HERMS-like mashing system with heat exchange coil in mash?

Hello. Recently joined new member and first time poster here. My buddy and I mash in a 10-gal Gott cooler, and we’ve become frustrated with our lack of temperature control. Though we are happy with heat retention capability of the tun, we’d like to do step mashes with some recipes, because decocting makes me want to tear my hair out. So we started looking into RIMS and HERMS systems, but we didn’t have the money to spend on those. We wondered about sticking a copper coil in the mash. Via in/out ports drilled into the tun, the coil would be connected to a pump, which would pump hot water from a HLT. We realize this is a similar concept as a HERMS, but we would be pumping water, not wort, and the copper coil heat exchanger would sit in the mash.

I have seen very little about this approach in my research and talking to other brewers. Has anyone tried this? Is this totally nuts? Is there some totally obvious flaw we are overlooking?

We’d appreciate your feedback.

I couldn’t see why i won’t work but i think you wil need constand stirring of the mach to make sure the mash is evenly heated thru.

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It’s going to be really hard to get the mash to heat evenly.  You’d need a thin mash and constant stirring, which will then lead to heat loss.  Try it, but you might be frustrated by the result.

Only one thing that I didn’t understand, if you have a coil and a pump, why dont u run the wort into it and just put the coil in your HLT, the temperature control for that is not rocket science, is no need for a PID or anything fancy.
Just stick a thermometer on the output of the coil and you are good to go.

+1 - what you are proposing won’t be much less expensive if at all.