Another great place to get ideas for your brewery is Kal Walner's theelectricbrewery.com site. Great tips whether you go his route or not.

Good luck on your build. It'll be fun.

 

[LandoLincoln]

I started off my HERMS rig by placing the PID thermo probe at the valve outlet of the HLT. I found out that I needed to add 3° to the HLT temperature to keep the MLT mash temperature where I wanted it. I also have a probe on the MLT valve outlet and that's hooked up to a display that just shows the temperature of the probe and nothing else. But it seemed to me that the mash temperature was fluctuating too much for my liking and it wasn't getting to the target temperature very fast. I read on here that someone else had moved the PID probe to the exit of the HERMS coil and that controlled the temperature of the HLT and they had better results from that setup, so I tried that and I have to agree that it works better for me as well.

There will undoubtedly be small temperature differences from the wort exiting the HERMS coil and the wort exiting the MLT valve. That's just the nature of recirculation, I guess. You lose heat when it goes through your tubes and pump, and you lose heat from an un-insulated mash tun. For example, in my setup, if my mash target temp is 152, the wort coming out of my HERMS coil going in to the top of the mash tun is closer to 155 and the wort exiting the bottom of the mash tun is closer to 152. Does it really make a difference? I can't honestly say. My beers do come out a tad more fuller-bodied than I'd like, so maybe I do need to drop the temp correction from 3° to 1° and see if that helps.

For the wort returning back into the mash tun in the top, there's quite a few ways that one can reintroduce the wort without disturbing the grain bed. Some people use just a simple silicon hose that's placed on top of the grain bed. I tried that, but the whirlpooling action was giving me a pretty deep trench around the edges of the mash tun. Maybe I was recirculating too fast. I fixed my problem by taking the silicon hose and then attaching a couple of 90° street elbows (CPVC) and putting a tupperware lid with a hole in it sandwiched between them, so the wort enters the MLT onto a flat surface with a rim which prevents the grain bed from being disturbed.

You prevent grain from clogging the pump by use of a manifold or false bottom. If your manifold / false bottom is designed well it should prevent any significant amounts of grain getting through to the pump.

 

[Horseshoot]

I measure the temp at the point where the wort returns to the MLT. I have an installed analogue temp probe about mid grain, in the MLT, and it is always within 1F of the temp probe at the return. I find it pretty easy to manually fire the HLT (with HERMS coil) and keep the temp spot on (less than 0.5F difference).

 

[acidrain]

I measure temp at the HERMS exit just before entering the MT. I and have an analog thermometer mid-vessel to let me know how I'm doing.
Then, I control the HLT with a PID set to about 2 deg F higher than target temp.
HERMS coil is 40' of 3/8 ID.

 

[jlash630]

I measure temp at the HERMS exit just before entering the MT. I and have an analog thermometer mid-vessel to let me know how I'm doing.
Then, I control the HLT with a PID set to about 2 deg F higher than target temp.
HERMS coil is 40' of 3/8 ID.

Where is your HLT probe located?

 

[Bobby_M]

Where is your HLT probe located?

It was located in Seattle, circa 2015.