going to keep it short, crazy day, but nodemcu spliced into my geyser wise, 2 x NO x 2 NC contactor that switches between eskom and offgrid solar, node controls that(via Home assistant, node running esphome) plus can use the node to switch geyser wise on and off, it also has a 220v relay used as a switch to tell HA that geyserwise is on or off.
safeties on eskom is geyserwise plus standard old thermal thing set at 10 deg higher than GW(55, actual 51C).
Safety on solar is only the standard thermal disconnect(do test them they do fail, build in safety in HA aswell)
i tried to splice into the ntc of the GW, but get more accurate readings from a ds18b20 senor, my tank has 2 jackets so one is for the thermal probe other one has ds18b20 and extra ntc i was testing, then i also have a ds18 on the out of the geyser so have top and bottom temps.
I still need to do some node red things to make it more efficient but have other priorities atm.
I might redo as i need more controll(extra relay from nodemcu to control GW, few more probes like water sensor in geyser pan ect)
some pics
