Solar and underfloor heating
Heating regulator was built for floor heating and later extended for
solar heating. Lacking of standard regulators capable of driving up to
four independent circuits I have decided to build one of my own.
Heating system description
The project power of the boiler is 17kW. As we decided for floor
heating, I wanted to controll each flat temperature with mixing
valve. 4-way mixing valves are necessary for floor heating because
return temperature is too low to be directcy drawn into boiler return.
Hot water is transported from dividing bridge through the ground from
garage with duct to house. Duct is made of 100mm styrofoam in
rectanqular cross-section of 300x400mm. Duct has 3 forward, 3 return
PEX pipes of 25x2.3mm diameter. Warm and cold pipes are separated with
10mm EPS. Duct also holds two 16x2m sanitar hot water pipes for
circulation. The length of the duct is 11m. Every flat has its own
Solar and underfloor heating regulation controller
Software is divivided into this main parts:
Binary code is approx 16KB in size and >3000 lines of source code.
- Four independent underfloor circuits driving
- Outdoor temperature driving model
- DHW tank independent controlling
- Hot water supply timed circulation
- Circulation between solar tank and DHW tank for greater efficiency
- Night time procedures with RTC
- Display blanking
- Counting of burner operating time
- Solar pump driver
- 1-wire Dallas digital thermometers
- Pump long time protection
- Legionella safe mode
Some LOG files and plots from operation of the controllereare available .
Last modified: Wed Apr 20 11:23:34 CEST 2005