HERMS stands for Heat Exchanger Recirculating Mash System. It permits two facilities that the current system lacks. Firstly, the mash can be recirculated which means taking fluid out of the bottom of the grain bed and pumping it back to the top, effectively ‘washing’ the grains. The second is the ability to heat the liquid as we do this. This heating allows for step mashes where the temperature of the mash ‘steps’ through various temperatures at specific time points.
The way that this is going to be achieved is to build a heat exchanger into the HLT – in our case a copper coil. I picked up a 3m length of annealed copper and fashioned it into a fairly simple coil. I elected to make it vaguely cone shaped such that each loop of coil doesn’t quite sit over the one below it. My logic was that this would help prevent simply creating a band of low temperature in the HLT – whether or not this is going to make a significant difference I don’t know, but it can’t hurt!
Next a pair of threaded elbow connections were soldered onto the ends to permit me to pass the heat exchanger coil through the sidewalls of the HLT – again using the same flanged backnut and silicon baking tray washers that have been used everywhere else in the brewery.