Principle of photovoltaic panel drain valve

What are the advantages of a drain-back Solar System?

The advantages of the drain-back solar system are: In a pressurised solar system, the solar circuit is completely filled with liquid at all times, including overnight in freezing weather and during periods of stagnation.

How do solar panels work?

The level of fluid in the drain-back vessel is lowered until the point where liquid has filled all of the pipe-work above the drain-back vessel. The circuit is now complete and heat is transferred from the solar panel to the hot water cylinder.

How does a solar panel heat pump work?

The circuit is now complete and heat is transferred from the solar panel to the hot water cylinder. When the pump switches off (for example at night time or if the cylinder reaches its target temperature), the fluid flows backwards under gravity down the solar panel until both sides reach the resting fill level again.

How does a solar pump work?

If there is heat to be collected from the solar panel, the pump is energised by the solar controller, and starts to push liquid up and over the top of the circuit. The level of fluid in the drain-back vessel is lowered until the point where liquid has filled all of the pipe-work above the drain-back vessel.