[Richard R.]

Hello all,
 
I have an SS Brewtech HERMS that I've been using for about 1.5 years.  Lately I've noticed I'm getting low attenuation.  I use plenty of yeast (generally 2 bags of yeast with two starters), oxygenate the wort, and try and stay right at 154 degrees for the mash.  My last batch got 67% on Omega 402 Cosmic Punch which should be 71-75%.  The others are very similar.

Could the culprit be that in my herms coil the temp is set to around 164 to keep the mash at 154.  Could the wort flowing through at that temp cause the high temps to make attenuation bad?  This has been a real head scratcher for me...

Any help greatly appreciated.

Thanks,
Richard

[lupulus]

Mash at 148F.
In The Modern Brewhouse I posted the coastdown mash.
See Musings on Mashing.
Cheers!

"It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." - Sherlock Holmes (A. Conan Doyle)

[chinaski]

You should also verify with a good thermometer that the mash temps are what the unit thinks they are.  Maybe a sensor is going bad?

[ynotbrusum]

Use a good, calibrated thermometer.  Try doing a single infusion mash - at 149-150.  Warm the tun in advance, mash for 90 minutes and stir well about 3 times during the mash.  If that results in better attenuation, then it likely is a problem with the recirc temperature.  164 seems a bit high, but not crazy high for HERMS.