Tinycontrol LAN Controller managing backup electric immersion heater. Plus data logging temperature! Idea is to log hot water use and heating - Settings heating schedules to save money based on these. Temp is taken approx 20inches below top of tank. 14
Uses Raspberry Pi with Dallas DS18B20 sensors and BMP180 for pressure. Uses udp comms to Wemos D1 mini for switching relays for pump and pond heater. Monitors Koi pond temperature and shack (with water pipes in loft) sending email and ThingTweet update
Using an ESP8266 ESP-01 module and an Arduino Pro Mini 3.3V I wirelessly update all outputs from my thermostat to here for data analysis and because it's cool. This requires a voltage divided rectifier since thermostats run at least 24 VAC RMS.