Charging a high-mass solar thermal heating system is much like charging a pressurized system. However, flushing all the air out is more complicated if you're running a combination system: you will need to flush each individual circuit. Always keep at least one circuit open during this procedure.
- If you have a bypass around the hot water heat exchanger, close the ball valve on that bypass half way.
- Close the valve on the shunt loop completely, pushing all flow to the heating system.
- Leave two circuits open and close the others. Allow the air bubbles to exit the system.
- Close those circuits and open the next two. Allow the air bubbles to exit the system. Repeat until all circuits are clear of air.
- Once all the floor circuits are flushed, open the shunt loop and close the floor valve.
- Pump until all the bubbles leave the system.
- Open all the circuits.