Currently, for those haven't seen my build thread, my build has three 26 gal kettles, the usual HLT-MT-BK, with LP Gas fire burners for HLT and BK.
My system is following the HERMS approach, with a ss coil into the HLT and the target temperature for the wort steps is reached recirculating the wort into the coil in the heated HLT water.
Looking around other builds and after some batches, I'm planning to add a 4th kettle, just for the HERMS coil, smaller in size compared to the other kettle. This kettle will have an electrical heating element to reach and maintain the target temperature.
This should reduce the time to reach each target temperature during the mashing and for sure will optimise the flow length for the wort during the HERMS recirculation.
My doubt is about the right size of the HERMS dedicated kettle and the inside coil, since right now my pots are 26 gal each, but It could be I'll double their capacity in the next future.
What do you think?