I'd wanted to build a HERMS Hx for quite some time and in particular been mulling over how to build one so as to be as efficient as possible. I wanted a smaller rather than larger volume combined with an element of adequate power so as to minimise heating lag and end up with a more responsive Hx. Even though not ideal from a heat conductivity standpoint, I also wanted a SS coil to allow the use of caustic cleaners to my heart's content. So when I stumbled up on the HERMIT coil, the fact that it was SS and the popular PVC build required only a 2 - 3 litre capacity, I thought it looked like a winner. There was a momentary reservation regarding the 3m length of piping, but obviously everyone else was finding it no such handicap in practical terms.
The last remaining decision was whether to use the suggested 1850W kettle element or whether to upgrade to a more powerful element (I'd been considering a 2400W or better for my pre-HERMIT ideas on a Hx). In the end, I built one of these................a twin engine model, just for fun.
For a couple of years I'd perserverred with a totally inadequate 1800W 20L urn as a HLT. It annoyed me no end (understatement) whenever I was caught out with not enough water at the appropriate temp and it taught me a valuable lesson. I vowed that from then on any system upgrade would have more rather than less power. So that's why a 3700W Hx. And besides, I thought it would be interesting to carry out a comparison with either one or two elements running. Not sure I'll bother, though. Ran a water test and PID auto-tune a couple of nights ago and achieved better than 2.5 deg/min ramps. Quite impressive, I thought, and so much for any reservations regarding a 3m coil length.
Maiden HERMS brew coming this wk end, but so far I reckon my new HERMIT Hx is a ripper.
