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.

  • 3
    When is the last time you calibrated your mash thermometer? What are the odds that maybe you actually mashed at 105, 115, and 145 F? Or the other direction at 120, 130, and 160 F? Be sure to test your thermometer in both ice water and with boiling water corrected for your particular elevation above sea level -- water doesn't actually boil at 212 F except at sea level. Also.... personally I would skip the 122 F rest and would have held for at least 40-45 minutes at 150 F.
    – dmtaylor
    Oct 29, 2019 at 22:26
  • How are you calculating efficiency?
    – brewchez
    Oct 30, 2019 at 18:00
  • Has your milling changed? Also wheat malt is smaller than barley malt, so will need an adjustment for milling. Maybe this didn't happen, and your wheat was partially un-milled.
    – Kingsley
    Oct 31, 2019 at 3:57
  • I have not calibrated the PID temp controller in 6 months, so that is a good idea.
    – Icebreaker
    Oct 31, 2019 at 13:46
  • 1
    I am curious how recirculating would change pH
    – Escoce
    Nov 1, 2019 at 14:01

1 Answer 1


RIMS can denature your enzymes.

The biggest risk with a RIMS is the small volume or wort that is heated at a time. The result is often the enzymes are denatured because of the contact with the heating element.

This can be limited or even completly overcome by moving the wort faster through the RIMS. Also the temp probe for the heating element should be as close to the heating element as possible and use a short delay on the PID. Then its much easier to not allow the wort in RIMS heater to hit denaturing temperatures.

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