For many years, I was getting efficiency at about 81% after backing into the numbers with Brewers Friend doing simple non-recirculated infusions at 2qt per lb with continuous fly sparge.
About a year ago, I built a electric RIMS 240 volt, 5500 watt, PID controlled system, so that I could do some step mashes and manage temps better. I like the set up, but my efficiency has gone down to 61% with continuous recirculation and the RIMS firing as needed to hold the desired temp. I am alright with poor efficiency as long as I have predictable results.
Yesterday I brewed a hefe, that I have done many times. The change was to a step mash starting with 15 min at 111°F, then 15 min at 122°F, and then 30 min at 150°F. This was all stepped with the RIMS. Before sparging, I did a mash conversion test with iodine and it showed that it was all converted. Did a normal fly sparge. Efficiency on this batch was 50% which means I will have very weak beer, OG 1.037. My single temp RIMS target was 1.042, which I have previously achieved, and my no circulation infusion would have been 1.055.
I was wondering if anyone else using a RIMS was seeing similar results. I am wondering if the heating element is killing off the enzymes during recirculation, but if that were true my starch test should have shown plenty of unconverted starches. I am confused by my declining efficiency.
Thoughts are welcome.