I decided to use an Arduino for the controls. Since I wanted to integrate the solar with my heating system, I figured it would give me plenty of flexibility. I知 using one wire DS18B20 digital temp sensors for the inputs and a relay board (
http://arduino-info.wikispaces.com/ArduinoPower) to control the pumps and furnace. There are four relays, one for the solar loop pump, one for the furnace loop pump, one to turn on the furnace fan, and the last is in parallel with my house thermostat. This allows three modes of operation for heating the house.
First mode/stage would be solar only. The water in the tank is hot enough to comfortably heat the return plenum air, so just the circulating pump and the furnace fan are switched on. Second stage is if the stored water is still warm, but not sufficient to provide all of the heat to maintain the house temperature. The oil burner will switch on, but I値l also keep the circulating pump on. Third stage the water has cooled down to a point where it is pointless to circulate it. I値l switch off the pump relay, and keep the oil burner on.
I also bought an Ethernet shield to hook everything up to the internet. I got most of the programming from Nateful痴 Differduino site:
Arduino Differential Controller | Arduino Solar Hot Water | Differduino | Nateful . I知 connected into Xively (previously Cosm, previously Pachube) to log data and can also control the thermostat set-point and pumps remotely. You can see the feeds here:
https://xively.com/feeds/42603
Most of them aren稚 hooked up yet, I知 kind of controlling things manually for now until I have everything set-up. Wiring is also still a bit messy.
