[alrbachert@gmail.com]

I have created my own RIMS system using my mash tun and kettle with a pump and PID controller.  I have copper tubbing running through a hot water bath in the kettle during the mash.  I use the pump and PID controller with temperature gauge in the mash to pull wort from the mash tun via the pump and through the heated copper coils in the kettle before returning to the mash.  While both Mash tun and Kettle are separately propane fired, I normally do not fire up the mash tun except to mash out.

I have been having some issues recently when I am not hitting my target post mash gravities.  I am wondering if running the RIMS through the kettle which is heated to 180 F to 200 F is causing the wort to heat up too much.  Has anyone come across issues like this?  Do I need to dial back the hot water bath in the kettle and run the pump more to control the mash temperature? 

[allenhuerta]

If I'm reading it right, sounds more like a HERMS, but yeah, I would never let my HLT get too far above the temp I wanted my mash. At Mash Out I'd heat it to the temps you mentioned but not before.

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[mabrungard]

If the wort is heated above the ideal enzymes temperature at any time, the enzyme lifespan is shortened. I once had poor temperature control in my RIMS and I ended up with a bunch of batches that were overly sweet, underattenuated, and worty tasting.

[ynotbrusum]

The heat of the coil immersed in the water bath should be no more than a couple degrees above the intended mash step temp.  Measure the mash temp through the course of the mashing to assure you stay within the mash guidelines intended for the beer (140’s to mid 150’s typically).  Beta amylase starts to denature in the low 150’s and alpha amylase denatures in the upper 150’s:

https://byo.com/article/understanding-enzymes-homebrew-science/

Cheers.