I can't go with RIMS, I have a track record - if it can be scorched, it will.
That being said, I did a dry run on the mash side today with just water and no grain. I had checked everything separately, but wanted to see what data I could get in practice. My hypothesis was that I would wildly overshoot my temp and then watch it fall back into place. I figured I would have to set for a lower temp and then hone in from there. My experience was much different.
I think the key lesson of the day (which I really should have known) is that itâ€™s all about temp differential.
First, I had a propane tank that was light, so I figured this test would be a good way to kill its remnants. I started recirculating far too early, when the HLT was at 155 degrees. That's about 25 degrees lower than at which I expect to run the system and I believe it proved to slow/shunt the effect of everything else I tested. Adding another variable to the equation was stupid, but I donâ€™t think it had a non-translatable effect on the outcome of the test.
Second, I didn't expect the HLT water to drop in temp so significantly when I ran the mash tun liquid through the HERMS coil. The mash tun water temp was 63 degrees - I walked it up to 150 from there. In the first 5 minutes my HLT temp dropped 10 degrees, with a big flame under it. Note to self, when adding heat to one system, you are taking it away from another (dumbass). From there the temp steadily climbed (both in the mash tun and the HLT) and in the end I peaked out at 166 degrees in the HLT and hit my 150 in the mash tun.
Third, the massive temperature overshoot I expected never occurred. Once I hit 150 my pump shut off and I watched the temp closely. I was getting low on propane at this point and the flame was not as hot, but I still had 166 degrees of heat in the HLT. In about 8 minutes I lost heat in the mash tun and hit 149, the pump kicked on and brought it to 150 in about 3 minutes (while I watched the flame and temp die in the HLT). I have to imagine that the thermal mass of a bunch of grain would buffer any overshot of temp even further making this an extremely viable method to control mash temp. I also came to the conclusion that I need to insulate the mash tun. I currently mash in a Gott cooler and lose maybe a degree over the course of 90 minutes. If I expect to even be close to replicating my current recipes on the new system, I need to ensure I donâ€™t have that kind of fluctuation in temperature.
All in all, it was a good system test. Iâ€™m glad I did this and am very happy with the results. Iâ€™m sure HERMS is going to be a great way to go for me. Iâ€™ll post more to this thread as the build out continues. Now I have to figure out how I am going to get a single tier stand for a bargain basement price.