Solar water heating system having a drain back

摘要

The solar water heating system comprises a solar panel 15 arranged in a solar loop, the solar panel having an inlet and an outlet connected to an egress flow portion and return flow portion 22, respectively, of the solar loop. The solar loop contains a fluid and is arranged to circulate the fluid into the inlet of the solar panel, through the solar panel and out of the outlet of the solar panel. The system further includes a vent pipe 20 connected to the return flow portion of the solar loop. Circulation may be provided by a pump 18. The connection between the vent pipe and the return flow portion may comprise a T-junction 21, whereby circulation of the fluid by the pump results in friction between the fluid and the vent pipe, causing the fluid to rise to a fluid level 23 in the vent pipe. The friction may be stopped when the pump is stopped, allowing air to freely enter the system so that the fluid drains from the solar panel. The system may include a header tank 10, and an insulated storage tank 11. The system protects the fluid from overheating or freezing during power failure.