I am in Australia - and am about to book a flight !!
I would suggest that you have something completely independent of NR that could perform a master off type function and acts as a supervisor to the system - in my mind something like a Tasmota TH16 that monitored all the temps - independently of the other systems - running say Tasmota with Rules - so no Node Red involvement - simple rules - like if Temp > xyz (safe limit) - generate an alert and shut down a master ssr that shuts off everyting if it does not hear from someone in X period of time
Its all the edge use cases that you do not think of that come back and bite you - i have had instances where my boiler (gas) for hydronic heating - stopped responding to on/off commands - but only in a very weird combination - so i was pushing solar heated hot water (much lower temp) into our buffer tank and the Gas boiler was trying to raise this to some ridiculous temperature. All because of a power failure and then a WIFI access point not starting up correctly
Craig
