I have to say, really pleased with BrewBlox so thanks to everyone who contributed.
I use the same Pi and Spark combo to control the HERMS and then control the boil in the Kettle - it’s a bit of a faff with BrewPi but it’s worked really well. I have one ‘SSR control box power supply’ and have been switching between mashing and boiling by simply switching the power supply cable from the HLT to the Kettle and then tweaking the values in BrewPi. This seems a lot easier with BrewBlox but of course I have just one DS2413 output wired in to the single SSR. BrewBlox won’t let me have the same output widget assigned to the two vessels.
Question - can I wire both DS2413 outputs A&B to the same input of the SSR? In this case, if output pin A is ON, then output B would see that voltage and vice versa - will this spanner things? Or is there a more elegant solution?