this is why it is very important to size your cyclinder and the amout of collectors you need. Even when sized correctly it still can be a problem tho i admit.lcgs said:The main problem with solar is stagnation. this is where the pump stops and the fluid turns to steam, by ensuring that the water in the cylinder is at low temps all the time your system will stagnate very quickly.Stagnation causes abreakdown of the glycol mix which you will have to change more frequently.
On mine once the panles have got to 120deg c you can divert the heat to another source via a second pump. You can either pump it to a swimming pool via a heat exchange or another cyclinder. Thing is i don't have a swimming pool or a second cyclinder. I'm thinking of adding a smaller single coil indirect cylinder to the system to heat up once the first cylinder is heated to try and stop this stagnation and link both cylinders together in series.