Originally Posted by disney7
Hey guys, I'm building a HERMS system and I have a question:
If you are using a cooler for a mash tun, why continue to circulate after you have hit your mash temp and things have had a chance to equalize? Doesn't that happen pretty quickly? Why continue to run the pump and HEX?
My current system will maintain a temp with about a degree loss in the MLT cooler over an hour... getting it to the exact temp I want has been the problem thus far and that's why I'm building the HERMS system.
Also, what flow rate do you go for? As much volume as possible without getting a stuck mash/sparge?
I actually don't start recirculating until ~10 min into the mash a lot of the time. Since I often heat my strike water in my HLT (always when doing double batches), the water in the HLT won't be at the proper temp for running the HERMS right away. IMO a HERMS is more for maintaining temps, or ramping temps up than it is for hitting your strike temp. If your main goal is hitting your strike temp accurately, building a HERMS isn't the best or easiest answer IMO.
If you take the time to input the mass and specific heat of your MLT, weight and temperature of grains, desired mash thickness and temp into any brewing program, the strike temp it gives you should get you really close to your desired mash temp. Brewtarget is totally free and does a pretty good job. After a couple batches you should be able too fine tune it to hit your mash temp dead on every time. Mashing in slightly thicker than your goal will leave room to add a little cold or boiling water to make slight adjustments. Even if you have your HLT water at the proper temp immediately after mashing in, it may take some time for the mash temp to equalize depending on how much adjustment is required. It's often much faster to mash in slightly thick and add a little hot or cold water.
As for reasons to recirculate throughout the mash, the main two were mentioned above: reduction of temperature stratification in the mash, and wort clarity. Most people keep the flow pretty slow. This helps prevent mash compaction and stuck mashes. It doesn't really need much flow to maintain uniform temps.