MT temp variations

Recently had the maiden voyage with our new system. Electric HLT with HERMS. Propane fired BK.

My question is this. We did a protein rest at 122 that went beautifully after getting the strike water temp exactly where it needed to be with the HERMS. Then the recipe called for ramping to 154 over 15 minutes. This also went fine but once the 154 temp was reached we left the HERMS running to hold the temp steady. The temp of the wort entering the MT was right around 154, but the temp in the center of the MT crept up to 160. Any thoughts why this happened?

thanks

Thinking about it more, I have a new question. Do people who use HERMS setups stir their mash periodically during the Mash? I didn't think it was necessary, but maybe that is the only way to avoid temperature stratification.

Anyone?

There is an issue with overheating your HLT. 2 questions that will help us solve it:
How many temp probes are you using to control the temp, and where are they located?
Also how does the HLT operate? is it being recirculated, or stirred? Or does the water stay still while you run the wort through the HERMS?

To your second question, you should not have to stir the mash (but you may and I usually do anyway). The temp stratification can only come from overheating the water.

Great questions, I should have thought to give this info too. The probe that controls the temp is located where the wort exits the HEX coil. It is mounted in a "T" fitting. Then a hose attaches to that fitting and brings the wort back up to the MT. The HLT is being stirred the whole time by an electric stirrer.

Also, both the HLT and the MT are converted kegs wrapped with reflectix.

Cool cool. I recommend that you control the HLT heater with the temperature of the water itself in the tank, not the wort. The configuration you have will allow the HLT temp to go higher than your target wort temp. That is fine for mid-ramp, but it will equalize given time to do so. And your HLT cannot "cool" , so see what I'm getting at?
I would set your water temp for 2 degrees above your target, using a temp probe directly in the HLT, and let it go until the target is reached in your wort. At that point reduce the HLT temp if needed so that the wort never gets above that target.

Have a brewday and watch all temps very closely and you will pinpoint what is happening.

Thanks. Sounds great. I'll give that a try next time.

Budzu said:

The temp stratification can only come from overheating the water.

Click to expand...

Exactly! In my setup, the HEX coil is in the HLT, which is stirred. To maintain a mash temp, my HLT has to be set at 3 degrees higher than I want my mash temp.

The only way your mash got to 160 was because the wort was above 160 exiting the HEX at some point, perhaps during ramping.

Yeah my 10g system also has to be set 3 degrees higher to hold the MT steady. This is only due to temp loss of the MT and the return hose itself. You can minimize that by insulating the wort return hose, and your MT, and the valves etc. that the wort travels to the MT through.